“ pharmaceutically acceptable salt ” refers to those salts which retain the biological effectiveness and properties of the free bases and which are obtained by reaction with inorganic acids such as hydrochloric acid , hydrobromic acid , sulfuric acid , nitric acid , phosphoric acid , methanesulfonic acid , ethanesulfonic acid , p - toluenesulfonic acid , salicylic acid and the like . “ alkyl ” refers to a straight - chain , branched or cyclic saturated aliphatic hydrocarbon . typical alkyl groups include methyl , ethyl , propyl , isopropyl , butyl , isobutyl , tertiary butyl , pentyl , hexyl and the like . the alkyl group may be optionally substituted with one or more substituents selected from the group consisting of hydroxyl , cyano , or alkoxy . when the alky group is an r ′ substituent , it is a lower alkyl of from 1 to 6 carbons , more preferably 1 to 4 carbons . “ aryl ” refers to an aromatic group which has at least one ring having a conjugated pi electron system and includes carbocyclic aryl , heterocyclic aryl and biaryl groups . the aryl group may be optionally substituted with one or more substituents selected from the group consisting of halogen , trihalomethyl , hydroxyl , sh , oh , no 2 , amine , thioether , cyano , alkoxy , alkyl , and amino . examples of aryl groups include phenyl , napthyl and anthracyl groups . phenyl and substituted phenyl groups are preferred . “ heteroaryl ” refers to an aryl group having from 1 to 3 heteroatoms as ring atoms , the remainder of the ring atoms being carbon . heteroatoms include oxygen , sulfur , and nitrogen . thus , heterocyclic aryl groups include furanyl , thienyl , pyridyl , pyrrolyl , n - lower alkyl pyrrolo , pyrimidyl , pyrazinyl , imidazolyl and the like . all reactions were carried out in dry glassware under an atmosphere of argon unless otherwise noted . reactions were purified by column chromatography , under medium pressure using a biotage sp4 or by preparative high pressure liquid chromatography . 1 h nmr was recorded on a bruker 400 mhz instrument . spectra are reported as ppm δ and are referenced to the solvent resonances in cdcl 3 , dmso - d 6 or methanol - d 4 . all solvents were purchased from sigma - aldrich . reagents were purchased from sigma aldrich , bachem , akaal , fisher , alfa aesar , acros and anaspec . the following abbreviations are used methylene chloride ( dcm ), ethyl acetate ( ea ), hexanes ( hex ), dichloroethane ( dce ), dimethyl formamide ( dmf ), trifluoroacetic acid ( tfa ), tetrahydrofuran ( thf ), carbonyldiimidazole ( cdi ), dimethylaminopyridine ( dmap ), triethyl amine ( tea ), methyl trifluoromethanesulfonate ( meotf ), ( s )- 2 - amino - 6 -( bis - pyridin - 2 - ylmethyl - amino )- hexanoic acid ( dpk ), glutamic acid ( glu ), diisopropylethylamine ( diea ), benzyloxycarbonyl ( cbz ). the following compounds were all prepared in overall yields ranging from 20 - 40 % following the route depicted in scheme 1 . the first step , performed at 0 ° c . under inert conditions used the di - t - butyl ester of glutamic acid with cdi in the presence of base to form the intermediate glu - urea - imidazole derivative 2 . this intermediate was activated with meotf under basic conditions to afford the methylated imidazole 3 , which under inert conditions reacted readily with amines . the tert - butyl ester protecting groups were removed using 20 % tfa in dcm for 1 to 4 hour at room temperature . upon completion of the deprotection , the reactions were concentrated on a rotary evaporator or blown dry with nitrogen and purified on a silica column or recrystallized . the final products were tested in vitro and in vivo . to a suspension of di - t - butyl glutamate hydrochloride ( 15 . 0 g , 51 mmol ) in dcm ( 150 ml ) cooled to 0 ° c . was added tea ( 18 ml ) and dmap ( 250 mg ). after stirring for 5 min . cdi ( 9 . 0 g , 56 mmol ) was added and the reaction was stirred overnight with warming to room temperature . the reaction was diluted with dcm ( 150 ml ) and washed with saturated sodium bicarbonate ( 60 ml ), water ( 2 × 100 ml ) and brine ( 100 ml ). the organic layer was dried over sodium sulfate and concentrated to afford the crude product as a semi - solid , which slowly solidified upon standing . the crude material was triturated with hexane / ethyl acetate to afford a white solid which was filtered , washed with hexane ( 100 ml ) and dried to afford the desired product ( 15 . 9 g , 45 mmol , 88 %) as a white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 7 . 63 ( s , 1h ), 7 . 00 ( br , 2h ), 6 . 31 ( d , 1h ), 4 . 02 ( m , 1h ), 2 . 19 ( m , 2h ), 1 . 86 ( m , 1h ), 1 . 67 ( m , 1h ), 1 . 39 ( s , 9h ), 1 . 38 ( s , 9h ). esms m / z : 354 ( m + h ) + . alternatively , the analogs can be prepared via the isocyanate generated in situ using triphosgene . this approach can be accomplished by either activation of the glutamate residue and coupling with a lysine residue ( route a ) or by activating the lysine residue and coupling it with the glutamate ( route b ) as shown in scheme 2 below . route a . in a round bottom flask 1 . 8 ml tea ( 13 . 2 mmol ) was combined with 1 . 8 grams ( 6 mmol ) l - glutamic acid di - tertbutyl ester hydrochloride in 20 ml dcm . this solution is added dropwise over 45 minutes to a solution of 10 ml dcm and triphosgene ( 0 . 7 g , 2 . 2 mmol ) at 0 ° c . after stirring an additional 30 min a solution of h - lys -( z )— o - t - butyl ester hcl ( 2 . 2 g , 6 mmol ) containing tea ( 1 . 8 ml , 13 mmol ) in 15 ml dcm was added in one portion . the solution was stirred for 1 hour . the reaction is concentrated , diluted with 50 ml ethyl acetate , washed 2n nahso4 ( 2 × 50 ml ), brine ( 50 ml ) and dried over sodium sulfate to yield a yellow oil . purification by column chromatography to afford the desired product as a clear oil which upon standing solidifies to a white solid ( 1 . 9 g , 54 %). route b . in a round bottom flask triphosgene ( 2 . 9 g , 10 mmol ) is suspended in dcm ( 50 ml ) and stirred at 0 ° c . a solution of h - lysine ( z ) freebase ( 9 . 1 g , 27 mmol ) and diea ( 10 . 4 ml , 60 mmol ) dcm ( 50 ml ) was added dropwise to the triphosgene solution over 2 . 5 hours . after 2 . 5 hours a solution of l - glutamic acid di - tertbutyl ester hydrochloride ( 8 g , 27 mmol ) containing dma ( 10 . 4 ml , 60 mmol ) dcm ( 50 ml ) was added in one portion and allowed to stir for 45 minutes . the reaction was concentrated to dryness , diluted with 150 ml ethyl acetate , washed with 2n nahso 4 ( 2 × 200 ml ), brine ( 150 ml ) and dried over sodium sulfate to yield a yellow oil . this oil was purified by column chromatography ( sio 2 ) to afford the desired product as a clear oil which upon standing solidifies to a white solid ( 12 . 0 g , 72 %). 1 h nmr ( 400 mhz , cdcl 3 ) δ 7 . 34 ( m , 5h ), 5 . 33 - 5 . 28 ( m , 3h ), 5 . 08 ( d , j = 7 . 4 hz , 2h ), 4 . 38 - 4 . 29 ( m , 2h ), 3 . 15 ( m , 2h ), 2 . 32 - 2 . 01 ( m , 2h ), 1 . 90 - 1 . 50 ( m , 8h ), 1 . 43 - 1 . 40 ( m , 27h , t - bu &# 39 ; s ). esms m / z : 622 ( m + h ) + . to a solution of 2 -[ 3 -( 5 - benzyloxycarbonylamino - 1 - tert - butoxycarbonyl - pentyl )- ureido ]- pentanedioic acid di - tert - butyl ester ( 630 mg , 1 . 0 mmol ) in ethanol ( 20 ml ) was added ammonium formate ( 630 mg , 10 eqv ) followed by 10 % pd — c and the suspension was allowed to stand with occasional agitation overnight until complete . the reaction was filtered through celite and concentrated to afford the desired product ( 479 mg , 98 %) as a waxy solid . 1 h nmr ( 400 mhz , cdcl 3 ) δ 7 . 15 - 6 . 0 ( bm , 4h , nh &# 39 ; s ), 4 . 29 ( m , 2h ), 3 . 02 ( m , 2h ), 2 . 33 ( m , 2h ), 2 . 06 - 1 . 47 ( m , 8h ), 1 . 45 - 1 . 40 ( m , 27h , t - bu &# 39 ; s ). esms m / z : 488 ( m + h ) + . in this series a tether is incorporated onto the side chain of glutamic acid or lysine prior to conjugation to form the urea dimer . in the example below the side chain carboxylic acid of one of the glutamic acids is modified into a tether to append a chelator , atom or functional group that is or contains a radionuclide ( scheme 4 ). to a solution of n — boc glutamic acid α - methyl ester boc - glu ( oh )- ome ( 960 mg , 3 . 7 mmol ) in dmf ( 6 ml ) cooled to 0 ° c . was added edc ( 845 mg , 1 . 3 eqv ) and tea ( 1 . 3 ml ). after stirring for 10 min the mono protected diamine n — cbz - 1 , 4 - diaminobutane hydrochloride salt ( 1 g , 3 . 8 mmol ) was added and the reaction is allowed to stir overnight with warming to room temperature . the crude reaction was diluted with ea ( 100 ml ) and washed with and washed with water ( 30 ml ), 5 % aq . citric acid ( 30 ml ), sat . sodium bicarbonate ( 30 ml ), water ( 30 ml ) and brine ( 30 ml ). the organic layer was dried over sodium sulfate and concentrated to afford the crude product as a thick syrup ( 2 . 1 g ). to the obtained syrup was added 4 n hcl in dioxane ( 10 ml ) and the reaction was stirred at room temperature for 3 h . concentration afforded a waxy solid ( 1 . 8 g ) as the hydrochloride salt . the salt was coupled to the activated l -( s )- 2 -[( imidazole - 1 - carbonyl )- amino ]- pentanedioic acid di - tert - butyl ester ( 2 ) as described in the preceding experimental sections to afford the desired fully protected dimer x ( 1 . 9 g ). this material was suspended in absolute etoh ( 20 ml ) excess ammonium formate ( 5 g ) added followed by 20 % pd ( oh ) 2 on carbon ( 100 mg ) and the suspension very gently agitated overnight to effect cleavage of the cbz protection group . filtration through celite and concentration afforded the desired free amine ( 1 . 4 g , 2 . 7 mmol , 73 %, 4 steps ). 1 h nmr ( 400 mhz , cdcl 3 ) 8 . 41 ( br , 2h ), 7 . 36 9br , 1h ), 6 . 44 ( bs , 1h ), 6 . 37 ( bs , 1h ), 4 . 37 - 4 . 29 ( m , 2h ), 3 . 71 ( s , 3h ), 3 . 20 - 1 . 50 ( m , 16h ), 1 . 45 ( s , 9h ), 1 . 43 ( s , 9h ). esms m / z : 517 ( m + h ) + . the protected intermediate was prepared by reductive amination using pyridine - 2 - carboxaldehyde as previously described . treatment with 2m lioh in meoh effected hydrolysis of the methyl ester . the methanol was removed and excess dcm : tfa ( 1 : 1 ) was added and the reaction stirred at room temperature overnight . the crude material was converted into the desired rhenium conjugate following the procedure described above . preparative hplc afforded the desired molecule ( 9 . 5 mg , 16 %). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 78 ( m , 2h ), 8 . 31 ( br , 1h ), 7 . 95 ( m , 2h ), 7 . 59 ( m , 2h ), 7 . 39 ( m , 2h ), 6 . 60 - 6 . 33 ( m , 2h ), 4 . 89 ( m , 4h ), 4 . 00 ( m , 1h ), 3 . 76 ( m , 1h ), 3 . 20 - 1 . 2 ( m , 16h ) ( 3 co 2 h not seen ). esms 842 ( m − h ) + . the following compounds were all prepared in overall yields ranging from 20 - 40 % usin the route depicted in scheme 3 . the z - deprotected glu - urea - lysine was mixed with the appropriate aldehyde ( 0 . 9 equivalents ) at room temperature for one hour to form the □ chiff base intermediate . the □ chiff base was reduced using 1 equivalent of sodium triacetoxyborohydride . the compounds were deprotected using 50 % tfa in dcm for 1 hour at room temperature . upon completion , the reactions were concentrated on a rotary evaporator or were blown dry with nitrogen and extracted using methylene chloride and water . the water layer was evaporated to dryness to afford the deprotected product in 40 - 80 % yield . to a solution of 4 - iodobenzaldehyde ( 1 . 92 g , 8 . 27 mmol ) in dry dioxane ( 60 ml ) was added hexamethylditin ( 4 . 1 ml , 19 . 8 mmol ) followed by pd ( ph 3 p ) cl 2 ( 150 mg ) and the reaction mixture was heated for 3 h under reflux until judged complete . the reaction was filtered through celite and purified by column chromatography using hexanes / ethyl acetate ( 9 / 1 ) as eluent to afford ( 2 . 24 g , 98 %) as a clear oil . 1 h nmr ( 400 mhz , cdcl 3 ) δ 9 . 97 ( s , 1h ), 7 . 81 ( d , j = 7 . 8 hz , 2h ), 7 . 72 ( d , j = 7 . 8 hz , 2h ), 0 . 29 ( s , 9h ). esms m / z : 268 ( sn - cluster ). to a solution of 2 -[ 3 -( 5 - amino - 1 - tert - butoxycarbonyl - pentyl )- ureido ]- pentanedioic acid di - tert - butyl ester ( 150 mg , 0 . 31 mmol ) in dce ( 10 ml ) was added 4 - trimethylstannanyl - benzaldehyde ( 82 mg , 0 . 31 mmol ) followed by sodium triacetoxyborohydride ( 98 mg , 0 . 47 mmol ) and the reaction was stirred overnight at 40 ° c . the reaction was concentrated and purified by column chromatography using hexanes / ethyl acetate as eluent to afford the desired product ( 88 mg , 38 %) as a thick syrup which begins to solidify upon standing . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 7 . 48 ( d , j = 7 . 4 hz , 2h ), 7 . 30 ( d , j = 7 . 4 hz , 2h ), 6 . 27 ( m , 2h , nh &# 39 ; s ), 3 . 96 ( m , 4h ), 2 . 74 ( bm , 2h ), 2 . 21 ( m , 2h ), 1 . 87 ( m , 2h ), 1 . 65 - 1 . 19 ( m , 7h ), 1 . 35 ( m , 27h , t - bu &# 39 ; s ), 0 . 23 ( s , 9h ). esms m / z : 742 ( sn - cluster ). the same experimental procedure as depicted in scheme 1 , yielded 8 % of 2 -[ 3 -( 5 - benzyloxycarbonylamino - 1 - tert - butoxycarbonyl - pentyl )- ureido ]- pentanedioic acid di - tert - butyl ester . the compound was deprotected using the previously described methods and purified by hplc to afford the desired product . 1 h nmr ( tri - t - butyl ester of z - protected amine ) ( 400 mhz , cdcl 3 ,) δ 12 . 2 ( s , 3h ), 6 . 4 ( s , 2h ), 4 . 15 ( m , 2h ), 3 . 45 ( m , 1h ), 2 . 75 ( bs , 1h ), 2 . 2 ( m , 4h ), 1 . 90 ( m , 2h ), 1 . 65 ( m , 2h ), 1 . 50 ( s , 2h ), 1 . 35 ( m , 2h ). esms m / z : 622 ( m − h ) + . the same experimental procedure as in the general synthesis , yielded 0 . 65 g , 48 % of 2 -( 3 , 3 - bis - pyridin - 2 - ylmethyl - ureido )- pentanedioic acid di - tert - butyl ester . the compound was deprotected using the previously described methods and purified by hplc to afford the desired product . 1 h nmr ( 400 mhz , dmso - d 6 ) δ , 12 . 0 ( bs , 2h ), 8 . 68 ( d , 2h ), 8 . 00 ( m , 2h ), 7 . 41 ( d , 4h ), 7 . 14 ( d , 1h ), 4 . 73 ( d , 4h ), 3 . 96 ( s , 1h ), 2 . 18 ( m , 2h ), 1 . 80 ( m , 2h ). the same experimental procedure as in the general synthesis in scheme 1 , yielded 0 . 16 g , 35 % of 2 -{ 3 -[ 3 -( bis - pyridin - 2 - ylmethyl - amino )- 1 - carboxy - propyl ]- ureido }- pentanedioic acid di - tert - butyl ester . the compound was deprotected using the previously described methods and purified by hplc to afford the desired product . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( br , 2h ), 9 . 37 ( s , 1h ), 8 . 52 ( d , 2h ), 7 . 80 ( t , 2h ), 7 . 14 ( dd , 4h ), 6 . 45 ( m , 2h ), 4 . 49 ( br , 4h ), 4 . 12 ( s , 1h ), 4 . 05 ( s , 1h ), 3 . 21 ( m , 2h ), 2 . 24 ( m , 2h ), 1 . 80 ( m , 2h ), 1 . 40 ( m , 2h ). the same experimental procedure as in the general synthesis , yielded 0 . 09 g , 12 % of 2 -{ 3 -[ 5 -( bis - pyridin - 2 - ylmethyl - amino )- 1 - carboxy - pentyl ]- ureido }- pentanedioic acid di - tert - butyl ester . the compound was deprotected using the previously described methods and purified by hplc to afford the desired product . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 7 ( s , 2h ), 8 . 97 ( s , 1h ), 8 . 65 ( dd , 2h ), 7 . 91 ( dd , 2h ), 7 . 45 ( m , 4h ), 6 . 44 ( d , 1h ), 6 . 28 ( d , 1h ), 4 . 45 ( br , 4h ), 4 . 10 ( m , 2h ), 3 . 15 ( br , 2h ), 2 . 60 ( m , 2h ), 2 . 25 ( m , 2h ), 1 . 90 ( m , 2h ), 1 . 78 ( m , 2h ), 1 . 45 ( m , 2h ). the same experimental procedure as in the general synthesis , yielded 0 . 038 g , 5 % of 2 -{ 3 -[ 1 - carboxy - 2 -( 4 - iodo - phenyl )- ethyl ]- ureido }- pentanedioic acid di - tert - butyl ester . the compound was deprotected using the previously described methods . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 40 ( s , 3h ), 7 . 65 ( dd , 2h ), 7 . 05 ( dd , 2h ), 6 . 30 ( m , 2h ), 4 . 25 ( s , 1h ), 4 . 05 ( s , 1h ), 2 . 90 ( m , 2h ), 2 . 2 ( m , 2h ), 1 . 80 ( m , 2h ). esms m / z : 429 ( m ) + , 451 ( m + na ). the same general procedure , using the previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods ( 5 . 5 mg , 66 %). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( s , 3h ), 8 . 8 ( s , 1h ), 7 . 94 ( m , 1h ), 7 . 5 ( m , 1h ), 7 . 16 ( t , 1h ), 6 . 38 ( m , 2h ), 4 . 15 ( m , 5h ), 3 . 06 ( s , 2h ), 2 . 85 ( s , 1h ), 2 . 2 ( m , 2h ), 1 . 90 ( m , 1h ), 1 . 70 ( m , 2h ), 1 . 50 ( s , 2h ), 1 . 35 ( m , 2h ). esms m / z : 536 ( m + h ) + . the same general procedure , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di - t - butyl ester . the compound was deprotected using the previously described methods ( 4 . 1 mg , 53 %). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( s , 3h ), 8 . 7 ( s , 2h ), 7 . 9 ( s , 1h ), 7 . 8 ( d , 1h ), 7 . 44 ( d , 1h ), 7 . 22 ( t , 1h ), 6 . 25 ( s , 2h ), 4 . 09 ( m , 5h ), 2 . 89 ( s , 1h ), 2 . 75 ( s , 1h ), 2 . 2 ( d , 2h ), 1 . 90 ( m , 2h ), 1 . 65 ( m , 2h ), 1 . 40 ( m , 2h ). the same general procedure , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods ( 12 mg , 66 %). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( bs , 3h ), 8 . 8 ( br , 1h ), 7 . 8 ( d , 2h ), 7 . 27 ( d , 2h ), 6 . 35 ( br , 2h ), 4 . 1 ( m , 4h ), 2 . 89 ( m , 2h ), 2 . 2 ( d , 2h ), 1 . 90 ( m , 2h ), 1 . 65 ( m , 4h ), 1 . 35 ( m , 2h ). esms m / z : 536 ( m + h ) + . the same general procedure , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( br , 3h ), 8 . 7 ( br , 1h ), 7 . 5 ( m , 2h ), 7 . 3 ( m , 2h ), 6 . 35 ( m , 2h ), 4 . 1 ( m , 4h ), 2 . 9 ( m , 2h ), 2 . 2 ( d , 2h ), 1 . 90 ( m , 2h ), 1 . 60 ( m , 4h ), 1 . 35 ( m , 2h ). esms m / z : 428 ( m + h ) + , 450 ( m + na ). the same general procedure , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . 1 hnmr ( tri t - butyl ester ) ( 400 mhz , cdcl 3 ) δ 7 . 52 ( d , 2h ), 7 . 32 ( d , 2h ), 6 . 28 ( m , 2h ), 3 . 98 ( m , 2h ), 2 . 55 ( t , 2h ), 2 . 48 ( t , 2h ), 2 . 22 ( m , 2h ), 1 . 85 ( m , 2h ), 1 . 62 ( m , 2h ), 1 . 45 ( m , 2h ), 1 . 37 ( s , 27h ), 1 . 28 ( m , 2h ) esms m / z : 642 ( m + h ) + . the compound was deprotected using the previously described methods . esms m / z : 474 ( m + h ) + . the same general procedure , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 4 ( s , 3h ), 8 . 45 ( s , 1h ), 7 . 8 ( dd , 2h ), 7 . 6 ( dd , 2h ), 6 . 3 ( s , 2h ), 5 . 75 ( s , 1h ), 4 . 1 ( m , 4h ), 3 . 2 ( s , 2h ), 2 . 25 ( d , 2h ), 1 . 90 ( m , 1h ), 1 . 65 ( m , 2h ), 1 . 4 ( m , 2h ). in a round bottom flask 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester ( 300 mg , 0 . 62 mmol ) is suspended in water ( 10 ml ) and 1 , 4dioxane ( 10 ml ) and tea ( 1 . 75 ml , 1 . 25 mmol ) was added followed by 4 - iodo - benzenesulfonyl chloride and the mixture stirred overnight at 50 ° c . the reaction mixture was evaporated to dryness , taken up in dcm and chromatographed over silica gel to afford the desired product ( 375 mg , 80 %) as a clear oil . the compound was deprotected using the previously described methods followed by hplc purification to afford the desired product mip - 1097 as a whiter solid ( 270 grams , 90 % yield ). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 7 . 97 ( d , 2h ), 7 . 68 ( t , 1h ), 7 . 53 ( d , 2h ), 6 . 35 ( dd , 2h ), 4 . 10 ( m , 1h ), 4 . 00 ( m , 1h ), 2 . 65 ( m , 2h ), 2 . 22 ( m , 2h ), 1 . 9 ( m , 1h ), 1 . 7 ( m , 1h ), 1 . 55 ( m , 1h ), 1 . 45 ( m , 1h ), 1 . 35 ( m , 2h ), 1 . 25 ( m , 2h ), ( 3 co 2 h not seen ). esms m / z : 565 ( m + h ) + . in a round bottom flask 4 - iodo - phenyl isocyanate ( 100 mg , 0 . 41 mmol ) is dissolved in dcm ( 10 ml ) containing tea ( 0 . 057 ml , 0 . 4 mmol ). 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester ( 200 mg , 0 . 41 mmol ) was added and stirred for 3 hours . the reaction mixture was evaporated to dryness and the crude mixture taken up in methanol ( 5 ml ). dropwise addition to water ( 20 ml ) afforded a white precipitate which was collected and washed with water ( 20 ml ) and dried to afford the desired tri - tert butyl ester as a white solid which was deprotected directly using the previously described method to afford the desired product ( 158 mg , 53 %) as a white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 51 ( s , 1h ), 7 . 5 ( d , 2h ), 7 . 22 ( d , 2h ), 6 . 3 ( t , 2h ), 6 . 16 ( t , 1h ), 4 . 05 ( m , 2h ), 3 . 05 ( m , 2h ), 2 . 24 ( m , 2h ), 1 . 9 ( m , 1h ), 1 . 68 ( m , 2h ), 1 . 52 ( m , 1h ), 1 . 38 ( m , 2h ), 1 . 28 ( m , 2h ), ( 3 co 2 h not seen ). esms m / z : 565 ( m + h ) + . malonic acid ( 2 . 2 g , 21 . 5 mmol ) and 3 - iodobenzaldehyde ( 5 g , 21 . 5 mmol ) were suspended in ethanol ( 50 ml ) and ammonium acetate ( 1 . 66 g , 21 . 5 mmol ) was added and the reaction heated to a reflux overnight . the reaction was cooled to room temperature filtered and washed with ethanol followed by ether and dried to afford the product ( 3 . 4 g , 11 . 6 mmol , 54 %) as a white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 7 . 80 ( s , 1h ), 7 . 64 ( dd , j = 7 . 8 hz , 1h ), 7 . 42 ( dd , j = 7 . 6 hz , 1h ), 7 . 16 ( dd , j = 7 . 8 hz , 1h ), 7 . 14 ( dd , j = 7 . 6 hz , 1h ), 4 . 21 ( m , 1h ), 2 . 36 ( m , 2h ). to a suspension of (±)- 3 - amino - 3 -( 3 - iodo - phenyl )- propionic acid ( 3 . 1 g , 10 . 6 mmol ) in methanol was added thionyl chloride ( 0 . 95 ml , 12 . 7 mmol ) and the reaction was stirred at room temperature overnight . concentration followed by trituration with ether gives a white solid . the solid is filtered , washed with ether and dried to afford the desired product ( 3 . 5 g , 10 mmol , 95 %) as a white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 79 ( br , 2h ), 8 . 01 ( s , 1h ), 7 . 74 ( d , j = 8 . 1 hz , 1h ). 7 . 57 ( d , j = 7 . 8 hz , 1h ), 7 . 21 ( dd , j = 8 . 1 , 7 . 8 hz , 1h ), 4 . 56 ( br , 1h ), 3 . 54 ( s , 3h ), 3 . 23 - 3 . 17 ( m , 1h ), 3 . 04 - 2 . 98 ( m , 1h ). 2 -[( imidazole - 1 - carbonyl )- amino ]- pentanedioic acid di - tert - butyl ester ( 370 mg , 1 . 05 mmol ) was dissolved in dce ( 10 ml ) and coiled to 0 ° c . meotf ( 142 μl , 1 . 25 mmol ) was added and the reaction was allowed to proceed for 20 min . (±)- 3 - amino - 3 -( 3 - iodo - phenyl )- propionic acid methyl ester ( 356 mg , 1 . 045 mmol ) was added and the reaction was allowed to warm to room temperature and then warmed to 55 ° c . and stirred overnight . the reaction was diluted with dcm ( 50 ml ) and washed with water ( 30 ml ), 5 % aq . citric acid ( 30 ml ), sat . sodium bicarbonate ( 30 ml ), water ( 30 ml ) and brine ( 30 ml ). the organic layer was dried over sodium sulfate and concentrated to afford the crude product . the product was purified by column chromatography to afford the desired product ( 303 mg , 0 . 51 mmol , 49 %) as a white foam . 1 h nmr ( 400 mhz , cdcl 3 ) δ 7 . 66 ( s , 1h ), 7 . 57 ( d , j = 7 . 6 hz , 1h ), 7 . 29 ( s , 1h ), 7 . 07 - 7 . 02 ( m , 1h ), 5 . 74 ( br , 1h ), 5 . 17 ( br , 2h ), 4 . 30 ( m , 1 μl ), 3 . 63 ( s , 1 . 5h ), 3 . 62 ( s 1 . 5h ), 2 . 88 - 2 . 76 ( m , 2h ), 2 . 38 - 2 . 24 ( m , 2h ), 2 . 10 - 2 . 00 ( m , 1h ), 1 . 90 - 1 . 80 ( m , 1h ), 1 . 46 ( s , 9h ), 1 . 44 ( s , 9h ). to a solution of (±) 2 -{ 3 -[ 1 -( 3 - iodo - phenyl )- 2 - methoxycarbonyl - ethyl ]- ureido }- pentanedioic acid di - tert - butyl ester ( 289 mg , 0 . 49 mmol ) was dissolved in methanol ( 3 ml ) and 2m lioh ( 0 . 5 ml ) was added and the reaction stirred at room temperature overnight . the reaction was diluted with water ( 20 ml ) and the organic layer was extracted with ethyl acetate ( 2 × 20 ml ) then acidified with 1n hcl to ph ˜ 2 . the aqueous layer was extracted with ethyl acetate ( 3 × 20 ml ), dried over sodium sulfate and concentrated to afford the crude product ( 206 mg , 0 . 36 mmol , 73 %) as a white solid . to the crude material was added dcm ( 2 ml ) followed by tfa ( 2 ml ) and the reaction was stirred at room temperature overnight . concentration followed by recrystallization from ethyl acetate afforded the desired product ( 22 mg , 0 . 047 mmol , 10 %) as a white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 39 ( br , 3h ), 7 . 64 ( br , 1h ), 7 . 56 ( m , 1h ), 7 . 30 ( bm , 1h ), 7 . 10 ( bm , 1h ), 6 . 72 ( bm , 1h ), 6 . 34 ( bm , 1h ), 4 . 94 ( br , 1h ), 4 . 03 ( bm , 1h ), 2 . 64 ( br , 2h ), 2 . 20 ( br , 2h ), 1 . 86 ( br , 1h ), 1 . 71 ( br , 1h ). esms m / z : 463 ( m − h ) + . the same general procedure as shown in scheme 1 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di - t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product ( 100 mg , 45 %) as an off - white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 9 . 0 ( br , 3h ), 7 . 63 ( d , 1h ), 7 . 2 ( m , 2h ), 7 . 15 ( d , 1h ), 6 . 30 ( d , 2h ), 4 . 1 ( m , 4h ), 2 . 9 ( br , 2h ), 2 . 2 ( m , 2h ), 1 . 90 ( m , 2h ), 1 . 60 ( m , 4h ), 1 . 35 ( m , 2h ). esms m / z : 444 ( m + h ) + . the same general procedure as shown in scheme 1 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product ( 200 mg , 90 %) as an off - white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 9 ( br , 3h ), 7 . 6 ( s , h ), 7 . 43 ( m , 3h ), 6 . 39 ( br , 2h ), 4 . 1 ( m , 4h ), 2 . 9 ( br , 2h ), 2 . 2 ( m , 2h ), 1 . 90 ( m , 2h ), 1 . 60 ( m , 4h ), 1 . 35 ( m , 2h ). esms m / z : 444 ( m + h ) + . the same general procedure as shown in scheme 1 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product as ( 10 mg , 66 %) as an off - white solid . esms m / z : 444 ( m + h ) + . the same general procedure as shown in scheme 1 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product ( 5 mg , 47 %) as an off - white solid . esms m / z : 410 ( m + h ) + . in a round bottom flask phenyl isocyanate ( 100 mg , 0 . 84 mmol ) was dissolved in dcm ( 10 ml ) 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester ( 409 mg , 0 . 84 mmol ) was added and stirred for 3 hours . the reaction mixture was evaporated to dryness and the crude mixture was purified via flash column chromatography 2 : 1 hexanes / ethyl acetate to afford the tert - butyl ester as a white solid which was deprotected using tfa / ch 2 cl 2 affording the desired product . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 5 ( s , 3h ), 8 . 54 ( s , 1h ), 7 . 40 ( dd , 2h ), 7 . 26 ( dd , 2h ), 6 . 30 ( t , 2h ), 6 . 17 ( t , 1h ), 4 . 05 ( m , 2h ), 3 . 05 ( m , 2h ), 2 . 44 ( m , 2h ), 1 . 90 ( m , 1h ), 1 . 68 ( m , 2h ) 1 . 52 ( m , 1h ). 1 . 40 ( m , 2h ). 1 . 29 ( m , 2h ). esms m / z : 439 ( m + h ) + . in a round bottom flask 4 - bromo - phenyl isocyanate ( 100 mg , 0 . 50 mmol ) was dissolved in dcm ( 10 ml ). 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester ( 246 mg , 0 . 50 mmol ) was added and stirred for 3 hours . the reaction mixture was evaporated to dryness and the crude mixture was purified via flash column chromatography 2 : 1 hexanes / ethyl acetate to afford the tert - butyl ester as a white solid which was deprotected using tfa / ch 2 cl 2 affording the desired product 1 h nmr ( 400 mhz , dmso - d o ) δ 12 . 5 ( s , 3h ), 8 . 55 ( s , 1h ), 7 . 35 ( d , 4h ), 6 . 30 ( t , 2h ), 6 . 18 ( t , 1h ), 4 . 08 ( m , 2h ), 3 . 05 ( m , 2h ), 2 . 22 ( m , 2h ), 1 . 90 ( m , 1h ), 1 . 68 ( m , 2h ), 1 . 52 ( m , 1h ), 1 . 40 ( m , 2h ), 1 . 30 ( m , 2h ). esms m / z : 518 ( m + h ) + . in a round bottom flask 4 - chloro - phenyl isocyanate ( 100 mg , 0 . 65 mmol ) was dissolved in dcm ( 10 ml ) 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid , di - t - butyl ester ( 318 mg , 0 . 65 mmol ) was added and stirred for 3 hours . the reaction mixture was evaporated to dryness and the crude mixture was purified via flash column chromatography 2 : 1 hexanes / ethyl acetate to afford the tert - butyl ester as a white solid ( 470 mg , 96 %) which was deprotected using tfa / ch 2 cl 2 affording the desired product 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 5 ( s , 3h ), 8 . 35 ( s , 1h ), 7 . 40 ( dd , 2h ), 7 . 19 ( dd , 2h ), 6 . 30 ( t , 2h ), 6 . 10 ( t , 1h ), 4 . 08 ( m , 2h ), 3 . 05 ( m , 2h ), 2 . 32 ( m , 2h ), 1 . 90 ( m , 1h ), 1 . 68 ( m , 2h ), 1 . 52 ( m , 1h ), 1 . 40 ( m , 2h ), 1 . 30 ( m , 2h ). esms m / z : 474 ( m + h ) + . the same general procedure as shown in scheme a , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product ( 51 mg , 70 %) as an off - white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 9 ( br , 3h ), 7 . 95 ( m , 5h ), 7 . 6 ( m , 2h ), 6 . 35 ( br , 2h ), 4 . 1 ( m , 4h ), 2 . 9 ( br , 2h ), 2 . 55 ( m , 2h ), 2 . 25 ( m , 2h ), 1 . 70 ( m , 4h ), 1 . 3 ( m , 2h ). esms m / z : 460 ( m + h ) + . the same general procedure as shown in scheme 2 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product . esms m / z : 579 ( m + h ) + . the same general procedure as shown in scheme a , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods to yield the desired product ( 8 . 3 mg , 10 %) as an off - white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 7 . 8 ( d ), 7 . 3 ( d ), 6 . 3 ( dd ), 4 . 25 ( br ), 4 . 05 ( m ), 2 . 97 ( m ), 2 . 85 ( br ), 2 . 22 ( m ), 2 . 05 ( m ), 0 . 90 ( m ), 1 . 64 ( m ), 1 . 48 ( m ), 1 . 35 ( m ), 1 . 2 ( m ). esms m / z : 936 ( m + h ) + . the rhenium complexes of the saac - inhibitors are conveniently isolated from the reactions of the readily available precursor [ net 4 ] 2 -[ re ( co ) 3 br 3 ] with the saac - inhibitor . since the donor sets provided by the saac terminus are well documented as effective chelators for the { m ( co ) 3 } + 1 core and have been designed to adopt the required facial arrangement about the metal site , the preparations of the complexes were unexceptional . the { re ( i )( co ) 3 } + system followed similar reaction chemistry to that of the tc - 99m tricarbonyl core . the use of [ net 4 ] 2 [ rebr 3 ( co ) 3 ], as the starting material led to facile formation of the fac -{ re ( co ) 3 ( l ) 3 } core . the [ net 4 ] 2 [ rebr 3 ( co ) 3 ] was readily derived from the [ rebr ( co ) 5 ]. the synthesis of the re ( i ) complexes was accomplished by reacting [ net 4 ] 2 [ rebr 3 ( co ) 3 ] with the appropriate tec ligand in the ratio of 1 : 1 . 2 in 10 ml of methanol . the reaction was allowed to heat at 80 ° c . for 4 hours . after cooling all of the following reaction products were all purified using a small silica column with yields ranging from 10 - 30 %. ( mip - 1133 ). the peg2 dipyridyl compound , ( 17r , 21s )- 11 , 19 - dioxo - 1 -(□ yridine - 2 - yl )- 2 -(□ yridine - 2 - ylmethyl )- 5 , 8 - dioxa - 2 , 12 , 18 , 20 - tetraazatricosane - 17 , 21 , 23 - tricarboxylic acid was prepared employing the same general procedure as shown in scheme 1 , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the rhenium ester complex was prepared employing the same procedure as described in the general rhenium experimental . the compound was deprotected using the previously described methods to yield the desired product ( 2 mg , 20 %) as an off - white solid . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 8 ( d ), 8 . 00 ( dd ), 7 . 55 ( d ), 7 . 42 ( dd ), 6 . 45 ( s ), 3 . 95 ( m ), 3 . 4 - 3 . 6 ( m ), 2 . 45 ( m ), 1 . 25 ( m ), 1 . 1 ( m ), 0 . 8 ( m ). esms m / z : 931 ( m + h ) 4 . ( km11 - 200 ). the peg4 dipyridyl compound ( 23r , 27s )- 17 , 25 - dioxo - 1 -( pyridin - 2 - yl )- 2 -( pyridin - 2 - ylmethyl )- 5 , 8 , 11 , 14 - tetraoxa - 2 , 18 , 24 , 26 - tetraazanonacosane - 23 , 27 , 29 - tricarboxylic acid was prepared employing the same general procedure as shown in scheme a , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the rhenium ester complex was prepared employing the same procedure as described in the general rhenium experimental . the compound was deprotected using the previously described methods to yield the desired product . ( 5 . 1 mg , 29 . 6 %) as a white solid . esms m / z : 1019 ( m + h ) + . the peg8 dipyridyl compound , ( 35r , 39s )- 29 , 37 - dioxo - 1 -( pyridin - 2 - yl )- 2 -( pyridin - 2 - ylmethyl )- 5 , 8 , 11 , 14 , 17 , 20 , 23 , 26 - octaoxa - 2 , 30 , 36 , 38 - tetraazahentetracontane - 35 , 39 , 41 - tricarboxylic acid was prepared employing the same general procedure as shown in scheme a , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the rhenium ester complex was prepared employing the same procedure as described in the general rhenium experimental . the compound was deprotected using the previously described methods to yield the desired product ( 8 . 0 mg , 30 . 4 %) as a white solid . esms m / z : 1195 ( m + h ) + . the c11 - pama compound , ( 19r , 23s )- 13 , 21 - dioxo - 2 -(□ yridine - 2 - ylmethyl )- 2 , 14 , 20 , 22 - tetraazapentacosane - 1 , 19 , 23 , 25 - tetracarboxylic acid was prepared employing the same general procedure as shown in scheme a , using previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the rhenium ester complex was prepared employing the same procedure as described in the general rhenium experimental . the compound was deprotected using the previously described methods to yield the desired product ( 3 . 0 mg , 75 %) as an off - white solid . esms m / z : 922 ( m + h ) + . table 1 below is a summary of synthesized psma inhibitors investigated . β - amino acid analogs of mip - 1072 , mip - 1095 , mip - 1027 specifically but the extension to other analogs such as the technetium conjugates as well as other halogen analogs is very desirable . we have no new examples to support this claim at this time . the properties of the group vii metals technetium and rhenium are very similar due to their periodic relationship . it was anticipated that the metals would demonstrate similar reaction chemistry , which is often the case for the tricarbonyl , nitrogen , and thiazole chemistry of these two metals . likewise , due to their similar size that stabilizes the spin paired d 6 electron configuration of m ( i ), perrhenate and pertechnetate have very similar reaction behaviors . synthesizing the rhenium - tecs allowed us a facile route to structurally characterize the products . the periodic relationship between tc and re indicates that tc - 99m radiopharmaceuticals can be designed by modeling analogous rhenium complexes . some of the new compounds were synthesized with macroscopic quantities of rhenium for characterization by conventional methods , including mass - spectrometry , 1 h and 13 c nmr spectrometry . following purification , the synthesized rhenium complexes were run through a hplc column for purification and identification of retention times to compare with tc reaction products . the rhenium - tec complexes were also crystallized . the rhenium complexes of the saac - inhibitors are conveniently isolated from the reactions of the readily available precursors { re ( co ) 3 ( h 2 o ) 3 } + 1 and [ net 4 ] 2 [ re ( co ) 3 br 3 ] with the saac - inhibitor . since the donor sets provided by the saac terminus are well documented as effective chelators for the { m ( co ) 3 } + 1 core and have been designed to adopt the required facial arrangement about the metal site , the preparations of the complexes were unexceptional . the { re ( i )( co ) 3 } + system followed similar reaction chemistry to that of the tc - 99m tricarbonyl core . the use of [ net 4 ] 2 [ rebr 3 ( co ) 3 ], as the starting material led to facile formation of the fac -{ re ( co ) 3 ( l ) 3 } core . the [ net 4 ] 2 [ rebr 3 ( co ) 3 ] was readily derived from the [ rebr ( co ) 5 ]. the synthesis of the re ( i ) complexes was accomplished by reacting [ net 4 ] 2 [ rebr 3 ( co ) 3 ] with the appropriate tec ligand in the ratio of 1 : 1 . 2 in 10 ml of methanol . the reaction was allowed to heat at 80 ° c . for 4 hours . after cooling all of the following reaction products were all purified using a small silica column with yields ranging from 10 - 30 %. 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 65 ( dd , 2h ), 7 . 85 ( dd , 2h ), 7 . 7 ( dd , 4h ), 7 . 25 ( dd , 2h ), 6 . 42 ( dd , 1h ), 6 . 0 ( dd , 1h ), 4 . 5 ( m , 2h ), 4 . 16 ( m , 2h ), 3 . 80 ( m , 4h ), 2 . 45 ( m , 2h ), 2 . 0 ( dd , 2h ), 1 . 5 ( m , 4h ), 1 . 25 ( m , 6h ). esms m / z : 812 - 815 . ( mip 1029 ). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 12 . 6 ( s , 2h ), 8 . 91 ( s , 1h ), 8 . 63 ( dd , 2h ), 7 . 85 ( dd , 2h ), 7 . 75 ( dd , 4h ), 7 . 3 ( dd , 2h ), 6 . 44 ( d , h ), 6 . 28 ( d , 1h ), 4 . 45 ( s , 2h ), 4 . 10 ( m , 2h ), 3 . 15 ( s , 1h ), 2 . 60 ( m , 2h ), 2 . 25 ( m , 2h ), 1 . 90 ( m , 1h ), 1 . 78 ( m , 2h ), 1 . 45 ( m , 2h ). esms m / z : 770 - 774 . the same general procedure , using the previously prepared and protected 2 -[ 3 -( 5 - amino - 1 - carboxy - pentyl )- ureido ]- pentanedioic acid di t - butyl ester . the compound was deprotected using the previously described methods ( 2 . 2 mg , 65 %). 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 65 ( d , 1h ), 7 . 91 ( dd , 1h ), 7 . 56 ( d , 1h ), 7 . 45 ( dd , 1h ), 6 . 31 ( m , 2h ), 4 . 34 ( s , 2h ), 4 . 08 ( m , 4h ), 3 . 10 ( m , 2h ), 2 . 24 ( m , 2h ), 1 . 95 ( m , 1h ), 1 . 68 ( m , 4h ), 1 . 5 ( m , 1h ), 1 . 22 ( m , 2h ). esms m / z : 469 ( m + h ) + . m + 1 469 . 1 h nmr ( 400 mhz , dmso - d 6 ) δ 8 . 75 ( d , 1h ), 8 . 13 ( dd , 1h ), 7 . 69 ( d , 1h ), 7 . 57 ( dd , 1h ), 6 . 45 ( m , 2h ), 4 . 75 ( m , 1h ), 4 . 50 ( m , 1h ), 4 . 20 ( m , 2h ), 3 . 61 ( m , 4h ), 3 . 15 ( m , 2h ), 2 . 38 ( m , 1h ), 2 . 0 ( m , 2h ), 1 . 75 ( m , 4h ), 1 . 62 ( m , 1h ), 1 . 25 ( m , 2h ). esms m / z 779 - 782 ( m + 2na ) + . the compounds of the general structure 3 were prepared in overall yields ranging from 20 - 40 % using the general route depicted in scheme a . the key synthetic intermediate ( 1 ) was reacted with the appropriate aldehyde at room temperature in for one hour to form the □ yridi base intermediate . the □ yridi base was not isolated but was reduced in situ with sodium triacetoxyborohydride . the t - butyl ester protecting groups were removed using 50 % tfa in dcm for 1 hour at room temperature . upon completion of the deprotection , the reactions were concentrated on a rotary evaporator and purified by hplc or flash chromatography to afford the desired products ( 3 ) in 40 - 80 % yield . the following compounds of the general structure 8 were prepared in overall yields ranging from 20 - 60 % by the route depicted in scheme b . the key synthetic intermediate ( 4 ) was reacted with the appropriate phenylisocyanate at room temperature to afford the desired protected intermediates ( 5 ) in good yields . the t - butyl ester protecting groups were removed in the presence of 50 % tfa in dcm for 1 hour at room temperature . upon completion , the reactions were concentrated on a rotary evaporator purified by hplc or recrystallization to afford the desired products ( 6 ) in 40 - 90 % yield . preparation of the 99m tc - labeled complexes were achieved by addition of 100 μl of a solution containing [ 99m tc ( co ) 3 ( h 2 o ) 3 ] + to 500 μl of 10 − 4 m solutions of the inhibitor - saac . the mixtures were heated at 70 ° c . for 30 min . the products were analyzed for their radiochemical purity by reverse - phase hplc . the stability of the radiolabeled compounds in solution and in serum were determined as a function of time and solution conditions . specifically , after radiolabeling and isolation , the product was stored at room temperature for 6 h after which hplc analysis was performed to check for degree of label retention , as well as potential product degradation . the reformation of tco 4 − and the presence of the reduced material tco 2 was analyzed . to assist in predicting the in vivo stability , ligand challenges were performed . specifically , the stabilities of the 99m tc complexes were investigated by incubating the hplc purified complexes in 5 % mouse serum at room temperature and 37 ° c . the ability of competing ligands , such as cysteine and dtpa , to extract tc - 99m from the complexes was studied by incubating the purified complexes with solutions ( pbs ph 7 . 2 ) containing competing ligands at final concentrations of 0 . 1m . the results of the labeling competition studies demonstrated no degradation of the tc - 99m - complexes out to 6 hours in the serum or the competing ligands study . the results of the incubation at 37 ° c . after 6 hours are shown in fig2 . preparation of the iodine - 131 labeled compound n —[ n —[( s )- 1 , 3 - dicarboxypropyl ] carbamoyl ]- s - 3 - iodo - l - tyrosine ( i - 131 - dcit ) was achieved by addition of 100 ul of [ i - 131 ] nai in 0 . 1n naoh to a pbs ( ph 7 . 2 ) solution containing dct ( 1 mg / ml ) in an iodogen tube ™ ( fisher scientific , pierce ). the mixture was vortexed for 3 minutes and stored at room temperature for 20 minutes . the stability of the radiolabeled compound in solution was determined as a function of time . specifically , after radiolabeling and isolation , the product was stored at room temperature for 48 h after which hplc analysis was performed to check for degree of label retention , as well as potential product degradation . the reformation of nai and the presence of the reduced iodates was analyzed . the results of the labeling stability study demonstrated no significant degradation of the i - 131 dcit out to 2 days at room temperature . the results of the study are shown in fig3 . preparation of the iodine - 131 labeled compound 2 -{ 3 -[ 1 - carboxy - 5 -( 4 - iodo - benzoylamino )- pentyl ]- ureido }- pentanedioic acid ( i - 131 - mip 1072 ) was achieved by addition of 100 ul of [ i - 131 ] nai in 0 . 1n naoh with 30 μl methanol with 0 . 5 % acetic acid to a pbs ( ph 7 . 2 ) solution containing mip 1072 ( 1 mg / ml ) in an iodogen tube ( fisher scientific ). the mixture was vortexed for 3 minutes and stored at room temperature for 20 minutes . the stability of the radiolabeled compound in solution was determined as a function of time . specifically , after radiolabeling and isolation , the product was stored at 37 ° c . for 3 days after which hplc analysis was performed to check for degree of label retention , as well as potential product degradation . the reformation of nai and the presence of the reduced iodates was analyzed . the results of the labeling stability study demonstrated no significant degradation of the i - 131 1072 out to 3 days at room temperature in dmso , 10 % ethanol / saline , pbs ph 7 . 2 , and 6 % ascorbate / 3 % gentisic acid solution . the results of the study are shown in fig4 . the newly prepared saac - urea - glu conjugates were screened in a human prostate cancer cell binding assay using psma - positive , lncap cells , and psma - negative , pc3 cells . compounds demonstrating specific uptake or binding to psma - positive cells will be studied for tumor localization in vivo . in vitro cold screening assays verses i - 131 dcit . lncap and pc3 human prostate cancer cells were obtained from american type culture collection , rockville , md . lncap cells were maintained in rpmi - 1640 medium supplemented with 10 % fetal bovine serum ( fbs ). pc3 cells were grown in f12k medium supplemented with 10 % fbs . binding of the radiolabeled compound and competition with cold derivatives to lncap and pc - 3 cells was performed according to the methods of tang et al . ( tang , h . ; brown , m . ; ye , y . ; huang , g . ; zhang , y . ; wang , y . ; zhai , h . ; chen , x . ; shen , t . y . ; tenniswood , m ., prostate targeting ligands based on n - acetylated alpha - linked acidic dipeptidase , biochem . biophys . res . commun . 2003 , 307 , 8 - 14 ) with appropriate modifications . cells were plated in 12 - well plates at approximately 4 × 10 5 cells / well and incubated for 48 hours in a humidified incubator at 37 ° c ./ 5 % carbon dioxide prior to addition of compound . each unique saac - urea - glu conjugate was prepared and diluted in serum - free cell culture medium containing 0 . 5 % bovine serum albumin ( bsa ) in combination with 3 nm i - 131 dcit ( known inhibitor ). total binding was determined by incubating i - 131 dcit without test compound . plates were incubated at room temperature for 1 hour . cells were removed from the plates by gently pipeting and transferred to eppendorff tubes . samples were microcentrifuged for 15 seconds at 10k × g . the medium was aspirated and the pellet was washed twice by dispersal in fresh assay medium followed by microcentrifugation . cell binding of i - 131 dcit was determined by counting the cell pellet in an automated gamma counter . nonspecific binding was determined as the counts associated with the cells after incubating with 2 um nonradiolabeled compound or 2 - phosphonomethyl - pentanedioic acid ( pmpa ). the control compounds are depicted below . the two key compounds for the binding assays , are shown above : the i - dcit ( kozikowski et al ) and 2 - phosphonomethyl - pentanedioic acid ( pmpa — right ), a potent inhibitor with ic 50 = 6 nm . ( ii ) in vitro dose screening . i - 131 dcit bound specifically to lncap cells and not pc3 cells as is evident by the counts displaceable by nonradiolabeled compound or pmpa in lncap cells only ( fig5 ). binding constants were determined by incubating lncap cells with various amounts of nonradiolabeled dcit in the presence of a constant amount of i - 131 dcit and dividing by the specific activity of each solution to determine the number of fmoles compound bound ( fig6 ). the kd was determined to be 264 nm and bmax was 254 fmoles . compounds mip - 1008 and mip - 1033 which at 2 um competed with i - 131 dcit for binding to lncap cells , were retested at various doses to determine ic - 50 values ( fig7 and 8 ). while mip - 1072 , mip - 1095 , and mip - 1097 displayed ic50 values & lt ; 50 nm compounds mip - 1008 and mip - 1033 exhibited ic - 50s of 98 nm and 497 nm , respectively . compounds mip - 1025 , mip - 1028 , and mip - 1029 did not compete for binding ( table 1 ). in order to confirm the results of the scatchard analysis of fig7 indicating mip - 1072 internalization into lncap cells , the rate of uptake of mip - 1072 in lncap cells was monitored . each well was dosed with 100 nm mip - 1072 ( 2 uci / well ) at 4 ° c . and 37 ° c . binding to psma reached equilibrium after 15 min as evidenced by the plateau in the curve at 4 ° c . the cells incubated at 37 ° c . continued to internalize mip - 1072 after equilibrium had been reached . this result , fig1 , confirms the scatchard and indicates that mip - 1072 is indeed internalized . pooled male rat liver microsomes ( 1 mg / ml , bd biosciences ), nadph regenerating system ( 1 . 3 mm nadp , 3 . 3 mm glucose 6 - phosphate and 0 . 4 u / ml glucose 6 - phosphate dehydrogenase , bd biosciences ) and test compound ( 50 μm mip - 1072 , 50 μm dct , and 100 μm phenacetin ) were added to 0 . 1m potassium phosphate buffer ( ph 7 . 4 ) in order to monitor the catastrophic degradation of the test compounds . the mixture was incubated at 37 ° c . and at the indicated time ( 0 , 15 , 60 min ) the reaction was stopped by the addition of an equal volume of ice cold methanol ( 500 μl ). the resulting slurry was then centrifuged at 21 , 000 × g for 10 min and the supernatant was collected and injected onto an agilent lcms model msd sl using a 95 : 5 water : acetonitrile ( with 0 . 1 % formic acid ) to 40 : 60 water : acetonitrile ( with 0 . 1 % formic acid ) gradient and monitoring for the parent ion only in single ion mode . the results , shown in fig1 a and 11b , are expressed as degradation of the parent ion with respect to the 0 min time point . the stability of mip - 1072 was assessed using rat liver microsomes . mip - 1072 ( 50 μm ) and phenacetin ( 100 μm ) were incubated with rat liver microsomes at 37 ° c . for the indicated time . phenacetin was used as a control substance that is known to be metabolized . mip - 1072 was not degraded by the rat liver microsomes during the incubation period . however , phenacetin was degraded by 22 % after a 60 min incubation . the lead compound , mip 1072 , was i - 131 - labeled for tissue distribution studies in mice with both lncap ( psma positive ) and pc3 ( psma negative ) tumors implanted . the compound was radiolabeled by the route shown below . the tissue biodistribution results , were consistent with the in - vitro data , and demonstrated significant uptake in the lncap ( psma positive ) tumors . the results also displayed a high degree of specificity with very little activity in the pc3 ( psma negative ) tumors . a graph depicting the mice distribution is shown below ( fig1 ). the biological assessment using n —[ n —[( s )- 1 , 3 - dicarboxypropyl ] carbamoyl ]- s - 3 - iodo - l - tyrosine ( i - 131 - dcit ) verses “ cold ” complexes proved to be a rapid first screen , followed by dose curves to determine accurate ic 50 values . the lead series of compounds that exhibited ic50 values & lt ; 50 nm . in vivo data of the lead series demonstrated high affinity , with 3 % id / g accumulating in the lncap tumors , and high specificity with the lncap - to - pc3 ratio exceeding 15 - to 1 . wash cells off the plate by pipetting up and down with media . re - suspend cell pellet in 1 ml 50 mm tris - hcl , ph 7 . 4 , 0 . 5 % triton x - 100 since using detergent in lysis step , make working reagent , a ′ by adding 20 ul of reagent s to each 1 ml of reagent a that will be needed for the run . ( if a precipitate forms , warm and vortex ) combine 25 μl standard / unknown , 100 μl a ′, 800 μl reagent b in duplicate . mix after ˜ 15 min measure absorbance at 750 nm rxn buffer : 50 mm tris - hcl , ph 7 . 4 , 20 mm cocl2 , 32 mm nacl make cold naag ( 100 mm stock ) dilute 1 / 100 in rxn buffer for 1 mm combine 600 ul buffer and lncap cell lysate ( 200 μg ) pre - incubate 37 c for 3 min pre - incubate rxn buffer and lncap cell lysate for 3 min at 37 c add 6 μl of 1 mm naag ( for 1 μm final cone ) spiked with 1 , 000 , 000 cpm of 3 h - naag ( 100 μl of 1 mm naag + 10 μl of 3h - naag ( 10 / xi )). for competition add pmpa . at indicated time , stop reaction by removing 100 ul of the reaction - mix and adding an equal volume of ice cold 0 . 25 m kh 2 po 4 , ph 4 . 3 to stop the r × n apply ½ of mixture to 250 mg ag 50w - x4 cation exchange column ( 200 - 400 mesh , h + form , swell resin with di h2o prior to use ). save the other ½ for counting . wash column with 500 μl 1 : 1 rxn buffer / 0 . 25mkh 2 po 4 count 100 ul of the load , elution and reaction ( diluted 1 : 6 ) to minimize quenching notes : grant says inc only 10 min to ensure linearity , although luthi - carter , et al ( j pharm exp therap 1998 286 ( 2 )) says 2 hours still no effect on linearity and less than 20 % of the substrate consumed compounds of the present can be used to inhibit naaladase for therapeutic treatments . diseases that could be receptive to naaladase treatment include painful and sensory diabetic neuropathy , neuronal damage and prostate cancer , schizophrenia , colorectal cancer , inflammation , amyotrophic lateral schlerosis , or diabetic neuropathy . the present compounds can also be used an analgesic . guidance for the modeling of such therapeutic treatments can be found in goodman & amp ; gilman &# 39 ; s the pharmacological basis of therapeutics , mcgraw hill , 10 edition , 2001 , pharmaceutical preformulation and formulation : a practical guide from candidate drug selection to commercial dosage form , crc , 2001 and handbook of pharmaceutical excipients , apha publications , 5 edition , 2005 . the ability of non - radioactive analogs to compete with 131 i - dcit for binding to psma was tested in the psma positive human prostate cancer cell line , lncap cells . lncap cells ( 300 , 000 cells / well ) were incubated for 1 hour with 3 nm [ 131 i ]- dcit in the presence of 1 - 10 , 000 nm mip - 1072 in rpmi - 1640 medium supplemented with 0 . 5 % bovine serum albumin , then washed and counted in a gamma counter . all documents cited in this specification including patent applications are incorporated by reference in their entirety . the direct binding of 123 i - mip - 1072 to prostate cancer cells was examined ( fig1 ). lncap cells , or the psma negative cell line , pc3 cells , were incubated in rpmi - 1640 medium supplemented with 0 . 5 % bovine serum albumin for 1 hour with 3 nm 123 i - mip - 1072 alone , or in the presence of 10 μm unlabeled mip - 1072 , or 10 μm 2 -( phosphonomethyl )- pentanedioic acid ( pmpa ), a structurally unrelated naaladase inhibitor . cells were washed and counted in a gamma counter . the affinity constant ( iq ) of mip - 1072 was determined by saturation binding analysis ( fig1 ). lncap cells were incubated for 1 hour with 30 - 100 , 000 pm 131 i - mip - 1072 in hbs ( 50 mm hepes , ph 7 . 5 , 0 . 9 % sodium chloride ) at either 4 ° c . or 37 ° c . in the absence or presence of 10 μm unlabeled mip - 1072 ( to determine non - specific binding ). cells were then washed and the amount of radioactivity was measured on a gamma counter . specific binding was calculated as the difference between total binding and nonspecific binding . the affinity constant ( k d ) of the interaction of mip - 1072 with psma on lncap cells was determined by saturation binding analysis performed by titrating 123 i - mip - 1072 ( 3 pm - 1 , 000 nm ) in the presence and absence of an excess of non - radiolabeled mip - 1072 ( 10 μm ). a k d of 4 . 8 nm , and bmax of 1 , 490 fmoles / 10 6 cells at 4 ° c . was determined by nonlinear regression analysis using graph pad prism software ( fig1 ). the k d was not significantly different at 37 ° c ., 8 . 1 nm . the bmax , however , was greater at 37 ° c . than at 4 ° c . ; 1 , 490 vs . 4 , 400 fmol / 10 6 cells , respectively , indicating internalization of mip - 1072 . the results below are representative of two independent analyses . the ability of mip - 1072 to internalize in lncap cells was confirmed by an acid wash assay ( fig1 ). lncap cells were incubated in hbs with 100 nm 123 i - mip - 1072 for 0 - 2 hours at 4 and 37 ° c . at the indicated time the media was removed and the cells were incubated in mild acid buffer ( 50 mm glycine , 150 mm nacl , ph 3 . 0 ) at 4 ° c . for 5 minutes . after the brief incubation the cells were centrifuged at 20 , 000 × g for 5 minutes . the supernatant and cell pellet were counted in a gamma counter . in order to confirm the results of the saturation binding analysis indicating mip - 1072 internalization into lncap cells , we monitored the rate of uptake of mip - 1072 in lncap cells . each well was dosed with 100 nm mip - 1072 ( 2 uci / well ) at 4 ° c . and 37 ° c . binding to psma reached equilibrium after 15 min as evidenced by the plateau in the curve at 4 ° c . the cells incubated at 37 ° c . continued to internalize mip - 1072 after equilibrium had been reached . the results show a time dependent , acid insensitive increase in radioactivity associated with the pellet at 37 ° c . but not at 4 ° c ., indicating that 123 i - mip - 1072 is internalized at 37 ° c . but not at 4 ° c . ( fig1 ). a quantitative analysis of the tissue distribution of 123 i - mip - 1072 was performed in separate groups of male ncr nude −/− mice bearing psma positive lncap xenografts ( approximately 100 - 200 mm 3 ) administered via the tail vein as a bolus injection ( approximately 2 μci / mouse ) in a constant volume of 0 . 05 ml . the animals ( n = 5 / time point ) were euthanized by asphyxiation with carbon dioxide at 0 . 25 , 1 , 2 , 4 , 8 , and 24 hours post injection . tissues ( blood , heart , lungs , liver , spleen , kidneys , adrenals , stomach , large and small intestines ( with contents ), testes , skeletal muscle , bone , brain , adipose , and tumor ) were dissected , excised , weighed wet , transferred to plastic tubes and counted in an automated γ - counter ( lkb model 1282 , wallac oy , finland ). to compare uptake of 123 i - mip - 1072 in lncap versus pc3 tumors , and to demonstrate that the compound was on mechanism via competition with 2 -( phosphonomethyl )- pentanedioic acid ( pmpa ), some mice bearing either lncap or pc3 xenografts were pretreated with 50 mg / kg pmpa 5 minutes prior to injection with 123 i - mip - 1072 and selected tissues were harvested at 1 hour post injection . mip - 1072 , uptake and exposure was greatest in the kidney and lncap xenograft which express high levels of psma . peak uptake in the kidney was 158 ± 46 % id / g at 2 hours and the lncap xenograft was 17 ± 6 % id / g at 1 hours ( fig2 ). uptake in these target tissues was rapid , whereas the washout was slower in the lncap xenograft . 123 i - mip - 1072 was demonstrated to be on mechanism in vivo as evidenced by the localization to psma expressing lncap tumors but not pc3 tumors which do not express psma ( fig2 ). in addition , both the tumor and kidneys were blocked by pretreating the mice with pmpa , a potent inhibitor of psma .
compounds of formula wherein r is a c 6 - c 12 substituted or unsubstituted aryl , a c 6 - c 12 substituted or unsubstituted heteroaryl , a c 1 - c 6 substituted or unsubstituted alkyl or — nr ′ r ′, q is c , o , nr ′, s , s 2 , c 2 p y is c , o , nr ′, s , s 2 , c 2 p z is h or c 1 - c 4 alkyl , r ′ is h , c , s 2 , c 2 , a c 6 - c 12 substituted or unsubstituted aryl , a c 6 - c 12 substituted or unsubstituted heteroaryl or a c 1 - c 6 substituted or unsubstituted alkyl , when substituted , aryl , heteroaryl and alkyl are substituted with halogen , c 6 - c 12 heteroaryl , — nr ′ r ′ or cooz , which have diagnostic and therapeutic properties , such as the treatment and management of prostate cancer and other diseases related to naaladase inhibition . radiolabels can be incorporated into the structure through a variety of prosthetic groups attached at the x amino acid side chain via a carbon or hetero atom linkage .