thromboxane a 2 ( txa 2 ), which is derived from arachidonic acid via prostaglandin h 2 ( pgh 2 ), is implicated in several potentially noxious actions on various body systems , including platelet aggregation , bronchoconstriction and pulmonary and systemic vasoconstriction . thus txa 2 may be involved in the normal sealing of blood vessels following injury , but in addition may contribute to pathological intravascular clotting or thrombosis . furthermore , the constrictor actions of txa 2 on bronchiolar , pulmonary vascular and systemic vascular smooth muscle may be important in the development of several anaphyllactic conditions including bronchial asthma . furthermore , evidence exists that implicates txa 2 as well as pgh 2 in the pathogenesis of inflammation . it is an object of the present invention to provide a route of synthesis resulting in greater convenience , efficiency and yield of compounds having activity at thromboxane a 2 receptor sites , and most especially of those compounds having such activity which are inhibitors of thromboxane a 2 activity and are therefore of interest in one or more areas of medical treatment including the treatment of thrombotic disorders , the treatment of anaphylactic disease states , and treatments utilizing anti - inflammatory agents . this invention prepares compounds , by the following general method of scheme a , from (±) octahydro - 1α - methyl - 3aα , 7aα - 4α , 7α - methano - 2h - inden - 2 - one ( formula iii ), or derivatives thereof , which can be prepared by methods well known to those skilled in the art . ## str19 ## following the preparation of compound e by such well - known methods , the synthesis of the desired compounds preferably proceeds , for example , as follows in scheme b : ## str20 ## where the group r &# 39 ; is of the form --( ch 2 ) j --, it will be necessary to include a reduction step in order to convert the initially formed group r &# 39 ; having the formula -- ch 2 -- ch ═ ch --( ch 2 ) m --, where m is an integer equal to j - 3 , to the desired group --( ch 2 ) j --. this is done by reduction either of the intermediate of formula iv or , more preferably , the intermediate of formula v , by reaction with hydrogen in the presence of a suitable catalyst , such as palladium on charcoal . the preferred embodiments of this invention include intermediate compounds of the following general structure , used in the preparation of the corresponding thromboxane a 2 inhibiting bicycloheptenoic acid derivatives : ## str21 ## and the pharmaceutically acceptable salts thereof , wherein r 2 is as defined above . more specifically , the preferred embodiments include compounds of the above formula wherein r 2 is c 1 - 10 aliphatic hydrocarbon , and most especially preferred is the above compound wherein r 2 is methyl , namely (±) octahydro - 1α - methyl - 3aα , 7aα - 4α , 7α - methano - 2h - inden - 2 - one , ## str22 ## secondarily illustrative of the preferred embodiments of this invention include compounds of the following general structure , likewise used in the preparation of corresponding thromboxane a 2 inhibiting bicycloheptenoic acid derivatives : ## str23 ## and the pharmaceutically acceptable salts thereof , wherein r 2 is as defined above . more specifically , the preferred embodiments include compounds of the above formula wherein r 2 is c 1 - 10 aliphatic hydrocarbon , and most especially preferred is the above compound wherein r 2 is methyl , namely (±) octahydro - 1α - methyl - 4aα , 8aα ,- 5α , 8α - methano - 3h - 2 - benzopyran - 3 - one , ## str24 ## thirdly illustrative of preferred embodiments of this invention include compounds of the following general structure , likewise used in the preparation of corresponding thromboxane a 2 inhibiting bicycloheptenoic acid derivatives . ## str25 ## and the pharmaceutically acceptable salts thereof , wherein r 2 is as defined above . more specifically , the preferred embodiments include compounds of the above formula wherein r 2 is c 1 - 10 aliphatic hydrocarbon , and most especially preferred is the above compound wherein r 2 is methyl , namely (±) octahydro 1α - methyl - 4aα , 8aα ,- 5α , 8α - methano - 1h - 2 - benzopyran - 3 - ol , ## str26 ## fourthly illustrative of preferred embodiments of this invention include compounds of the following general structure , used in the preparation of corresponding thromboxane a 2 inhibiting bicycloheptenoic acid derivatives ## str27 ## and the pharmaceutically acceptable salts thereof , wherein r 1 and r 2 are as defined above . more specifically , the preferred embodiments include compounds of the above formula wherein r 1 is a group of the formula r &# 39 ;- coq where r &# 39 ; is --( ch 2 ) j -- where j is an independent integer of from 5 to 7 , especially 6 , or particularly where r &# 39 ; is -- ch 2 -- ch ═ ch --( ch 2 ) m where m is an independent integer of from 1 to 5 , especially 2 to 4 , and particularly 3 ; r 2 is c 1 - 10 aliphatic hydrocarbon , particularly methyl ; and coq is carboxy . other preferred embodiments are the above compound wherein coq is carboxy , m is 3 and r 2 is methyl , namely (±) 7 -[ 3β -( 1r *- hydroxyethyl )- 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl ]- 5z - heptenoic acid , ## str28 ## the following examples further illustrate details for the method of preparation of the invention and for compounds of the invention . the invention , which is set forth in the foregoing disclosure , is not to be construed or limited in spirit or in scope by these examples . those skilled in the art will readily understand that known variations of the conditions of the following preparative procedures can be used to prepare these compounds . all temperatures are degrees celsius unless otherwise noted . in these reactions , it is also possible to make use of variations which are in themselves known , but are not mentioned here in greater detail . the compounds of the invention are readily prepared according to one of the following reaction schemes , or modifications thereof , using readily available starting materials , reagents and conventional synthesis procedures . (±) 3aα , 4 , 7 , 7aα - tetrahydro - 4α , 7α - methano - 1h - indene , a . commercial dimer is suitable for use , if it has been protected from the air . a sample of a freshly opened aldrich ( aldrich chemical company , 940 west st . paul ave ., milwaukee , wis .) bottle showed only traces of impurities not present in a sample prepared by cracking the dimer and letting it dimerize over a period of weeks and then distilling under reduced pressure . the dimer is , however , susceptible to air oxidation . old bottles have solids present and upon cracking provide quantities of water and leave a large pot residue . (±) 3aα , 4 , 5 , 6 , 7 , 7aα - hexahydro - 4α , 7α - methano - 1h - indene , b . the hydrogenation over nickel boride , as described by brown et al ( brown , h . c . ; rothberg , i . ; vanderjagt , d . l ., j . org . chem . 1972 , 37 , 4098 - 4100 ) works quite well . other catalysts tried gave extensive overreduction . (±) octhydro - 3aα , 7aα - 4α , 7α - methano - 2h - inden - 2 - one , d . the hydroboration should be carried out in the manner described by brown , ibid . the bisulfite adduct is thick and hard to filter but it must be washed well with ether to remove all of the unsymmetrical ketone , (±) octahydro - 3aα , 7aα ,- 4α , 7α - methano - 1h - inden - 1 - one , c . (±) octahydro - 1α - methyl - 3aα , 7aα - 4α , 7α - methano - 2h - inden - 2 - one , e . to a solution of 6 . 9 ml ( 5 . 93 g , 41 . 9 mmole ) of n - isopropylcyclohexylamine in 20 ml of dry thf cooled in a - 78 ° bath was added 25 ml of 1 . 58 m n - butyllithium in hexane . after 15 min a solution of 5 . 62 g ( 37 . 5 mmole ) of d in 20 ml of thf was added over 20 min . after 15 min more , 5 ml ( 11 . 4 g , 80 mmole ) of methyl iodide was added quickly . ( alternatively , a methyl sulfonate can be used , such as methyl benzenesulfonate , methyl toluenesulfonate or methyl methanesulfonate .) after 30 min more , the mixture was allowed to warm to room temperature . after the addition of water ( 50 ml ) the mixture was extracted twice with ether . after washing with water and brine and then drying over sodium sulfate , the solvents were evaporated and the residue was chromatographed ( flash , hexane - etoac 99 : 1 ) to provide first 596 mq ( 9 %) of (±) octahydro - 1α , 3α - dimethyl - 3aα , 7aα - 4α , 7 . alpha .- methano - 2h - inden - 2 - one , f , followed by 3 . 81 g ( 62 %) of e , and then a small amount of crude d . in some runs the early part of the e fraction contained (±) octahydro - 1 , 1 - dimethyl - 3aα , 7aα - 4α , 7α - methano - 2h - inden - 2 - one , g . in a run which was allowed to stand at room temperature overnight before workup , a small amount of the isomeric (±) octahydro - 1α - methyl - 3aαβ , 7αβ - 4β , 7β - methano - 2h - inden - 2 - one , h , followed the main product closely . this isomer also forms under acidic equilibration . (±) octahydro - 1α - methyl - 4aα , 8aα ,- 5α , 8α - methano - 3h - 2 - benzopyran - 3 - one , i . to a solution of 3 . 81 g ( 23 . 2 mmole ) of e in 50 ml of dry methylene chloride was added 5 . 5 g ( 4 . 67 g , 27 mmole ) of 85 % m - chloroperoxybenzoic acid . after three days the solids were removed by filtration and rinsed with hexane . the filtrate was washed with sodium bicarbonate , water and brine . after evaporation of solvents chromatography ( flash , hexane - etoac 98 : 2 ) provided 47 mg e with aryl - containing byproduct . this was followed by 4 . 02 g ( 96 %) of i . crystallization from a small amount of hexane provides solid melting at 51 °- 52 . 5 °. (±) octahydro - 1α - methyl - 4aα , 8aα ,- 5α , 8α - methano - 1h - 2 - benzopyran - 3 - ol , j . a solution of 4 . 02 g ( 22 . 3 mmole ) of i in 5 ml of toluene was chilled in a - 78 ° bath and 30 ml of 1 m dibal in toluene was added and stirred at - 78 ° for 2 h . the mixture was quenched cautiously with 5 ml of meoh . after warming to room temperature , 50 ml more meoh was added . the solid was removed by filtration , rinsing thoroughly with meoh . the filtrate was evaporated , and the residue was crystallized from hexane to provide 3 . 23 g of j , mp 93 °- 94 °. chromatography of the mother liquors ( flash , 20 - 50 % etoac - hexane ) provided a small amount of crude i followed by a product fraction which was crystallized from hexane to provide an additional 0 . 33 g of j . total yield : 3 . 56 g ( 88 %). (±) 7 -[ 3β -( 1r *- hydroxyethyl )- 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2 . beta .- yl - 5z - heptenoic acid , k . to a suspension of 13 . 5 g ( 30 . 6 mmole ) freshly crushed and dried ( 60 °, high vac ) ( 4 - carboxybutyl ) triphenylphosphonium bromide in 75 ml dry thf was added 60 ml of a 1 m sodium ( bistrimethylsilyl ) amide in thf . the mixture was stirred at room temperature for 18 h under nitrogen and then a solution of 3 . 38 g ( 18 . 5 mmole ) of j in 50 ml of thf was added over 10 min . the temperature rose from 27 ° to 35 ° during the addition . during 1 h the color faded quickly and more white solids formed . after the addition of 100 ml of water the mixture was extracted with ether . the aqueous layer was acidified with 10 % hcl and extracted twice with ether washing with water and brine . after being dried over sodium sulfate the solvents were evaporated and the residue was chromatographed on a short acidic silica ( such as biosil a ® by bio - rad ) column with 20 % etoac - hexane to provide 4 . 90 g ( 99 %) of a crude product fraction consisting of about 90 % k and 10 % of the 5e isomer , (±) 7 - 3β -( 1s - hydroxyethyl )- 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2 . beta .- yl - 5e - heptenoic acid , l . traces of j could be recovered from the first ether extraction . (±) 7 -( 3β - acetyl - 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl )- 5z - heptenoic acid , m and (±) 7 -( 3α - acetyl - 1α , 4α - bicyclo [ 2 . 2 . 1 ]- hept - 2β - yl )- 5z - heptenoic acid , o . a solution of 4 . 90 g ( 18 . 4 mmole ) of crude k in 150 ml of acetone was chilled in an ice bath and titrated with jones reagent ( 5 . 5 ml ) until orange color persisted . the supernatant was decanted and concentrated to ca . 20 ml which was recombined with the solids and 100 ml of water . the mixture was extracted with ether . after washing with water and brine followed by drying over sodium sulfate the solvents were evaporated to leave 4 . 60 g of crude m with 10 % of the 5e isomer (±) 7 -( 3β - acetyl - 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl )- 5e - heptenoic acid , n which had partially isomerized to o and its 5e isomer (±) 7 -( 3α - acetyl - 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl - 5e - heptenoic acid , p . this material was dissolved in 50 ml of 1 n naoh and stirred at room temperature for 1 h . after acidification with 10 % hcl the product was extracted with ether which was washed with water and brine and dried over sodium sulfate . after evaporating solvents chromatography on a short acidic silica column ( 20 % etoac - hexane ) provided 4 . 38 g ( 90 %) of a mixture containing ca . 90 % o and 10 % p . no trace of m or n could be detected . (±) 7 -[ 3α -[[( phenylamino ) thioxomethyl ] hydrazonoethyl ]- 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl ]- 5z - heptenoic acid , sc - 44161 , and (±) 7 -[ 3α -[[( phenylamino ) thioxomethyl ] hydrazonoethyl ]- 1α , 4α - bicyclo [ 2 . 2 . 1 ] hept - 2β - yl ]- 5e - heptenoic acid , sc - 46986 . a solution of 1 . 20 g ( 4 . 5 mmole ) of the mixture of o and p in 5 ml of pyridine was stirred at room temperature for 22 h . a solution of the mixture in 100 ml of methylene chloride was washed twice with 100 ml 5 % hcl , water and brine . after drying over sodium sulfate and evaporation of solvent the residue was crystallized from 10 ml of ether to provide 1 . 364 g ( 73 %) of product , mp 129 °- 132 °. while the invention has been described and illustrated with reference to certain prepared embodiments and certain illustrative steps , those skilled in the art will appreciate that various changes , modifications and substitutions can be made therein without departing from the spirit and scope of the invention . it is intended therefore that the invention be limited only by the scope of the claims which follow , and that such claims be interpreted as broadly as is reasonable .