one particularly useful compound is the n - butylcarbamate derivative ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol ( sdl 11349 ) having the structure : the ic 50 for acetylcholinesterase inhibition for sdl 11349 is 10 . 9 × 10 − 7 m as compared to 3 . 97 × 10 − 7 m for galantamine . this compound was first described in han et al as a cholinesterase inhibitor in bioorg . & amp ; medicinal chemistry letters 1 , 11 579 - 580 ( 1991 ). the pathways by which galantamine cleared aβ , and protected neurons against aβ , glutamate and serca inhibition toxicity , can be activated by analogs which preserve the nicotinic positive allosteric modulatory properties of the molecule , while markedly reducing cholinesterase inhibition . galantamine butylcarbarnate has about 36 % of the enzymatic activity of galantamine . primary cultured rat neurons can be depolarized by the application of 1 . 5 mm choline . ( popa et al , j mol netirosci 2006 , 30 , 27 ). this is mediated by α 7 nicotinic receptors , as it could be blocked by methyllyaconitine and α - bungarotoxin , galantamine n - butylcarbamate , 1 μm , enhanced the depolarization caused by choline ( 15 . 9 ± 2 . 1 %). this was not significantly different from the effect of galantamine at the same concentration ( 20 . 6 ± 4 . 2 %). the enhancement produced by the n - butylcarbamate was blocked by the antibody to the galantamine recognition site on nicotinic receptors , fk - 1 , indicating that it was mediated by the galantamine positive allosteric modulatory site . galantamine n - butylcarbamate is thus a positive allosteric modulator at the galantamine site , with an effect similar to that of galantamine . the butylcarbamate differed from galantamine in adverse effects . ( han et al , eur j med chem 1992 , 27 , 673 ) decreased motility which appeared at 5 mg / kg in galantamine - treated animals was not observed up to 30 mg / kg of the analog . at doses of 50 - 100 mg / kg of the n - butylcarbamate , mice were wobbly and off - balance with rapid heart rate still present at 4 hours , but were recovered at 24 hours . there was no lethality up to 100 mg / kg . the ld50 of galantamine is 10 mg / kg . mice injected ip with 10 , 15 and 20 mg / kg galantamine develop seizures at an average of 8 , 6 and 4 minutes respectively . ( fonck et al , j neurosci 2003 , 3 , 7 , 2582 ) galantamine n - butylcarbarmate is predicted to have 80 % oral bioavailability , based on in vitro permeability of a layer of caco - 2 cells , derived from a human colorectal carcinoma , as shown below . in an in - vitro preparation of liver microsomes , the half - life of galantamine n - butylcarbamate was greater than 60 minutes . as shown below , this suggests that the compound is not metabolized to a substantial degree in the liver . galantamine n - butylcarbamate is stable for greater than two hours in mouse plasma . concentrations at two hours are slightly lower than those of galantamine which has a plasma half - life of about 7 hours in human patients . the mouse plasma data are shown in fig3 and 4 . the pharmacokinetic data were produced by apredica , 313 pleasant st , watertown mass . 02472 . mice with lesions of the nucleus basalis magnocellularis ( nbm ) have poor memory for the fact that if they cross from a lighted compartment into a dark one , which they prefer , they will receive a shock through the floor grid . when given galantamine n - butylcarbamate during training , mice will remain in the lighted compartment about 100 seconds longer than when given saline . ( han et al , 1992 , op cit ) as shown in fig5 , the best dose for this memory enhancement is 0 . 5 mg / kg . a similar effect is seen with galantamine . however , optimal performance is an increase of about 125 seconds , and the best dose is 3 mg / kg , 6 × that of the n - butylcarbamate . in summary , sdl 11349 based on animal and in - vitro studies , appears to be well tolerated , safe , orally bioavailable , stable in plasma , and effective in enhancing learning at lower doses than galantamine . it enhances neuronal electrophysiological activity via the galantamine positive allosteric modulatory site on nicotinic receptors . it substantially enhances the clearance of toxic aβ42 oligomers by microglial cells , to a degree greater than the clearance deficit identified in late onset ad patients ( fig6 ). furthermore , it can prevent aβ42 oligomer - induced loss of dendrites , a characteristic finding in the alzheimer brain , a protective effect comparable to that of the “ gold standard ”, bdnf ( brain - derived neurotrophic factor ), ( fig7 ) this is easily appreciated from the photomicrographs ( fig8 ). dendritic spines are decreased in the alzheimer brain ( gruntzendler et al , op cit ). these spines , particularly mature ones with more frequent large heads , are significantly increased by sub - chronic sdl 11349 treatment in young adult mice in the stratum radiatum of cal this area is affected early in ad and its width correlates with cognitive functions . ( kerchner g a et al , neuroimage 2012 , 63 ( 1 ), 194 - 202 ) ( fig9 - 11 ) thus , sdl 11349 increases clearance of ab42 oligomers to a substantial extent , while protecting against the toxicity of remaining oligomers , and has trophic effects in one of the earliest affected areas in ad . the present invention utilizes concentrations in brain of from about 0 . 05 - 1 . 8 μm , more commonly 0 . 2 to 1 . 5 μm for example about 0 . 5 - 1 . 0 μm of an analog of ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol . determination of suitable dose ranges for individual compounds can be effected by assessing the concentration of the analog which promotes aβ oligomer clearance in vitro , and to temper that with the concentration which preserves the neurite network from injury by remaining oligomers . the analog is then administered to experimental animals to determine plasma and brain concentrations , and the plasma concentration which is associated with an effective brain concentration is applied to human subjects . several concentrations will typically be tried in human subjects , with measurement of aβ species in brain or aβ42 in csf , and clinical outcomes . compositions suitable for use in treatments according to the invention are typically suitable for oral administration such as tablets , capsules , or lozenges containing from 0 . 1 to 40 mg , of the active compound depending upon the activity and half - life of the compound . compositions using sdl 11349 will typically contain , for example , in the range 0 . 5 to 10 mg , or 1 to 8 mg per dose . oral dosage forms may be sustained dosage formulations in which the particles of the active compound are coated so as to delay release into the blood stream for example by coating with a pharmaceutically acceptable polymer that is dissolved in gastric juices such as polyvinyl pyrrolidone and then sizing the particles and incorporating specific ratios of particles of particular sizes into a tablet , capsule or lozenge so that particles having different degrees of thickness of coating are released at different times , or using a controlled - release device which employs osmosis , for example . in the present case , the coating or delayed technique will desirably result in most of the active compound being released within twelve hours of administration . alternative means of application may include for example transdermal patches in which case the objective is to provide administration of a dosage at a rate of 0 . 01 to 10 mg per hour . other dosage forms may be used if desired . for example nasal or parenteral , including dosage formulations to assist passage of the blood - brain barrier . for the purpose of nasal or parenteral therapeutic administration , the active compounds of the invention may be incorporated into a solution or suspension . these preparations typically contain at least 0 . 1 % of active compound , for example between 0 . 5 and about 30 % of the weight of the solution or suspension . preferred compositions and preparations according to the present inventions are prepared so that a nasal or parenteral dosage unit contains between 0 . 1 to 10 milligrams of active compound . the solutions or suspensions may also include the following components : a sterile diluent such as water for injection , saline solution , fixed oils , polyethylene glycols , glycerine , propylene glycol or other synthetic solvents ; antibacterial agents , such as benzyl alcohol or methyl parabens ; antioxidants such as ascorbic acid or sodium bisulfite ; chelating agents such as ethylene - diamine tetraacetic acid ; buffers such as acetates ; citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose . parenteral multiple dose vials may be of glass or plastic . typical dosage rates in administration of the active ingredients depend on the nature of the compound that is used and in intravenous administration are in the range of 0 . 01 to 2 . 0 mg per day and per kilogram of body weight based on the physical condition and other medications of the patient . liquid formulations for nasal or intra - cerebroventricular administration at a concentration of 0 . 1 to 5 mg of active ingredient / mi . the compounds according to the invention can also be administered by a transdermal system , in which 0 . 1 to 10 mg / day is released . a transdermal dosage system may consist of a storage layer that contains 0 . 1 to 30 mg of the active substance as a free base or salt , in case together with a penetration accelerator , e . g ., dimethyl sulfoxide , or a carboxylic acid , e . g ., octanoic acid , and a polyacrylate , e . g ., hexylacrylate / vinyl acetate / acrylic acid copolymer including softeners , e . g ., isopropylmyristate . as a covering , an active ingredient - impermeable outside layer , e . g ., a metal - coated , siliconized polyethylene patch with a thickness of , for example , 0 . 35 mm , can be used . to produce an adhesive layer , e . g ., a dimethylamino - methacrylate / methacrylate copolymer in an organic solvent can be used . the determination of a particular dose for any given patient will be a matter for the judgment of the physician treating the patient . however , when using sdl11349 , these will be in the range of from 1 . 0 to 10 mg or 2 to 8 mg per day to achieve a concentration in brain in the range 0 . 4 - 1 . 2 μm . some compounds of use in the present invention are acetyl cholinesterase inhibitors . for some users of these drugs , inhibition of acetylcholinesterase may lead to excess mental activity during periods of intended sleep and lead to insomnia . for such persons , a dosage regime should be chosen to avoid significant levels of active compounds in the brain during periods of intended sleep . the half - life of the compounds of the present invention in the body is typically less than 12 hours and may be as low as six hours . avoidance of significant concentrations of active compound during periods of intended sleep can therefore be achieved by avoiding taking drug in the evening , for example taking a daily dose divided into two , three or four units to be taken throughout the day , typically to be taken at meal times . alternatively a delayed or sustained drug release formulation may be used . for other users , sleep disorders may not be a problem and there may be benefit in maintaining levels of ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol analogs during sleep to assist in clearance of β - amyloid species from brain through the glymphatic system . for an individual patient , suitable dosages may be determined by starting with a low daily dose such as 0 . 1 mg , or 1 to 2 mg , and increasing if there is insufficient response . the amounts of active compounds required by the present invention are those that will promote removal of or retard accumulation of aβ deposits in cortex while reducing the lowering of csf aβ42 . depending on the relative efficacy of the compound as a cholinesterase inhibitor and a nicotinic stimulator , this may be lower than the dose required to treat dementia associated with alzheimer &# 39 ; s disease where acetylcholinesterase inhibition is an important requirement . this property is not a desirable factor in choosing a dose for the present invention . treatments according to the first and second embodiments of the invention require a determination of levels of aβ 1 - 42 or aβ x - 42 monomer , referred to as aβ42 , in the csf , or measures reflecting β - amyloid deposits in cortex . this can be effected by standard methods such as lumbar puncture and pet scanning with ligands for β - amyloid such as pittsburgh compound b ( pib ), amyvid ( florbetapir ), visamyl ( flumetamol ), neuroseq ( florbetaben ) 18 f - nav4694 or others which may be developed . the determination of the levels of csf aβ42 at which treatment should be commenced will depend upon a variety of factors such as age , education , apoe4 status , diabetes , genes which cause ad and others . the cutoff for aβ42 concentration is based on csf aβ42 concentrations in csf indicating aβ deposition in brain , and a similar value separating healthy elderly from alzheimer &# 39 ; s disease patients . ( weigand et al , op cit ; de meyer et al , op cit ) typically , however , treatment will be commenced if csf aβ42 levels fall below 225 pg / ml , for example , below 192 pg / ml as determined using the inno - bia alzbio3 test kit luminex assay or 450 - 650 pg / ml , using the innotest β - amyloid ( 1 - 42 ) elisa assay , depending on the pet tracer and cortical and reference regions , or have been dropping by more than 1 % per year , 10 % since the baseline measurement , or have fallen on two consecutive post - baseline measurements , with at least 3 month intervals . a summary of currently available csf aβ42 levels corresponding the cortical aβ deposition is available in blennow et al , trends in pharmacological sciences , 2015 , 36 , 5 , 297 , table 2 . standardization efforts within the alzheimer research community are underway for this measurement . treatment according to the third embodiment of the invention may involve volumetric mri scanning or determination of fluorodeoxyglucose uptake by pet scanning , as noted by sperling et al ., op cit 2011 . treatment according to the sixth embodiment of the invention involves administration of nicotine agonists such as evp 6124 , dmxb - a , azd 1446 , abt 894 , or others mentioned above together with one of ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol &# 39 ; s analogs as specified above . the agonists assist in clearance of aβ from plaque and so establishment of useful levels where required is by beginning low and increasing the dose until a response is seen in pet scanning for amyloid , or csf aβ consisting of a slower progression of abnormality . the combination of a ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol analog and a nicotinic agonist may cause cardiac side effects and extreme caution should be used with this combination . typically the daily dose of ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol analog and agonists will be will be 0 . 1 to 100 mg , preferably 1 - 50 mg , or 2 - 10 mg , or 10 - 30 mg for example , given in a single dose , divided doses or a controlled release formulation . the daily dose can also be calculated based on weight , such as 0 . 001 to 0 . 15 mg / kg or 0 . 01 to 0 . 1 mg / kg and 0 . 5 to 50 mg for the agonists . the actual dosages of each will be determined by following amyloid levels in brain and aβ42 in csf and will typically be in the range of 0 . 2 mg to 100 mg for a ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol analog , preferably 2 - 10 mg , or 1 - 50 mg and from 0 . 5 mg to 50 mg for the agonist , preferably 2 - 30 mg . treatment according to the seventh embodiment of the invention requires determination of whether a patient has the apoe4 isoform of apolipoprotein e . this may be done by genetic testing . if a patient is found to fall into this category , suitable dosage levels may be determined in the same manner as for the first and second embodiments . treatment according to the eighth embodiment , down &# 39 ; s syndrome , would follow the guidelines of amyloid deposition as described with respect to the sixth embodiment and csf aβ42 as described with respect to the first and second embodiments . ( 4as , 6r , 8as )- 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah -[ 1 ] benzofuro [ 3a , 3 , 2 - ef ][ 2 ] benzazepin - 6 - ol and its analogs for use according to the present invention share the same contraindications as other cholinergic drugs . thus care should be taken before using the present invention on pre - pubertal children and patients who suffer for example from asthma , epilepsy , bradycardia , heart block , hemorrhagic ulcer disease . furthermore , animal studies have shown that cholinergic drugs may result in overstimulation of the uterus and ovaries in premenopausal women . abeta oligomers were prepared using beta - amyioid ( 1 - 42 ) from american peptide ( product # 62 - 0 - 80 ). one aliquot was dissolved in an adequate volume of tbs ( 50 mm tris - buffer , 150 mm nacl , ph = 7 . 4 ) to achieve a final concentration of 1 . 7 mg / ml ( corresponding to 340 μm ). the solution was sonicated for 2 minutes and then diluted 1 : 2 in water to obtain a final concentration of 170 μm . next , the abeta was allowed to aggregate at 4 ′ c for 48 hours . prior to application , the solution was sonicated for another minute . bv - 2 microglial cells were kept in culture medium ( dmem medium , 10 % fbs , 2 mm glutamine , 1 % penc / strep ) until 80 - 90 % confluency . cells were maintained at 37 ° c ., 95 % humidity and 5 % co 2 . afterwards , cells were seeded in culture medium on 24 - well plates at a cell density of 1 × 10 5 cells per well . after 24 h , the medium was exchanged for the treatment medium ( dmem medium , 5 % fbs , 2 mm glutamine ). cells were treated with different concentrations of sdl 11349 as depicted in fig6 for 24 h before oligomer application . oligomerized aβ1 - 42 ( 10 μm ) was applied to the cells for 6 h . afterwards the cell supernatant ( medium ) was collected . the medium was separated by affinity ( removing monomers ) and the oligomers not phagocytosed were disaggregated by hfip treatment and measured by msd . ( msd ® 96 - well multi - spot ® 6e10 abeta triplex assay ( mesoscale discovery ) the immune assay was carried out according to the manual and plates were read on the sector imager ( msd ). analyte levels were evaluated according to adequate aβ peptide standards ( msd ). experiments were carried out in nine ( fig6 ) replicates . data are presented as mean ± standard error of mean ( sem ). group differences are evaluated by one - way anova . sdl 11349 applied for 24 hours reduced the β - amyloid oligomer concentration in the medium significantly , by approximately 38 - 40 % over a concentration range of 0 . 11 to 0 . 67 μm . the anova was significant at p = 0 . 009 . this experiment was performed by qps austria , parkring 12 , a - 8074 grambach , austria . rat cortical neurons were cultured as described by callizot et al ( j neurosci res 2013 , 91 : 706 - 716 ). on day 11 of culture , aβ oligomer solution , 20 μm , was applied . the aβ oligomer preparation , having an average weight of 90 kda , prepared as described by callizot et al ( op cit ) contained only diffusible species , not fibrils or protofibrils . briefly , aβ1 - 42 peptide at a concentration of 40 μm was dissolved in the culture medium , gently agitated for 3 days at 37 ° c . in the dark , and used immediately after dilution . sdl 11349 and bdnf ( 50 ng / ml ) were dissolved in culture medium ( maximum of 0 . 1 % dmso final concentration ) then pre - incubated with primary cortical neurons for 24 h before the aβ1 - 42 oligomer solution application . the oligomers were incubated with the neurons and various concentrations of sdl 11349 , or bdnf , 50 ng / ml , the positive control , for 24 hours , in 6 replicates per condition . then the supernatant was removed and the neurons were fixed with a cold ethanol and acetic acid solution . the cells were permeabilized with 0 . 1 % saponin and then incubated for 2 h with mouse monoclonal antibody and microtubule - associated protein 2 ( map - 2 ). subsequently , alexa - fluor 488 goat anti - mouse igg was applied , and images were obtained and analyzed automatically . the neurite network was reduced by 40 % by the aβ oligomer preparation . sdl 11349 , at 1 μm , blocked the toxic effect of the aβ oligomers , comparably to the protective effect of the positive control , bdnf , as shown in fig7 . significant beneficial effects were seen from 0 . 66 to 4 . 0 μm sdl 11349 . data are presented as mean ± standard error of the mean . asterisks indicate * p & lt ; 0 . 05 , one way anova followed by plsd fisher &# 39 ; s test . the effect of sdl 1 μm , can be appreciated in fig8 . the normal neurite network , as shown in fig8 ( a ), becomes sparse when treated with aβ oligomers as seen in 8 ( b ), bdnf , the “ gold standard ” for this assay , preserves the neurite network , panel ( c ), and sdl 11349 produces a result which is comparable to bdnf , panel 8 ( d ), and to the control well , panel 8 ( a ). this work was performed at neuro - sys , 410 cd 60 , parc de l &# 39 ; oratoire de bouc , f - 13120 , gardanne , france dendritic spines are fundamental to cognitive processes and are decreased in areas of fibrillar amyloid deposits in the alzheimer brain . ( gruntzendler et al , op cit ) adult c57b16 mice , ( 8 weeks old ) were administered vehicle or sdl 11349 , 0 . 005 , 0 . 03 , 0 . 07 , 0 . 1 or 0 . 2 mg / kg , ip , per day for five days prior to sacrifice after rapid anesthetization with isofluorane . brain tissue was sectioned into 300 μm slices from anterior to posterior extremes . ballistic dye labelling was performed , followed by laser - scanning confocal microscopy ( olympus fv1000 ) using a 63 × objective ( 1 . 42 na ) to scan individually labelled neurons at high resolution ( 0 . 103 × 0 . 103 × 0 . 33 μm voxels ). target neurons were identified in the brain region of interest by anatomical location and cell morphology . microscopy was performed blind to experimental conditions . a minimum of 5 samples per animal were measured for each segment . blind deconvolution ( autoquant ) was applied to raw three - dimensional digital images which were then analyzed for spine density and morphology by trained analysts . individual spines were measured manually for ( a ) head diameter , ( b ) length , and ( c ) neck thickness from image z - stacks using custom - built afraxis esp software . each dendrite was analyzed by 3 independent analysts . automated image assignment software ( c ++) distributed images to analysts in a randomized manner and ensured that each analyst performed measurements of near equal numbers of dendrites per group . analysts were blinded to all experimental conditions . statistical analysis of interanalyst variability for each dendrite was examined online and used to eliminate dendrites that did not meet interanalyst reliability criteria : a dendrite was incorporated into the final analysis only if measurement distributions for all three measures failed to be significantly different between analysts . for spine density and spine morphological classification , data across analysts were averaged to report data for each dendrite . data population values ( n &# 39 ; s ) were reported from dendrites collected equally from all mice . values are reported in tables and plots as group means ± standard errors of the mean ( sems ). for all group comparisons of parametric values , statistical significance was determined using the analysis of variance test ( anova ; spss ). post - hoc comparisons were assessed using the student &# 39 ; s t - test ( 2 tails ). all afraxis experimenters were fully blinded to treatment conditions during the collection , assembly and interpretation of the data . non - parametric comparisons of individual measure population distributions were conducted using the 2 - sample kolmogorov - smirnov test α =. 0001 ). dendritic spine morphology was analyzed from samples taken from secondary apical dendrites , and secondary basal dendrites of ca1 pyramidal neurons in the dorsal hippocampus . a representative laser - scanning confocal micrograph is shown in fig9 , showing a sampled position . from each animal , three sections were collected ( derived between − 1 . 4 and − 2 . 9 mm from bregma ) and five individually labelled neurons identified . a 50 μm segment was analyzed from each location . total spine density values for each group are described in fig1 . all treatment groups expressed a statistically significant difference ( p & lt ; 0 . 05 , 2 - tailed t - test ) or trend ( p & lt ;. 01 ) compared to vehicle controls in apical dendritic samples . there was no effect in basal samples . the magnitude of effect and reliability across all dose levels for sdl 11349 treatment is striking . based on the magnitude of effect versus control , there does not appear to be a dose - dependent modification of spines by sdl 11349 within the range tested here . dendritic spine maturity categories are described in fig1 and shown in fig1 and 11 . raw dendritic spine morphometric values ( spine length , head diameter , neck width ) are assembled into a 12 - category classification scheme that describes highly granulated dendritic spine phenotypes . these categories are collapsed to represent immature , intermediate and mature scores . finally , an assessment independent from the 12 - point scheme is used to describe classic spine phenotypes ( e . g . mushroom stubby , etc .). the total spine density effect in apical dendritic samples was largely driven by changes to mature spine phenotypes . ai treatment groups expressed significantly increased mature spine densities versus vehicle controls . this translated into generalized increases in stubby and mushroom spines . this work was performed by afraxis , 6605 nancy ridge drive , suite 224 , san diego , calif . 92121 .
analogs of - 5 , 6 , 9 , 10 , 11 , 12 - hexahydro - 3 - methoxy - 11 - methyl - 4ah - benzofurobenzazepin - 6 - ol of the formula : wherein r 1 carbamate , carbonate or carboxlate group ; r 2 is alkoxy group of from one to six carbon atoms , a hydroxy group , hydrogen , an alkanoyloxy group or 2 to 10 carbon atoms , a benzoyloxy or substituted benzoyloxy group , a carbonate group of 1 to 10 carbon atoms or a carbamate group such as a mono alkyl or dialkyl or an aryl carbamate wherein the alkyl groups or aryl groups contain from 1 to 10 carbons ; and r 3 is hydrogen , alkyl of 1 to 10 carbon atoms , benzyl , cyclopropylmethyl group or a substituted or unsubstituted benzoyloxy group are of use in treating persons meeting criteria for having a risk of developing alzheimer &# 39 ; s type dementia , before symptoms of dementia are observed by reducing the decline of aβ amyloid csf .