共查询到18条相似文献,搜索用时 171 毫秒
1.
2.
3.
4.
5.
6.
7.
碱性拆分剂的选择不象酸性拆分剂的选择那么有限,但在众多合成的碱性拆分剂中,既廉价易得,而又有高拆分效果的物质很少。最常用的α-苯乙胺,由于其水溶性,有时会使拆分遇到困难。我们将光活性α-对氯苯基异戊酸[S(+)Ⅰ,R(-)Ⅰ]和它的降解产物α-异丙基对氯苄胺[S(-)Ⅱ,R(+)Ⅱ]分别用于拆分(±)1-苯基-2-对甲苯基乙胺(PTE)、(±)α-苯乙 相似文献
8.
9.
10.
以光学活性(R)-α-苯乙胺(1)为拆分剂,将cis,cis-3-N-叔丁氧羰基氨基-5-甲氧羰基环己基甲酸[(±)-2]拆分为cis,cis-(-)-2,其结构经1H NMR和13C NMR确证。最佳拆分条件为:以丙酮为溶剂,n(1)∶n[(±)-2]=1.0∶1.0,拆分效率34.1%。 相似文献
11.
利用非对映异构体盐在溶剂中溶解度的不同,以(1S,2R)-1-氨基-2-茚醇(1)为手性拆分剂,拆分四氢糠酸[(RS)-THFA, (RS)-2]获得高光学纯的(S)-2,其结构经1H NMR, 13C NMR和HPLC确证。探究了不同溶剂量和投料比对拆分效果的影响。结果表明较佳拆分条件为:以4-甲基-2-戊酮(3)作溶剂,n[(RS)-2]: n(1)=2.2 : 1,一次拆分得91.7% ee (S)-2;再以n[91.7% ee (S)-2]: n(1)=6 : 5进行二次拆分得99.0% ee (S)-2。拆分剂的回收率提高至92.0%,同时对拆分母液中的非目标对映体成功地进行消旋化,回收率为89.0%,实现了四氢糠酸的循环拆分。 相似文献
12.
Cvetovich RJ Chartrain M Hartner FW Roberge C Amato JS Grabowski EJ 《The Journal of organic chemistry》1996,61(19):6575-6580
A convergent synthesis of [S-(R,S)]-2-[4-[(4-methylpiperazin-1-yl)carbonyl]phenoxy]-3,3-diethyl-N-[1-[3,4-(methylenedioxy)phenyl]butyl]-4-oxo-1-azetidinecarboxamide (L-694,458, 1), a potent human leukocyte elastase inhibitor, was achieved via chiral synthesis of key intermediates: (S)-3,3-diethyl-4-[4'-[(N-methylpiperazin-1-yl)carbonylphenoxy]-2-azetidinone (2) and (R)-alpha-propylpiperonyl isocyanate (3). Synthesis of beta-lactam 2 was achieved by a novel enantioselective lipase hydrolysis of ester 5 to produce (S)-3,3-diethyl-4-(4'-carboxyphenoxy)-2-azetidinone (6) (60% yield, three cycles, 93% ee) with isolation, epimerization, and recycling of the undesired (R)-ester 5. Isocyanate 3 was prepared by chiral addition of Zn(n-Pr)(2) to piperonal (98% yield, 99.2% ee), azide displacement and reduction to (R)-alpha-propylpiperonylamine (11) (58% yield, 85% ee), crystallization as the D-pyroglutamic acid salt (92% yield, 98.2% ee), and isocyanate formation (98% yield) with phosgene. 相似文献
13.
Shiraiwa T Suzuki M Sakai Y Nagasawa H Takatani K Noshi D Yamanashi K 《Chemical & pharmaceutical bulletin》2002,50(10):1362-1366
To synthesize optically active 2-amino-2-methyl-3-phenylpropanoic acid (1), (RS)-2-benzoylamino-2-benzyl-3-hydroxypropanoic acid [(RS)-2] was first optically resolved using cinchonidine as a resolving agent to yield optically pure (S)- and (R)-2 in yields of about 70%, based on half of the starting amount of (RS)-2. Next, the racemic structure of (RS)-2 was examined based on melting point, solubility, IR spectrum, and binary and ternary phase diagrams, with the aim of optical resolution by preferential crystallization of (RS)-2. Results indicated that the (RS)-2 exists as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization yielded (S)- and (R)-2 with optical purities of about 90%, which were fully purified by recrystallization. After O-tosylation of (S)- and (R)-2, reduction by zinc powder and sodium iodide gave (R)- and (S)-1, respectively. 相似文献
14.
酰胺型手性固定相反相拆分布洛芬药物对映体 总被引:5,自引:0,他引:5
利用酰胺型手性固定相反相拆分了布洛芬对映异构体,用有0.01mol/L NH4Ac的甲醇和水作流动相。在优化分离条件的同时,研究了不同的有机调节和对分离的影响,并探讨了分离的机理。 相似文献
15.
The racemic structure of (1RS,3RS)-1,2,3,4-tetrahydro-6,7-dihydroxy-1-methyl-3-isoquinolinecarboxylic acid [(1RS,3RS)-1] was examined based on the melting point, solubility, and IR spectrum, with the aim of optical resolution by preferential crystallization. (1RS,3RS)-1 was indicated from these results to exist as a conglomerate. The successive optical resolution by preferential crystallization of (1RS,3RS)-1 yielded (1S,3S)- and (1R,3R)-1 with optical purities of 85--95% at 66--81% degrees of resolution, which were fully purified by recrystallization. 相似文献
16.
Yamada M Ichikawa T Yamano T Kikumoto F Nishikimi Y Tamura N Kitazaki T 《Chemical & pharmaceutical bulletin》2006,54(1):58-62
Two new synthetic methods were established for the efficient synthesis of optically active cyclohexene antisepsis agent, ethyl (6R)-6-[N-(2-chloro-4-fluorophenyl)sulfamoyl]cyclohex-1-ene-1-carboxylate [(R)-1: TAK-242)]. The first method involved recrystallization from methanol of the diastereomeric mixture (6RS,1'R)-7, obtained by esterification of carboxylic acid 3 with (S)-1-(4-nitrophenyl)ethanol [(S)-5)] to give the desired isomer (6R,1'R)-7 with 99% de in 32% yield. Subsequent catalytic hydrogenolysis and esterification gave (R)-1 with >99% ee. The second method employed enantioselective hydrolysis of acetoxymethyl ester 9a (prepared by alkylation of 3 with bromomethyl acetate) with Lipase PS-D to give the eutomeric enantiomer (R)-9a with excellent enantioselectivity (>99% ee) and high yield (48%). The desired (R)-1 was then obtained by transesterification with ethanol in the presence of concentrated sulfuric acid without loss of ee. Of these, the procedure employing enzymatic kinetic resolution using Lipase PS-D is the more efficient and practical preparation of (R)-1. 相似文献
17.
Aye Y Davies SG Garner AC Roberts PM Smith AD Thomson JE 《Organic & biomolecular chemistry》2008,6(12):2195-2203
tert-Butyl (RS)-3-methoxy- and (RS)-3-tert-butyldiphenylsilyloxy-cyclopent-1-ene-carboxylates display excellent levels of enantiorecognition in mutual kinetic resolutions with both lithium (RS)-N-benzyl-N-(alpha-methylbenzyl)amide and lithium (RS)-N-3,4-dimethoxybenzyl-N-(alpha-methylbenzyl)amide. A 50 : 50 pseudoenantiomeric mixture of lithium (S)-N-benzyl-N-(alpha-methylbenzyl)amide and lithium (R)-N-3,4-dimethoxybenzyl-N-(alpha-methylbenzyl)amide allows for the efficient parallel kinetic resolution of the tert-butyl (RS)-3-oxy-substituted cyclopent-1-ene-carboxylates, affording differentially protected 3-oxy-substituted cispentacin derivatives in high yield and >98% de. Subsequent N-deprotection and hydrolysis provides access to 3-oxy-substituted cispentacin derivatives in good yield, and in >98% de and >98% ee, while stereoselective epimerisation and subsequent deprotection affords the corresponding transpentacin analogues in good yield, and in >98% de and >98% ee. 相似文献
18.
Shiraiwa T Saijoh R Suzuki M Yoshida K Nishimura S Nagasawa H 《Chemical & pharmaceutical bulletin》2003,51(12):1363-1367
To obtain optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (1), (2RS,3SR)-2-benzoylamino-3-hydroxy-3-phenylpropanoic acid [(2RS,3SR)-2] was first optically resolved using (1S,2S)- and (1R,2R)-2-amino-1-(4-nitrophenyl)-1,3-propanediol as the resolving agents to afford (2R,3S)- and (2S,3R)-2 in yields of 73% and 66%, based on half of the starting amount of (2RS,3SR)-2. Next, the racemic structures of ammonium and some organic ammonium salts of (2RS,3SR)-2 were examined based on melting point, solubility, and infrared spectrum, with the aim of optical resolution by preferential crystallization. The benzylammonium salt of (2RS,3SR)-2 was suggested to exist as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization of the racemic salt afforded the (2R,3S)- and (2S,3R)-salts with optical purities of 90-97%. The (2R,3S)- and (2S,3R)-2 obtained from the purified salts were hydrolyzed by reflux in hydrochloric acid to give (2R,3S)- and (2S,3R)-1. 相似文献