Substrate modification to increase the enantioselectivity of hydrolases. A route to optically-active cyclic allylic alcohols.
摘要:
The esterase-catalyzed resolution of the cyclic allylic acetates - 1-acetyloxy-2-cyclopentene, 1-acetyloxy-2-cyclohexene, and 1-acetyloxy-2-cycloheptene - was not enantioselective. We hypothesized that this inefficiency stems from the similarity in size of the substituents at the stereocenter (CH2-CH2 vs. CH=CH). To increase the enantioselectivity, we resolved precursors to these cyclic allylic alcohols: esters of trans-2-bromocycloalkanols (C5, C6, C7). These esters had a larger difference in the size of the substituents (CH2 vs. CHBr) at the stereocenter and were efficiently resolved by both cholesterol esterase and lipase from Pseudomonas cepacia (Amano P, PCL). A synthetic-scale resolution with PCL yielded the (1S,2S)-1-butanoyloxy-2-bromocycloalkanes in >98% ee. Heating with DBU to eliminate HBr, followed by reduction with LiAlH4 to cleave the ester, yielded the allylic alcohols: (S)-(-)-2-cyclopenten-1-ol (65% ee), (S)-(-)-2-cyclohexen-1-ol (>99% ee), and (S)-(-)-2-cyclohepten-1-ol (>98% ee).
Metal(II)<i>d</i>-Tartrates Catalyzed Asymmetric Ring Opening of Oxiranes with Various Nucleophiles
作者:Hiroyuki Yamashita
DOI:10.1246/bcsj.61.1213
日期:1988.4
The asymmetricringopening of meso-2,3-disubstituted oxiranes with thiols, aniline, and trimethylsilyl azide was studied by the use of metal(II) d-tartrates as heterogeneous chiral Lewis acid catalysts. The enantioselectivity varied widely with the combination of oxirane, nucleophile, and metal(II) d-tartrate, and Zn(II) d-tartrate gave the best enantioselectivity in the respective reactions of 1
通过使用金属 (II) d-酒石酸盐作为非均相手性路易斯酸催化剂,研究了具有硫醇、苯胺和三甲基甲硅烷基叠氮化物的 meso-2,3-di 取代的环氧乙烷的不对称开环。对映选择性随环氧乙烷、亲核试剂和金属 (II) d-酒石酸盐的组合而变化很大,并且 Zn(II) d-酒石酸盐在 1,2-环氧环己烷与 1-丁硫醇、苯胺、和三甲基甲硅烷基叠氮化物分别以 85%、58% 和 42% ee 提供相应的加合物。此外,研究了由 Zn(II) d-酒石酸盐催化的具有硫醇的外消旋环氧乙烷的动力学拆分。
Palladium(II)-catalyzed dicarboxymethylation of chiral allylic alcohols: chirality transfer affording optically active diesters containing three contiguous chiral centers
作者:Othman Hamed、Patrick M. Henry、Daniel P. Becker
DOI:10.1016/j.tetlet.2010.04.105
日期:2010.7
This manuscript describes the extension of Stille’s palladium-catalyzed olefin dicarbonylation reaction to chiralallylicalcohols with chiralitytransfer to afford the corresponding chiralalcohol functionalized with bis-carbomethoxy esters, containing three contiguous chiral centers, in good to excellent diastereoselectivities (78–98%).
Asymmetric reduction of α,β-unsaturated ketones with chiral hydride reagents prepared from lithium aluminum hydride and (S)-4-anilino- and (S)-4-(2,6-xylidino)-3-methylamino-1-butanol
The asymmetric reduction of prochiral α,β-unsaturated ketones with chiralhydride reagents derivedfromlithium aluminum hydride and (S)-4-anilino- and (S)-4-(2,6-xylidino)-3-methylamino-1-butanol gives (S)- and (R)-allylic alcohols in high chemical and optical yields, respectively.
Asymmetric Trasformation of Symmetrical Epoxides to Allylic Alcohols by Lithium (<i>S</i>)-2-(<i>N</i>,<i>N</i>-Disubstituted aminomethyl)pyrrolidide
作者:Masatoshi Asami
DOI:10.1246/bcsj.63.721
日期:1990.3
Enantioselective deprotonation of symmetrical epoxides was studied by using chiral lithium amide, prepared from (S)-2-(N,N-disubstituted aminomethyl)pyrrolidine and butyllithium. Chiral allylic alcohols were obtained with moderate to high enantiomeric excesses (ee’s) (41–92% ee) from several cyclic and acyclic epoxides employing lithium (S)-2-(1-pyrrolidinylmethyl)pyrrolidide in tetrahydrofuran (THF) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).
Catalytic enantioselective rearrangement of meso-epoxides mediated by chiral lithium amides in the presence of excess cross-linked polymer-bound lithium amides
作者:Atsushi Seki、Masatoshi Asami
DOI:10.1016/s0040-4020(02)00371-x
日期:2002.6
Insoluble polymer-bound achiral lithium dialkylamides were prepared from the corresponding cross-linked polymer-bound amines and butyllithium. The polymer-bound achiral reagent was applied to a catalytic enantioselective rearrangement of meso-epoxides as an in situ regenerating agent of a chiral lithiumamide. The efficiency of the catalytic system was improved, and chiral allylic alcohol derivatives