rac-trans-haloalkyl epoxides 1a−8a using the epoxide hydrolase activity of whole bacterial cells furnished the corresponding vicinal diols 1b−8b as intermediates; these (spontaneously) underwent ring closure to yield cyclic products 1c−6c through an enzyme-triggered cascade reaction. In particular, cis-configured substrates (1a, 3a, 5a, 7a) were transformed in an enantioconvergent fashion, which resulted
使用整个细菌细胞的环氧水解酶活性对 2,3-二取代外消旋-顺-和外消旋-反-卤代烷基环氧化物 1a-8a 进行生物催化水解,得到相应的邻位二醇 1b-8b 作为中间体;这些(自发地)经历闭环以通过酶触发的级联反应产生环状产物 1c-6c。特别是,顺式构型的底物(1a、3a、5a、7a)以对映收敛方式转化,导致从外消旋体中形成 100% des 和高达 92% ees 的单一立体异构产物。
Chemoenzymatic asymmetric total syntheses of a constituent of Jamaican rum and of (+)-Pestalotin using an enantioconvergent enzyme-triggered cascade reaction
作者:Sandra F. Mayer、Andreas Steinreiber、Marian Goriup、Robert Saf、Kurt Faber
DOI:10.1016/s0957-4166(02)00124-6
日期:2002.4
(−)-Pestalotin—was accomplished based on an enzyme-triggered cascade-reaction. Thus, a racemic halomethyl oxirane was hydrolyzed by bacterial epoxide hydrolases to furnish the corresponding vic-halomethyl-diol, which underwent spontaneous ring-closure to furnish an epoxy alcohol in up to 93% e.e. and ≥99 d.e. Due to the fact that this process was enantioconvergent, the occurrence of the undesired enantiomer
Stereoselective reduction of α,β-epoxy ketones with sodium borohydride in the presence of calcium chloride or lanthanum chloride. A practical preparation of erythro-α,β-epoxy alcohols
erythro-Epoxy alcohols were prepared with high stereoselectivity by NaBH4 reduction of the corresponding α,β-epoxyketones in the presence of calcium chloride or lanthanum chloride regardless of the substituents on the epoxide ring.
α,β-Epoxyketones are reduced by trimethoxysilane in the presence of a catalytic amount of lithium methoxide to yield the corresponding alcohols. This reaction system reveals divergent selectivity depending on the solvent; both anti-selectivity and syn-selectivity are observed iin less polar Et2O and in polar HMPA, respectively.
Stereoselective Reduction of α,β-Epoxy Ketones into erythro-α,β-Epoxy Alcohols with Sodium Borohydride in the Presence of Calcium Chloride
作者:Hideaki Fujii、Koichiro Oshima、Kiitiro Utimoto
DOI:10.1246/cl.1992.967
日期:1992.6
erythro-α,β-Epoxyalcohols were prepared with high stereoselectivity by sodium borohydride reduction of the corresponding α,β-epoxyketones in the presence of calcium chloride or manganese(II) chloride regardless of the substituents on the epoxide ring.
无论环氧化物环上的取代基如何,在氯化钙或氯化锰 (II) 存在下,通过硼氢化钠还原相应的 α,β-环氧酮,以高立体选择性制备赤型-α,β-环氧醇。