Enzymatic desymmetrization of meso-1α,4α-dihydroxy-cis-decalins
摘要:
The stereoselective acetylation of meso-decalindiols I and 2 by vinyl acetate in the presence of Candida antarctica lipase gave monoester (1R,4S,4aR,8aS)-5 and (1R,4S,4aR,8aS)-6 in high enantiomeric excess (ee greater than or equal to 98%). The hydrolysis of the corresponding meso-diacetates 3 and 4 in the presence of porcine liver esterase in phosphate buffer provided the opposite enantiomers. (C) 2004 Elsevier Ltd. All rights reserved.
reaction of different carbonylcompounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonylcompounds into the corresponding
Stereo- and chemoselective transfer hydrogenation of carbonyl groups with RuCl2(PPh3)3 and BINAP-Ru as catalysts and Et3NH+H2PO2−·1,5H2O as a hydrogen donor
作者:Bui The Khai、Antonio Arcelli
DOI:10.1016/0040-4039(96)01476-1
日期:1996.9
Using Et3NH+H2PO2−.1.5 H2O as a hydrogendonor, the RuCl2(Ph3P)3, and BINAP-Ru proved highly active catalysts for transferhydrogenation of ketones under milder conditions than other hydrogendonors. 2-Methyl-, 2-chloro-, 2-(ethoxy-carbonyl)cyclohexanones and -cyclopentanones were reduced to the less stable axial alcohols in excellent diastereoisomeric excess (de: 90–100%), and the carbonylgroup of α
A selective C–H insertion/olefination protocol for the synthesis of α-methylene-γ-butyrolactone natural products
作者:Matthew G. Lloyd、Mariantonietta D'Acunto、Richard J. K. Taylor、William P. Unsworth
DOI:10.1039/c5ob02579f
日期:——
A regio- and stereoselective one-pot C–H insertion/olefination protocol has been developed for the late stage installation of α-methylene-γ-butyrolactones into conformationally restricted cyclohexanol-derivatives.
Eight novel NAD(H)‐dependent HSDHs, showing either 7α‐, 7β‐, or 12α‐HSDH activity, and including, for the first time, enzymes from extremophilic microorganisms, were identified, recombinantly produced, and characterized. Among the novel HSDHs, four highly active (up to 92 U mg−1) NAD(H)‐dependent 7β‐HSDHs showing negligible similarity towards previously described 7β‐HSDHs, were discovered.
羟基类固醇脱氢酶(HSDHs)是用于类固醇,胆汁酸和其他类固醇衍生物的区域和立体选择性修饰的有价值的生物催化剂。在这项工作中,我们研究了这种高度选择性的酶的底物混杂。为了实现此目标,对内部或公共(元)基因组中的HSDH同源物进行了初步搜索。八种新颖的NAD(H)依赖性HSDHs表现出7α-,7β-或12α-HSDH活性,并首次鉴定,重组产生和鉴定了包括极端微生物的酶。在新的HSDH中,发现了四个高度活性(高达92 U mg -1)的NAD(H)依赖性7β-HSDH,与先前描述的7β-HSDH的相似性可忽略不计。
Does substituent's conformation influence the kinetics of reduction reactions on trans-4-X-decal-1-ones and to what extent?
作者:Giorgio Di Maio、Maria Gabriella Mascia、Elisabetta Vecchi
DOI:10.1016/s0040-4020(02)00303-4
日期:2002.4
Stereochemistry and relative rates kax and keq of reduction reactions on title compounds have been measured under five different reaction conditions (NaBH4 in i-PrOH, LiBH4 and NaAlH4 in THF and LiAlH4 in THF and in Et2O). Experiments indicate that axial substituents behave as far less electronegative than their equatorial counterpart in reactions at the equatorial side of molecules.