Chemo- and stereoselectivity in the ring-openingreaction of epoxides with a reagent prepared from allylmagnesium halide and chlorotitanium triphenoxide is described. It has been proven that the allylating reagent can also be used for the reaction of epoxides bearing a tert-butyl ester, amide, or acetal moiety, and that the epoxide cleavage regioselectively takes place at the more substituted carbon
REACTION OF OXIRANES WITH DIANION OF METHYL ACETOACETATE IN THE PRESENCE OF BORON TRIFLUORIDE ETHERATE
作者:Masahiko Yamaguchi、Ichiro Hirao
DOI:10.1246/cl.1985.337
日期:1985.3.5
Oxiranes were reacted with dianion of methyl acetoacetate in the presence of borontrifluoride etherate to give the substituted tetrahydro-2-furylideneacetates, which were further converted to γ-lactones.
Enantiocomplementary Chemoenzymatic Asymmetric Synthesis of (<i>R</i>)- and (<i>S</i>)-Chromanemethanol
作者:Michael Fuchs、Yolanda Simeo、Barbara T. Ueberbacher、Barbara Mautner、Thomas Netscher、Kurt Faber
DOI:10.1002/ejoc.200800950
日期:2009.2
route towards enantiopure (R)- and (S)-chromanemethanol (12), which are the key buildingblocks for the synthesis of stereoisomerically pure α-tocopherols, has been achieved by the biocatalytic resolution of a racemic 2,2-disubstituted oxirane using an epoxide hydrolase and a halohydrindehalogenase, which exhibit opposite enantiopreferences. The introduction of chirality at an early stage of the synthesis
Selectivity enhancement of enantio- and stereo-complementary epoxide hydrolases and chemo-enzymatic deracemization of (±)-2-methylglycidyl benzyl ether
作者:Yolanda Simeó、Kurt Faber
DOI:10.1016/j.tetasy.2005.12.018
日期:2006.2
The kinetic resolution of (+/-)-2-methylglycidyl benzyl ether was achieved via enantioselectivc biohydrolysis using microbial and plant epoxide hydrolases. Depending on the type of enzyme, opposite enantiopreference and stereo-complementary mode of action (i.e., retention vs inversion of configuration) led to hetero- and homochiral product mixtures. optimization of the reaction conditions for Rhodococcus sp. R312 led to significantly enhanced enantioselectivity (E > 200), which enabled the deracemization of (+/-)-2-methylglycidyl benzyl ether via biohydrolysis (proceeding with retention of configuration) followed by inverting acid-catalyzed hydrolysis to furnish (R)-1-benzyloxy-2-methylpropane-2,3-diol in > 97% ee and 78% yield from the racemate. (c) 2006 Elsevier Ltd. All rights reserved.
An alternative approach to (S)- and (R)-2-methylglycidol O-benzyl ether derivatives
作者:Alberto Avenoza、Carlos Cativiela、Jesús M. Peregrina、David Sucunza、Marı́a M. Zurbano
DOI:10.1016/s0957-4166(01)00230-0
日期:2001.6
This report describes the gram scale synthesis of (S)- and (R)-2,2,4-trimethyl-4-(hydroxymethyl)-1,3-dioxolanes using the Sharpless asymmetric dihydroxylation (AD) of the Weinreb amide of 2-methyl-2-propenoic acid. The 2-methylglycerol acetonides resultant from protection of the AD products were used as starting materials in the synthesis of O-benzyl ethers of the valuable C4-chiral building blocks (S)- and (X)-2-methylglycidol. (C) 2001 Elsevier Science Ltd. All rights reserved.