Oxazaborolidine catalysed enantioselective reduction of cyclic meso-imides
摘要:
Full details of the enantioselective reduction of cyclic meso-imides catalysed by an enantiopure oxazaborolidine derived from (S)-alpha,alpha-diphenylprolinol are reported. Treatment of the imides with borane in the presence of the catalyst led to a mixture of cis- and trans-hydroxylactams and, after subsequent ethanolysis, to the corresponding diastereomerically pure trans-ethoxylactams. The enantiomeric excesses were shown to be 68-94% by HPLC-determination. One example, in which the ethoxylactam was converted into the benzenesulfonyllactam, could be crystallized to >99% enantiomeric purity. (C) 1997 Elsevier Science Ltd.
Enantioselective Reduction of meso-Cyclic-1,2-dicarboxylic Anhydrides and 1,2-Dicarboximides: Asymmetric Synthesis of Bicyclic Lactones and Hydroxylactams.
Selective reduction of αβ-olefinic amides and lactams by magnesium and methanol
作者:Roger Brettle、Sa'ad M. Shibib
DOI:10.1039/p19810002912
日期:——
αβ-Olefinicamides with various substitution patterns at the carbon–carbon double bond and at nitrogen are all reduced to the corresponding saturated amides by magnesium and methanol. The same reducing system reduces N-benzyl-8-azabicyclo[4.3.0]nona-1(6),3-dien-7-ones at the conjugated double bond to give mixtures of the cis-and trans-dihydro-derivatives; the isolated, non-conjugated double bond is
在碳-碳双键和氮上具有各种取代方式的αβ-烯烃酰胺都被镁和甲醇还原为相应的饱和酰胺。相同的还原体系将共轭双键处的N-苄基-8-氮杂双环[4.3.0] nona-1(6),3-dien-7-还原为顺式和反式二氢衍生物的混合物。分离的非共轭双键即使在3,4-二苯基取代的化合物中也不会还原。镁和甲醇降低喹啉-2(1 H ^) -酮其3,4-二氢衍生物,和5,6,7,8-四氢喹啉-2(1 H ^) -酮于两个二氢衍生物的混合物。
Stereocontrol in the reduction of meso-imides using oxazaborolidine, leading to a facile synthesis of (+)-deoxybiotin
Highly enantioselective reduction of meso-imides was conducted using oxazaborolidine derived from L-threonine and borane-THF complex to give lactams in high enantiomeric purity. This methodology was successfully applied to the synthesis of (+)-deoxybiotin in an enantio-controlled manner in good overall yield. (C) 1999 Elsevier Science Ltd. All rights reserved.
Oxazaborolidine catalyzed enantioselective reductions of cyclic meso-imides
作者:Romeo Romagnoli、Eric C. Roos、Henk Hiemstra、Marinus J. Moolenaar、W. Nico Speckamp、Bernard Kaptein、Hans E. Schoemaker
DOI:10.1016/s0040-4039(00)79972-2
日期:1994.2
A new asymmetric reduction method for meso-imides is reported. Treatment of various imides with a mixture of a chiral oxazaborolidine and BH3 leads to a mixture of cis- and trans-hydroxylactams and, after subsequent ethanolysis, to the corresponding diastereomerically pure trans-ethoxylactams. The enantiomeric excesses were shown to be 75-89% by both chiral HPLC-determinations and conversion of the reduction products into the corresponding, known lactones.