Highly asymmetric Pummerer-type reaction induced by ethoxy vinyl esters
摘要:
Ethoxy vinyl esters (EVE:2) were efficient reagents for promoting the asymmetric Pummerer reaction with high enantioselectivity and high yield in contrast to the generally used acid anhydrides. Increasing the electron-donating ability on the R function in EVE 2 tended to increase enantioselectivity. Consequently, effective asymmetric rearrangements were achieved using EVEs 2b,c bearing a methoxybenzoyloxy function. (C) 1997 Elsevier Science Ltd.
The asymmetric totalsynthesis of the potent antitumor antibiotic fredericamycin A ((S)-1) was achieved by the intramolecular [4+2] cycloaddition of the silylene-protected styrene derivative (S)-7 followed by the aromatic Pummerer-type reaction of the sulfoxide (S)-5. Although we had already succeeded in the totalsynthesis of racemic 1 by the same approach, synthesis of its asymmetric version was
A linear approach to the totalsynthesis of racemic fredericamycin A (1) through the oxidative intramolecular [4 + 2] cycloaddition of a (phenylthio)acetylene-cobalt complex is described, which is applicable for the asymmetric totalsynthesis of naturally occuring 1. The highlight of this work is the aromaticPummerer-typereaction with 1-ethoxyvinyl chloroacetate, which effects the introduction of
first successful Pummerer-typereaction of the aromatic ring. In this review, we describe 1) the asymmetric Pummerer-typerearrangement induced by an O-silylatedketeneacetal, 2) the asymmetric Pummerer-typerearrangement induced by an ethoxy vinyl acetate, 3) the additive-Pummerer-type reaction, 4) the asymmetric Pummerer-type cyclization induced by an O-silylatedketeneacetal, and 5) the aromatic
Lipase-Catalyzed Asymmetric Desymmetrization of Prochiral 2,2-Disubstituted 1,3-Propanediols Using 1-Ethoxyvinyl Benzoate.
作者:Shuji AKAI、Tadaatsu NAKA、Yasushi TAKEBE、Yasuyuki KITA
DOI:10.1248/cpb.48.1519
日期:——
The lipase-catalyzed asymmetric desymmetrization of the prochiral 2, 2-disubstituted 1, 3-propanediols was studied using various types of 1-ethoxyvinyl esters (1a-i). Although 1a-e with aliphatic acyl groups were not sufficient, use of the benzoate (1f) in combination with Candida rugosa lipases converted acyclic diols (2, 6) and cyclic diols (11-14) to the optically active compounds (3f, 7f, 15f-18f), bearing a quaternary carbon center, with moderate-to-high optical yields. These products were fairly stable against racemization under acidic conditions.