Total synthesis of(-)-grayanotoxin III (3), a unique tetracyclic diterpene isolated from the leaves of various plants of the family Ericaceae, has been successfully accomplished featuring the highly stereoselective cyclization reactions induced by SmI2.
Selectivity Guidelines and a Reductive Elimination-Based Model for Predicting the Stereochemical Course of Conjugate Addition Reactions of Organocuprates to γ-Alkoxy-α,β-enoates
作者:Artem S. Kireev、Madhuri Manpadi、Alexander Kornienko
DOI:10.1021/jo052383v
日期:2006.3.31
steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugateadditionreactions with cis and trans γ-alkoxy-α,β-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans
Alkylation and aldol reactions of acyl derivatives of N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine: asymmetric synthesis of α-alkoxy-, α-substituted-β-alkoxy- and α,β-dialkoxyaldehydes
作者:Alexander N. Chernega、Stephen G. Davies、Ai M. Fletcher、Christopher J. Goodwin、David Hepworth、R. Shyam Prasad、Paul M. Roberts、Edward D. Savory、Andrew D. Smith、James E. Thomson
DOI:10.1016/j.tet.2010.03.105
日期:2010.6
Treatment of a range of O-protected glycolate derivatives of the chiral auxiliary N-1-(1'-naphthyl)ethyl-O-tert-butylhydroxylamine with KHMDS in the presence of 18-crown-6 followed by addition of an alkyl halide generates alpha-substituted derivatives with very high levels of diastereoselectivity. Alternatively, reaction of the potassium enolate of a propanoate or O-protected glycolate derivative of N-1-(1'-naphthyl)ethyl-O-tert-butylhydroxylamine with a range of aldehydes gives syn-aldol products with high levels of diastereoselectivity. These adducts may be reductively cleaved with LiAlH(4) to give enantiopure alpha-alkoxy-, alpha-substituted-beta-alkoxy- and alpha,beta-dialkoxyaldehydes in good yield. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis of highly diastereo- and enantiomerically enriched tetracarbonyl(η3-allyl)iron(1+) complexes for allylic substitutions with silyl enol ethers and silyl ketene acetals
tetracarbonyl (η3-allyl)iron(1+) complexes 2a–d (2a–c: 20–53%, de > 90- ⩾ 95% or greater; 2d: 31–40%, ee ⩾ 99%) by means of an auxiliary controlled complexation (aux. = 8-phenylmenthyl) of diastereo- or of enantiopure (E)-configuration enoates 1 as starting materials is reported. The nucleophilic addition of various silyl enol ethers or silyl ketene acetals 3a–e to the complexes 2a–d followed by oxidative
Total synthesis of(-)-grayanotoxin III (3), a unique tetracyclic diterpene isolated from the leaves of various plants of the family Ericaceae, has been successfully accomplished featuring the highly stereoselective cyclization reactions induced by SmI2.