Steric effects in intramolecular [2+2] photocycloaddition of CC double bonds to cyclohexenones.
作者:D. Becker、N. Haddad
DOI:10.1016/s0040-4020(01)80336-7
日期:1993.1
The effect of substituents on the mode of approach and the endo/exo ratio in intramolecular [2+2] photocycloaddition reactions were studied.
研究了取代基对分子内[2 + 2]光环加成反应中接近方式和内/外比的影响。
Total Syntheses of Epothilones B and D
作者:Jae-Chul Jung、Rajashaker Kache、Kimberly K. Vines、Yan-Song Zheng、Panicker Bijoy、Muralikrishna Valluri、Mitchell A. Avery
DOI:10.1021/jo048742o
日期:2004.12.1
A convergent, totalsynthesis of epothilonesB (2) and D (4) is described. The key steps are Normant coupling to establish the desired (Z)-stereochemistry at C12−C13, Wadsworth−Emmons olefination of methyl ketone 28 with the phosphonate ester 8, diastereoselective aldol condensation of aldehyde 5 with the enolate of keto acid derivatives to form the C6−C7 bond, selective deprotection of acid 52, and
that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)‐italicene