Has a nice ring to it: A concise and modular totalsynthesis of the naturally occurring antibiotic virginiamycin M2 is described. A Barbier‐type cyclization was used to close the 23‐membered macrocycle and deliver virginiamycin M2 in 19 steps from a chiral organosilane.
Regioselective Carboxylation of Silicon-Stabilized Allylic Carbanions and the Synthetic Utility of 2-Silyl-3-butenoates
作者:Hidemitsu Uno
DOI:10.1246/bcsj.59.2471
日期:1986.8
Carbanions of allylic dimethylphenylsilanes show remarkable regioselectivity toward both carboxylation with carbon dioxide and methylation with methyl iodide. Methylation of these compounds occurred preferentialy at α position, although allyltrimethylsilane and allyltriphenylsilane are known to give γ selectivity toward the same electrophiles. Moreover, their aluminum “ate” complexes react with carbon
烯丙基二甲基苯基硅烷的碳负离子对二氧化碳的羧化和甲基碘的甲基化都显示出显着的区域选择性。这些化合物的甲基化优先发生在 α 位,尽管已知烯丙基三甲基硅烷和烯丙基三苯基硅烷对相同的亲电试剂具有 γ 选择性。此外,它们的铝“ate”复合物在 a 位置与二氧化碳发生区域选择性反应,而与烯丙基部分的甲基取代模式无关。α-羧化烯丙基硅烷被证明是酯化后 3-(甲氧基羰基)烯丙基阴离子的有用合成子。
Regioselective SN′ allylic substitution versus 1,4-addition: Synthesis of α-substituted β,γ-unsaturated esters
作者:C Girard、I Romain、M Ahmar、R Bloch
DOI:10.1016/s0040-4039(00)70708-8
日期:1989.1
The reaction of the higher order organocuprate reagents R2Cu(CN)Li2-BF3 with γ-bromo α,β-unsaturated estersgives with very high selectivity α-substituted β,γ-unsaturated esters arising from a SN′ allylic substitution. This reaction allows an easy access to α-silyl β,γ-unsaturated esters.