Elemental sulfur reacts with conjugated 1,3-dienes to deliver cyclic di- and polysulfides; the reaction proceeds without any activation other than heat. Treatment of cyclic polysulfide products with triphenylphosphine cleanly converts them to the corresponding disulfide in good overall yield. Additionally, some mechanistic aspects have been examined. The presence of disulfur as an active species in the sulfuration of dienes with S-8 is discussed. (C) 1997 Elsevier Science Ltd.
The stereochemical course of 2-methylisoborneol biosynthesis
作者:Binbin Gu、Anwei Hou、Jeroen S Dickschat
DOI:10.3762/bjoc.18.82
日期:——
Both enantiomers of 2-methyllinalyl diphosphate (2-Me-LPP) were synthesized enantioselectively using Sharpless epoxidation as a key step and purification of enantiomerically enriched intermediates through HPLC separation on a chiral stationary phase. Their enzymatic conversion with 2-methylisoborneol synthase (2MIBS) demonstrates that (R)-2-Me-LPP is the on-pathway intermediate, while a minor formation
使用 Sharpless 环氧化作为关键步骤,并通过手性固定相上的 HPLC 分离纯化对映体富集的中间体,对映体选择性地合成了 2-甲基芳樟基二磷酸 (2-Me-LPP) 的两种对映体。它们与 2-甲基异冰片合酶 (2MIBS) 的酶促转化表明 ( R )-2-Me-LPP 是通路中间体,而从 ( S )-2-Me-LPP形成少量 2-甲基异冰片可以解释异构化为 2-Me-GPP,然后异构化为 ( R )-2-Me-LPP。
Elemental sulfur reacts with conjugated 1,3-dienes to deliver cyclic di- and polysulfides; the reaction proceeds without any activation other than heat. Treatment of cyclic polysulfide products with triphenylphosphine cleanly converts them to the corresponding disulfide in good overall yield. Additionally, some mechanistic aspects have been examined. The presence of disulfur as an active species in the sulfuration of dienes with S-8 is discussed. (C) 1997 Elsevier Science Ltd.
A General Nickel-Catalyzed Kumada Vinylation for the Preparation of 2-Substituted 1,3-Dienes
nickel(II) precatalysts for the preparation of 2-substituted 1,3-dienes by a Kumada cross-coupling between vinyl magnesium bromide and vinyl phosphates is described. This is noteworthy as engaging only one vinyl derivative in a transition-metal-catalyzed cross-coupling reaction is already reputedly challenging. Salient features of this method are its operational simplicity, the mild reaction conditions, the