Chemoselective Cross Metathesis of Bishomoallylic Alcohols: Rapid Access to Fragment A of the Cryptophycins
摘要:
The racemic or enantioselective allylation of in situ formed beta,gamma-unsaturated aldehydes provides efficient access to bishomoallylic alcohols from readily available 2-vinyloxiranes. These products, when subjected to modified Grubbs cross metathesis conditions, afforded terminally homologated products in moderate to good yields with high E selectivity and without degradation of the enantiomeric excess. The compounds obtained through this two-step sequence yield fragments of an important and pharmacologically active family of cryptophycins.
Enantioselective Allylation of <i>β</i><i>,</i><i>γ</i>-Unsaturated Aldehydes Generated via Lewis Acid Induced Rearrangement of 2-Vinyloxiranes
作者:Mark Lautens、Matthew L. Maddess、Effiette L. O. Sauer、Stéphane G. Ouellet
DOI:10.1021/ol016946a
日期:2002.1.1
[reaction: see text] 2-Vinyloxiranes have been found to be excellent surrogates to beta,gamma-unsaturated aldehydes. These valuable electrophiles, generated in situ by treatment of a 2-vinyloxirane with a catalytic amount of Sc(OTf)(3), are effectively trapped by the chiral allylating agents based on alpha-pinene, affording bishomoallylic alcohols in high yield and excellent selectivity.
Enzymatic Resolution of Chlorohydrins for the Synthesis of Enantiomerically Enriched 2-Vinyloxiranes
作者:Mark Lautens、J. McCubbin、Matthew Maddess
DOI:10.1055/s-2007-1000845
日期:2008.1
A series of vinylchlorohydrins are resolved by enzymatic kinetic resolution. The resulting R-alcohols, obtained in up to 99% ee, are stereoselectively converted into vinyloxiranes in high yield. The S-acetates, obtained in up to 99% ee were either deprotected to S-alcohols, or cyclized directly to vinyl oxiranes under basic conditions, with moderate to no loss in ee. The results are consistent with
通过酶动力学拆分来拆分一系列乙烯基氯醇。所得的 R-醇以高达 99% 的 ee 获得,以高产率立体选择性地转化为乙烯基环氧乙烷。以高达 99% ee 获得的 S-乙酸酯要么脱保护为 S-醇,要么在碱性条件下直接环化为乙烯基环氧乙烷,ee 中度至无损失。结果与涉及脱保护过程中醋酸盐可逆迁移的外消旋化机制一致。
Chemoselective Cross Metathesis of Bishomoallylic Alcohols: Rapid Access to Fragment A of the Cryptophycins
作者:Mark Lautens、Matthew L. Maddess
DOI:10.1021/ol049883f
日期:2004.6.1
The racemic or enantioselective allylation of in situ formed beta,gamma-unsaturated aldehydes provides efficient access to bishomoallylic alcohols from readily available 2-vinyloxiranes. These products, when subjected to modified Grubbs cross metathesis conditions, afforded terminally homologated products in moderate to good yields with high E selectivity and without degradation of the enantiomeric excess. The compounds obtained through this two-step sequence yield fragments of an important and pharmacologically active family of cryptophycins.
Synthesis of enantiopure chloroalcohols by enzymatic kinetic resolution
作者:Robert M. Haak、Chiara Tarabiono、Dick B. Janssen、Adriaan J. Minnaard、Johannes G. de Vries、Ben L. Feringa
DOI:10.1039/b613937j
日期:——
3-Alkenyl and heteroaryl chloroalcohols have been obtained in excellent enantiomeric excess (>99%) by enzymatic kinetic resolution using the haloalcohol dehalogenase HheC. Yields were close to the theoretical maximum for all substrates employed. Furthermore, the applicability of this methodology on multigram scale has been established.