Highly Stereoselective Peptide Modifications through Pd-Catalyzed Allylic Alkylations of Chelated Peptide Enolates
作者:Jan Deska、Uli Kazmaier
DOI:10.1002/chem.200700084
日期:2007.7.16
Deprotonation of peptides in the presence of zinc chloride gives rise to highly reactive nucleophiles that can be subjected to palladium-catalyzed allylic alkylation reactions. Excellent diastereoselectivities are obtained that are nearly independent of the allylic substrate used. By using this protocol, highly functionalized side chains can also be incorporated in excellent yields and selectivities
在氯化锌的存在下,肽的去质子化反应产生了高反应性亲核试剂,该亲核试剂可以进行钯催化的烯丙基烷基化反应。获得了极好的非对映选择性,几乎与所用的烯丙基底物无关。通过使用该协议,高度功能化的侧链也可以以优异的收率和选择性掺入。只要涉及末端π-烯丙基-钯配合物,反应的立体化学结果就完全由肽链控制。可能,去质子化的肽链与螯合的锌离子至少有三重配位。在此类金属肽络合物中,生成的烯醇化物的一个面被相邻氨基酸的侧链屏蔽,从而将亲电攻击指向相反的一面。此行为解释了为什么S氨基酸总是生成R氨基酸(反之亦然)的原因。