A Total Synthesis of Hydroxylysine in Protected Form and Investigations of the Reductive Opening of <i>p</i>-Methoxybenzylidene Acetals
作者:Tomas Gustafsson、Magnus Schou、Fredrik Almqvist、Jan Kihlberg
DOI:10.1021/jo049136w
日期:2004.12.1
A synthesis of (2S,5R)-5-hydoxylysine, based on (R)-malic acid and Williams glycine template as chiral precursors, has been developed. This afforded hydroxylysine, suitably protected for direct use in peptide synthesis, in 32% yield over the 13-step sequence. Regioselective reductive opening of a p-methoxybenzylidene acetal and alkylation of the Williams glycine template were key steps in the synthetic
(2的合成小号,5 - [R)-5- hydoxylysine,基于([R )-苹果酸和Williams甘氨酸模板作为手性前体,已经研制成功。这样得到的羟基赖氨酸经过适当保护,可直接用于肽合成,在13步序列中的收率为32%。对甲氧基亚苄基乙缩醛的区域选择性还原打开和威廉姆斯甘氨酸模板的烷基化是合成序列中的关键步骤。出人意料的是,p开口处的区域选择性与预期相比,将-甲氧基亚苄基缩醛逆转。发现这是由于在还原开口中用作亲电子试剂的三烷基甲硅烷基氯化物与相邻的叠氮化物官能团的螯合。还发现在反应中形成了等量的三烷基甲硅烷基氢化物,这一发现导致对用氰基硼氢化钠作为还原剂的对-甲氧基亚苄基乙缩醛的还原开口的进一步机理研究。