Design and Use of an Oxazolidine Silyl Enol Ether as a New Homoalanine Carbanion Equivalent for the Synthesis of Carbon-Linked Isosteres of <i>O</i>-Glycosyl Serine and <i>N</i>-Glycosyl Asparagine
作者:Alessandro Dondoni、Alberto Marra、Alessandro Massi
DOI:10.1021/jo981861h
日期:1999.2.1
A trimethylsilyl enol ether carrying the N-Boc 2,2-dimethyloxazolidine ring was designed to serve as a synthetic equivalent of the homoalanine carbanion for the introduction of the alpha-amino acid side chain at the anomeric carbon of sugars. This new functionalized silyl enol ether was prepared in multigram scale and high enantiomeric purity starting from methyl N-Boc-L-threoninate (six steps, 49%
设计带有N-Boc 2,2-二甲基恶唑烷环的三甲基甲硅烷基烯醇醚,作为高丙氨酸碳负离子的合成等同物,用于在糖的异头碳处引入α-氨基酸侧链。从N-Boc-L-苏氨酸甲酯开始,以克级数和高对映体纯度制备这种新的官能化甲硅烷基烯醇醚(六步,收率49%)。该试剂用于C-糖基氨基酸的两种合成方法。在一种方法中,由BF(3).Et(2)O促进的与四-O-苄基-D-吡喃半乳糖基三氯乙酰亚胺酸酯的偶联提供了作为主要产物的α-连接的C-糖苷(分离出的收率为30%)用叔丁基锂转化为β-连接的异构体。通过Barton-McCombie方法对这些化合物进行脱氧,并通过琼斯试剂的氧化裂解从恶唑烷环上脱除糖基部分,从而得到C-糖基丝氨酸等位基因α-和β-Gal-CH(2)()-Ser。以类似的方式从四-O-苄基-D-吡喃葡萄糖基三氯乙酰亚胺酸酯开始制备α-和β-Glc-CH(2)()-Ser。在第二种方法中,在BF(