The BF3·Et2O promoted coupling of tetra-O-benzyl-α-D-galactopyranosyl trichloroacetimidate with a silyl enol ether carrying an oxazolidine ring leads to the α-C-glycosylmethyl ketone (32%, 95% ds) that is converted into the title α-C-glycosyl amino acid by carbonyl oxygen removal (BartonâMcCombie) and oxidative cleavage (Jones) of the heterocyclic ring, and into the β-isomer by anomerization and the same two-step sequence.
BF3Â-Et2O 促进了四-O-苄基-δ-D-
吡喃半
乳糖基三
氯乙
酰亚胺与带有
恶唑烷环的
硅基烯醚的偶联,产生了δ-C-糖基甲基酮(32%、95%ds),通过杂环的羰基脱氧(巴顿-麦康比)和氧化裂解(琼斯)将其转化为标题中的δ-C-糖基
氨基酸,并通过异构化和相同的两步顺序将其转化为δ-异构体。