The addition of the lithium derivative of N-Boc 4-ethynyl-2,2-dimethyl-1,3-oxazolidine to tetra-O-benzyl-d-gluco- and galactonolactone and 2-azido-2-deoxy congeners afforded the corresponding ethynyl ketoses in fairly good yields (64-78%). Following the conversion of the ketoses into O-acetates and removal of the acetoxy group by silane reduction, the resulting β-linked ethynyl glycosides were transformed into N-Boc C-glycosyl α-aminobutyric acids by reduction of the triple bond using H2/Pd(OH)2 and oxidative cleavage of the oxazolidine ring using the Jones’ reagent. After the removal of O-benzyl groups of the carbohydrate moieties by hydrogenation and the reduction of azido to amino group, all compounds were subjected to acetylation and isolated as O- and N-acetyl derivatives. The C-glycosyl α-amino acids prepared correspond to methylene isosteres of O-glycosyl serines.
将N-Boc 4-
乙炔基-2,2-二甲基-1,3-
噁唑烷的
锂衍
生物与四-O-苄基-d-
葡萄糖和d-半
乳糖内酯以及2-
叠氮-2-脱氧同系物反应,得到相应的
乙炔基酮,产率相当不错(64-78%)。在将酮转化为O-
醋酸酯并通过
硅烷还原去除
醋酸氧基后,得到的β-连接
乙炔基糖苷通过使用H2/Pd(OH)2还原三重键和利用琼斯试剂氧化开环将
噁唑烷环转化为N-Boc C-糖苷 α-
氨基
丁酸。在通过氢化去除糖部分的O-苄基后,并将
叠氮基还原为
氨基后,所有化合物均经
过醋酸化处理,并以O-和N-
醋酸衍
生物的形式分离出来。所制备的C-糖苷
α-氨基酸对应于O-糖苷
丝氨酸的亚甲基等构体。