β-d-Ribofuranosyl-(1→3)-α-l-rhamnopyranosyl-(1→3)-l-rhamnopyranose, the trisaccharide repeating unit of the C. freundii O28,1c O-specific polysaccharide, was synthesized using in situ activating glycosylation of the 1-OH sugar derivatives and a reagent mixture of trimethylsilyl bromide, cobalt(II) bromide, tetrabutylammonium bromide, and molecular sieves 4A. Regioselective tritylation was useful for synthesizing the 3-OH derivatives of methyl, allyl, and benzyl α-l-rhamnosides.
β-d-
核糖呋喃糖-(1→3)-α-l-
鼠李糖琥珀糖-(1→3)-l-
鼠李糖,作为C. freundii O28,1c O特异性
多糖的三糖重复单元,采用原位活化糖苷化的方法合成,涉及1-OH糖衍
生物和三甲基
硅基
溴、
钴(II)
溴化物、
四丁基溴化铵及4A
分子筛的试剂混合物。区域选择性三苯基甲基化对于合成甲基、烯丙基和苄基α-l-
鼠李糖苷的3-OH衍
生物非常有效。