糖类研究（ⅩⅩⅤ）

Studies on Carbohydrates (XXV)──Synthesis of Disaccharide Units of Serratia marcescens O4 Antigen Oligosaccharide

利用三氟乙酰氧基、三氯乙酰氧基和三氯乙酰亚胺基作为糖端基离去基团，在Ｌｅｗｉｓ酸催化下合成了粘质沙雷氏菌Ｏ４抗原寡糖片段，反应条件温和，收率良好，三氟乙酸酯和三氯乙酸酯法具有很好的立体选择性，运用波谱法方法确定了所有化合物的结构。

A blocked disaccharide portion of the biological repeat unit, [→4) α-D-Glcp (1→3)-α-L-Rhap (AcO→2) (1→] of the Serratia marcescens O4 oligosaccharide wasprepared by using 1-O-trlfluoroacetoxy, trlchloroacetoxy or trichloroacetimido as leaving groupof sugar in the presence of Lewis acid. The reaction conditions were very mild, and theyields were also good. Trlfluoroacetoxy and trlchloroacetoxy are good leaving groups and af-ford the 1products in a high stereoselectivity. All compounds were confirmed by IR, MS, Hand 13C NMR spectral methods.