peracetylated disaccharide derivative (6). The structures of 5 and 6 were established by 1H-n.m.r. spectroscopy. O-Deacetylation of 6 afforded the title beta-(1 leads to 3)-linked disaccharide 7. For the synthesis of the beta-(1 leads to 2)-linked isomer, methyl 3-O-benzoyl-4,6-O-benzylidene-alpha-D-galactopyranoside was similarly condensed with bromide 1 to give the fully protected disaccharide derivative
2-O-苯甲酰基-4,6-O-亚苄基-α-D-
吡喃半
乳糖苷与3,4,6-三-O-乙酰基-2-脱氧-2-邻苯二甲
酰亚胺-β-
D-吡喃葡萄糖基
溴化物的缩合反应( 1)在
二氯甲烷中,在
三氟甲磺酸银,2,4,6-三
甲基吡啶和
分子筛的存在下,获得甲基2-O-苯甲酰基-4,6-O-亚苄基-3-O-(3,4,6 -三-O-乙酰基-2-脱氧-2-邻苯二甲
酰亚胺基-β-
D-吡喃葡萄糖基)-α-D-
吡喃半
乳糖苷(4)。在热的80%
乙酸水溶液中将4脱
缩醛化,得到甲基2-O-苯甲酰基-3-O-(3,4,6-三-O-乙酰基-2-脱氧-2-邻苯二甲
酰亚胺基-β-
D-吡喃葡萄糖基) -α-
D-半乳糖吡喃糖苷(5),其在脱酰后再进行过乙酰化,得到过乙酰化的二糖衍
生物(6)。5和6的结构通过1H-nmr光谱确定。6的O-脱乙酰基制得标题β-(1导致3)连接的二糖7。对于β-(1导致2)连接的异构体的合成,甲基3-O-苯甲酰基-4