Synthesis of a hexasaccharide fragment of the O-deacetylated GXM of C. neoformans serotype B
作者:Wei Zhao、Fanzuo Kong
DOI:10.1016/j.carres.2004.04.010
日期:2004.7
beta-(1-->4)-linked disaccharide 6. Deallylation followed by trichloroacetimidate formation gave the disaccharide donor 8, and subsequent coupling with allyl 2,3,4-tri-O-benzoyl-beta-D-xylopyranosyl-(1-->2)-4,6-di-O-benzoyl-alpha-D-mannopy ranoside (9), produced the tetrasaccharide 10. Reiteration of deallylation and trichloroacetimidate formation from 10 yielded the tetrasaccharide donor 12. The downstream disaccharide
beta-D-Xylp-(1-> 4)-alpha-D-Manp-(1-> 3)-[beta-D-Xylp-(1-> 2)]-alpha-D-Manp-合成了(1-> 3)-β-D-Xylp-(1-> 2)]-α-D-Manp,它是来自新隐球菌血清B的胞外多糖片段,作为其甲基糖苷。因此,对烯丙基3-O-苯甲酰基-4,6-O-亚苄基-α-D-甘露吡喃糖苷(1)进行乙酰化,然后进行脱苄基化和选择性6-O-苯甲酰化,得到烯丙基2-O-乙酰基-3,6-di -O-苯甲酰基-α-D-甘露吡喃糖苷(4)。用2,3,4-三-O-苯甲酰基-D-吡喃喃糖基三氯乙酰亚氨酸盐(5)对4进行糖基化,得到β-(1-> 4)连接的二糖6。并随后与烯丙基2,3,4-三-O-苯甲酰基-β-D-吡喃吡喃糖基-(1-> 2)-4,6-二-O-苯甲酰基-α-D-甘露糖核苷(9) ,产生四糖10。从10重复脱羧和形成三氯乙亚氨酸