6-o-三苯甲基-α-甲基-d-葡萄吡喃甙的高碘酸盐氧化的区选性

进行了6-o-三苯甲基-a-甲基-d-葡萄吡喃甙(TMGP,I)在 THF-水和在 DMF-水中的高碘酸盐氧化反应。以亚砷酸钠滴定跟踪的高碘酸盐消耗-时间曲线表明,氧化明显地比在水中缓慢,消耗一克分子高碘酸盐的时间分别约为6.4(THF-水,23℃)和20(DMF-水,12℃)小时,而且在此之后的氧化更为缓慢。以a-甲基-d-葡萄吡喃甙(MGP)作为对照在水、THF-水和DMF-水中进行相同的氧化反应消耗一克分子高碘酸盐的时间约为<0.2(水,26℃)、2(THF-水,25℃)和2.6(DMF-水,26℃)小时。此外,在TMGP的情况中,滴定曲线在消耗等克分子高碘酸盐的前后有一明显的转折;在此之前几乎不生成甲酸,而在转折后的近处仅含2—3％的甲酸。     

Highly Efficient Regio- and Stereoselective Synthesis of β-（1 →6）-Branched β-（1 →3）-Linked Glucohexaose and Its Analogue

A β-（1→）6）-branched β-（1→）3）-linked glucohexaose （1） and its lauryl glycoside （2）, present in many biologically active polysaccharides from traditional herbal medicines such as Ganoderma lucidum, Schizophyllum commune and Lentinus edodes, were highly efficiently synthesized. Coupling of 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl- （1--）3）-2-O-benzoyl-4,6-O-benzylidene-a-D-glucopyranosyl trichloroacetimidate （7） with 3,6-branched acceptors 8 and 12 gave β-（1→）3）-linked pentasaccharides （9） and （13）, then via simple chemical transformation 4＇,6＇-OH pentasaccharide acceptors 10 and 14 were obtained. Regio- and stereoselective coupling of 3 with 10 and 14 gave β-（1→）3）-linked hexasaccharides （11） and （15） as the major products. Deprotection of 11 and 15 provided the target sugar 1 and 2. Thus, a new method for the preparation of this kind of compounds was developed.