Mulard L A, Kovác P, Glaudemans C P
NIDDK, National Institutes of Health, Bethesda, MD 20892.
Carbohydr Res. 1994 Jan 3;251:213-32. doi: 10.1016/0008-6215(94)84287-6.
The title disaccharides were synthesized by condensation of 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl bromide with suitably protected, deoxygenated derivatives of methyl alpha-D-galactopyranoside. Deoxygenation was achieved via activation of a protected methyl alpha-D-gluco- or galacto-pyranoside with N,N'-thiocarbonyldiimidazole followed by treatment with tributyltin hydride and azobisisobutyronitrile. At position 3, the deoxygenation was more successful when performed with the tri-O-benzoylated precursor, rather than the tri-O-benzylated one. The corresponding nucleophile was obtained by benzylidenation of the methyl 3-deoxy-alpha-D-xylo-hexopyranoside. The preparation of the glycosyl acceptor deoxygenated at position 4 could be pursued starting from derivatives having either the D-galacto or the D-gluco configuration. The pathway involving the former was found superior.
通过将2,3,4-三-O-苯甲酰基-α-L-鼠李吡喃糖基溴与适当保护的、脱氧的α-D-吡喃半乳糖苷甲基衍生物缩合，合成了标题二糖。通过用N,N'-硫代羰基二咪唑活化受保护的α-D-吡喃葡萄糖苷或吡喃半乳糖苷甲基，然后用三丁基氢化锡和偶氮二异丁腈处理来实现脱氧。在3位，用三-O-苯甲酰化前体进行脱氧比用三-O-苄基化前体更成功。相应的亲核试剂是通过3-脱氧-α-D-吡喃木糖己糖苷甲基的亚苄基化获得的。4位脱氧的糖基受体的制备可以从具有D-吡喃半乳糖或D-吡喃葡萄糖构型的衍生物开始进行。发现涉及前者的途径更优。
