Conversions of uronic acids [e.g. methyl 2, 3, 4-tri-O-methyl-β-D-glucopyranosiduronic acid (1), D-glucuronic acid (9), and D-galacturonic acid (17)] into the corresponding aminocyclitols [e.g. 6b, 7b, 8b ; 14b, c, 15b, c, 16b, c ; 18b] have been accomplished by means of initial electrolytic decarboxylation and subsequent treatment with alkaline nitromethane, followed by catalytic reduction, and acetylation. The conversion method has also been applied to neutral sugar [e.g. D-mannose (19)] to affording L-neo-aminocyclitol hexaacetate (22b) and also to two glucuronide-saponins [sakuraso-saponin (23) and desacyl-jegosaponin (27)] to afford aminocyclitol-oligoglycosides (26a, 28a). The present electrolytic conversion is noteworthy since prior protection of hydroxyl groups in the starting uronic acids is not necessary.
将
尿酸[如甲基 2,3,4-三-O-甲基-β-
D-吡喃葡萄糖苷酸 (1)、
D-葡萄糖醛酸 (9) 和
D-半乳糖醛酸 (17)]转化为相应的
氨基环糖醇[如6b、7b、8b;14b、c、15b、c、16b、c;18b]的转化是通过最初的电解脱羧和随后的碱性
硝基甲烷处理,再经过催化还原和乙酰化完成的。这种转化方法也适用于中性糖[如
D-甘露糖(19)],可得到 L-新
氨基环糖醇六
乙酸酯(22b),还适用于两种
葡萄糖醛酸
皂甙[sakuraso-
皂甙(23)和去酰基-积戈
皂甙(27)],可得到
氨基环糖醇
寡糖苷(26a、28a)。值得注意的是,这种电解转化无需事先保护起始
尿酸中的羟基。