The reaction of (E)-1-(2â²,3â²,4â²,6â²-tetra-O-acetyl-β-D-glucopyranosyloxy)-3-(trimethylsiloxy)buta-1,3-diene 1 and maleic anhydride gives cycloadduct 10 and ketone 12. Reduction of ketone 13, formed by acidic hydrolysis of silyl enol ether 10, with sodium cyanoborohydride in acetic acid gives an 83 â¶Â 17 mixture of the γ- and δ-lactone 14 and 15. γ-Lactone 14 is transformed into the aminomonocarba-disaccharide, 4-acetamido-2,4-dideoxy-3-O-(β-D-glucopyranosyl)-5a-carba-β-L-lyxo-hexopyranose 7, using a five-step procedure involving the Curtius rearrangement of acyl azide 16. A similar sequence using γ-lactone 21, prepared from ketone 12, gives the protected aminomonocarba-disaccharide, 4-acetamido-1,6-di-O-acetyl-2,4-dideoxy-3-O-(2â²,3â²,4â²,6â²-tetra-O-acetyl-β-D-glucopyranosyl)-5a-carba-β-D-lyxo-hexopyranose 8.
Reaction of cycloadduct 10 with dimethyldioxirane gives acyloin 26. Acetylation under acidic conditions followed by reduction with sodium cyanoborohydride in acetic acid gives a 75 â¶Â 25 mixture of the γ- and δ-lactone 28 and 29. Using a sequence similar to that employed for the preparation of compounds 7 and 8, γ-lactone 28 is converted into the fully substituted aminomonocarba-disaccharide, 4-acetamido-1,2,6-tri-O-acetyl-4-deoxy-3-O-(2â²,3â²,4â²,6â²-tetra-O-acetyl-β-D-glucopyranosyl)-5a-carba-β-L-galactopyranose 9.
(E)-1-(2â²,3â²,4â²,6â²-四-O-乙酰基-δ²-
D-吡喃葡萄糖氧基)-3-(三甲基
硅氧基)丁-1,3-二烯 1 与
马来酸酐反应生成环加成物 10 和酮 12。用
氰硼氢化钠在
乙酸中还原
硅烷基烯醇醚 10 酸性
水解形成的酮 13,得到 83Ââ¶Â17δ-和δ-内酯 14 和 15 的混合物。δ-内酯 14 通过酰基
叠氮 16 的 Curtius 重排等五步程序,转化成
氨基单胞二糖 4-乙酰
氨基-2,4-二脱氧-3-O-(δ-
D-吡喃葡萄糖基)-5a-δ-L-来苏
吡喃糖 7。使用由酮 12 制备的 δ³ 内酯 21 的类似步骤,可得到受保护的
氨基单卡巴二糖,即 4-乙酰
氨基-1,6-二-O-乙酰基-2,4-二脱氧-3-O-(2â²,3â²,4â²,6â²-O-四乙酰基-δ²-
D-吡喃葡萄糖基)-5a-carba-δ²-D-来苏己
吡喃糖 8。
环加合物 10 与
二甲基二环氧乙烷反应生成酰环 26。在酸性条件下进行乙酰化,然后用
氰硼氢化钠在
乙酸中进行还原,得到δ-和δ-内酯 28 和 29 的 75Ââ¶Â 25 混合物。采用与制备化合物 7 和 8 相似的方法,将δ-内酯 28 转化为完全取代的
氨基单胞菌二糖,即 4-乙酰
氨基-1,2,6-三-O-乙酰基-4-脱氧-3-O-(2â²,3â²,4â²,6â²-四-O-乙酰基-δ-
D-吡喃葡萄糖基)-5a-carba-δ-L-
吡喃半
乳糖 9。