α-pyranoside (6). Methylation of the free hydroxyl groups of 5 and 6 gave the respective per-O-methyl derivatives 7 and 8. In order to maintain the size of the sugar ring during the sequence, compound 8 was alternatively prepared from 9, by acetylation, substitution by azide and per-O-methylation. Hydrolysis of the glycoside followed by oxidation and further 5-O-methylation afforded the 6-azido-6-deoxy carboxylic
标题化合物(17)是通过两个替代序列合成的,从
D-半乳糖二
丙酮化物(1)和甲基6 - O-
甲苯磺酰基-α- D-
吡喃半
乳糖苷(9)开始。化合物1被转化为6-
溴-6-脱氧衍
生物2或被甲磺化为3。用
叠氮化
钠对2和3中的离去基团进行亲核取代,生成6-
叠氮基6-脱氧衍
生物4,在酸性条件下用
甲醇处理后,得到相应的甲基β-
呋喃糖苷(5)和α-
吡喃糖苷(6)。的游离羟基基团的甲基化5和6,得到相应的per- ø -甲基衍
生物7和8。为了在序列中维持糖环的大小,可替代地由9通过乙酰化,
叠氮化物取代和过-O-甲基化制备化合物8。糖苷
水解,然后氧化并进一步5- O-甲基化,得到6-
叠氮基-6-脱氧
羧酸16,其通过
叠氮化物官能团的氢解转化为17(从9得到的总产率为38%)。