The Structure and Stereochemistry of Gabosine K: Syntheses of 7-O-Acetylstreptol and 7-O-Acetyl-1-epi-streptol
作者:Tony Shing、Hau Cheng
DOI:10.1055/s-0029-1218540
日期:2010.1
Gabosine K, whose structure was erroneously assigned previously as 7-O-acetyl-4-epi-streptol, has been synthesized for the first time from d-glucose via a key carbocyclization strategy, intramolecular direct aldol reaction of a 2,6-diketone, in 15 steps with 13.5% overall yield. In the same manner, (+)-7-O-acetyl-streptol has been constructed for NMR spectral comparison. The structure, relative and absolute configurations of (-)-gabosine K are now revised and established as (-)-7-O-acetyl-1-epi-streptol, that is, (1R,2S,3S,4R)-tetrahydroxy-5-acetoxymethylcyclohex-5-ene. Since the specific rotation of the natural product is not available, the absolute configuration of natural gabosine K is either (-)-7-O-acetyl-1-epi-streptol or its enantiomer.
Gabosine K 的结构以前被错误地归类为 7-O-acetyl-4-epi-streptol ,该化合物是通过一种关键的碳环化策略--2,6-二酮的分子内直接醛醇反应--首次从 d-葡萄糖中合成的,共经过 15 个步骤,总收率为 13.5%。以同样的方式,还构建了 (+)-7-O- 乙酰基链烷醇,用于核磁共振光谱比较。(-)-gabosine K 的结构、相对构型和绝对构型现已修订并确定为 (-)-7-O-乙酰基-1-epi-链醇,即 (1R,2S,3S,4R)-四羟基-5-乙酰氧甲基环己-5-烯。由于无法获得天然产物的特定旋转,因此天然棉子碱 K 的绝对构型是 (-)-7-O- 乙酰基-1-epi-链醇或其对映体。