Approaching the C<sub>33</sub>-C<sub>38</sub> Fragments of Amphotericin B and Nystatin by a Retro-[1,4]-Brook Rearrangement and the Stereoselective Manipulation of the Resulting Allylsilane
作者:Christoph Gibson、Thomas Buck、Martina Walker、Reinhard Brückner
DOI:10.1055/s-1998-1599
日期:1998.2
Sulfide S-4 (98.6% ee) furnished allylsilane S,S-anti-2 through a potassium naphthalenide induced, highly stereoselective retro-Brook rearrangement. Treatment with diethylborane followed by NaOOH/H2O2 delivered alcohol 9 as a single diastereomer. Cylization (→ 10), oxidation (→ 16), and methylation gave ketone 17. Reduction of 17 with Et3SiH in CF3CO2H was accompanied by an unprecedented rearrangement of the neighboring oxasilolane ring to the C-silylated tetrahydropyran 20. It was oxidized to alcohol 21 which - if one inverted its OH group - would become a new C33-C38 building block for the polyol/polyene antibiotics amphotericin B and nystatin.
硫化物 S-4(ee 值为 98.6%)通过萘化钾诱导的高立体选择性逆布鲁克重排反应生成了烯丙基硅烷 S,S-反-2。用二乙基硼烷处理后,再用 NaOOH/H2O2 处理,可得到单一非对映异构体的醇 9。通过酰化(→10)、氧化(→16)和甲基化得到酮 17。在 CF3CO2H 中用 Et3SiH 还原 17 时,邻近的草硅烷环发生了前所未有的重排,生成了 C 硅烷化的四氢吡喃 20。它被氧化成醇 21,如果将其羟基倒置,就会成为多元醇/聚烯抗生素两性霉素 B 和奈司他丁的新的 C33-C38 构建模块。