Highly stereocontrolled total synthesis of the polyether antibiotic salinomicin. II. Synthesis of right (C18-C30) segments from D-glucose, D-mannitol, and ethyl L-lactate.
作者:Kiyoshi HORITA、Satoshi NAGATO、Yuji OIKAWA、Osamu YONEMITSU
DOI:10.1248/cpb.37.1705
日期:——
(S)-4[(2R, 5R, 6S)-5-Ethyl-5-hydroxy-6-methyltetrahydropyran-2-yl]pentan-4-olide (5), an alkaline degradation product of salinomycin (1), was synthesized with complete stereoselectivity from D-mannitol and ethyl L-lactate.Compound 5 was then converted to (3R, 4S, 7S)-7-[(2R, 5R, 6S)]-5-ethyl-5-methoxymethoxy-6-methyltetrahydropyran-2-yl]-4, 7-bismethoxymethoxy-3-(tetrahydropyran-2-yloxy)oct-1-yne (3), a C18-C30 segment of 1, via Sharpless asymmetric epoxidation. Another C18-C30 segment, (R)-3-[2RS, 5S]-5-[(2R, 5R, 6S)-5-benzyloxy-5-ethyl-6-methyltetrahydropyran-2-yl]-2-methoxy-5-methyltetrahydrofuran-2-yl]-3-(4-methoxybenzyloxy)prop-1-yne (4), was synthesized more conveniently via coupling between a C19-C22 fragment prepared starting from D-glucose and a C23-C30 fragment prepared starting from D-mannitol and ethyl L-lactate.
(S)-4[(2R, 5R, 6S)-5-乙基-5-羟基-6-甲基四氢呋喃-2-基]戊酸内酯(5),是沙利霉素(1)的碱性降解产物,能够从D-甘露醇和乙基L-乳酸中以完全立体选择性合成。随后,将化合物5转化为(3R,4S,7S)-7-[(2R,5R,6S)]-5-乙基-5-甲氧基甲氧基-6-甲基四氢呋喃-2-基]-4,7-双甲氧基甲氧基-3-(四氢呋喃-2-氧基)辛-1-炔(3),这是1的C18-C30片段,通过Sharpless不对称环氧化反应获得。另一个C18-C30片段(R)-3-[2RS,5S]-5-[(2R,5R,6S)-5-苄氧基-5-乙基-6-甲基四氢呋喃-2-基]-2-甲氧基-5-甲基四氢呋喃-2-基]-3-(4-甲氧基苄氧基)丙-1-炔(4),则通过将一个自D-葡萄糖出发制备的C19-C22片段与一个自D-甘露醇和乙基L-乳酸出发制备的C23-C30片段结合而更方便地合成。