Asymmetric synthesis of optically active anthracyclinone intermediate and 4-demethoxyanthracyclinones by the use of a novel chiral reducing agent.
作者:NORIHIKO TANNO、SHIRO TERASHIMA
DOI:10.1248/cpb.31.821
日期:——
Asymmetric reduction of 2-acetyl-5, 8-dimethoxy-3, 4-dihydronaphthalene (1) with a novel modified hydride, originally prepared by partial decomposition of lithium aluminum hydride with (1R, 2S)-(-)-N-methylephedrine (1.0 eq) and N-ethylaniline (2.0 eq), was found to proceed highly stereoselectively, giving (S)-(-)-2-1'-hydroxyethyl-5, 8-dimethoxy-3, 4-dihydronaphthalene ((S)-(-)-2) in 100% chemical and 92% optical yields. Direct recrystallzation of (S)-(-)-2, 92% e.e., afforded optically pure (S)-(-)-2 in 87% yield based on 1. Optically pure (S)-(-)-2 was converted to (R)-(-)-2-acetyl-5, 8-dimethoxy-1, 2, 3, 4-tetrahydro-2-naphthol ((R)-(-)-3), 100% e.e., a versatile key intermediate for optically active anthracyclinone synthesis, in a good overall yield according to the reaction scheme established in the preceding paper. Synthesis of optically pure (+)-4-demethoxydaunomycinone ((+)-4d) and (+)-4-demethoxyadramycinone ((+)-4c) was accomplished by using optically pure (R)-(-)-3 as a starting material and by following the reported synthetic scheme with slight modifications.
2-acetyl-5, 8-dimethoxy-3, 4-dihydronaphthalene (1) 与一种新型改性氢化物的不对称还原,该氢化物最初是通过氢化铝锂与 (1R, 2S)-(-)-N-methylephedrine (1. 0 eq) 和 Nethylaniline (2.0 eq) 的部分分解制备的。0 eq)和 N-乙基苯胺(2.0 eq)的部分分解反应,发现该反应具有很高的立体选择性,得到了(S)-(-)-2-1'-羟乙基-5, 8-二甲氧基-3, 4-二氢萘 ((S)-(-)-2),化学收率为 100%,光学收率为 92%。(S)-(-)-2的直接重结晶(92%)得到了光学纯度为87%的(S)-(-)-2,收率为1。根据上述论文中确定的反应方案,光学纯的 (S)-(-)-2 被转化为(R)-(-)-2-乙酰基-5, 8-二甲氧基-1, 2, 3, 4-四氢-2-萘酚((R)-(-)-3),总产率为 100%,是光学活性蒽环酮合成的通用关键中间体。以光学纯的 (R)-(-)-3 为起始原料,按照所报道的合成方案略加修改,合成了光学纯的 (+)-4-demethoxaunomycinone ((+)-4d) 和 (+)-4-demethoxyadramycinone ((+)-4c) 。