左旋薄荷醇的不对称合成

Asymmetric Synthesis of L-menthol

以4-羟基-2-丁酮和异丙叉丙酮为起始原料,经羟醛缩合、不对称氢化、羰基还原、钌催化氢化等4步反应制得左旋薄荷醇。总产率为33%,非对映体过量de值达到93%。详细探讨了铜催化剂及其用量、手性配体的选择、反应溶剂和时间等因素对胡薄荷烯酮不对称氢化反应的影响。中间体及目标化合物均通过了1H NMR、13C NMR和HRMS等技术手段的分析测定及结构表征。

L-menthol was synthesized from the starting materials of 4-hydroxy-2-butanone and mesityl oxide in four steps consisting of aldol condensation, asymmetric hydrogenation, reduction of carbonyl group, and ruthenium catalyzed hydrogenation. The total yield is 33% and the diastereomeric excess is 93%. Furthermore, the effects of copper catalysts and their loading, chiral ligands, reaction time and solvents on the asymmetric hydrogenation of piperitenone were discussed in details. The intermediates and target compound were identified and characterized by ^1H NMR, ^13C NMR and HRMS.