A strategy for selective mono-, di- and tri-O-methylation of kaempferol, predominantly on the basis of selective benzylation and controllable deacetylation of kaempferol acetates, was developed. From the selective deacetylation and benzylation of kaempferol tetraacetate (1), 3,4′,5,-tri-O-acetylkaempferol (2) and 7-O-benzyl-3,4′5,-tri-O-acetylkaempferol (8) were obtained, respectively. By controllable deacetylation and followed selective or direct methylation of these two intermediates, eight O-methylated kaempferols were prepared with 51–77% total yields from kaempferol.
开发了一种选择性对卡培菲醇进行单甲基化、二甲基化和三甲基化的策略,主要基于对卡培菲醇醋酸酯的选择性苄基化和可控的去乙酰化。通过对卡培菲醇四乙酰酸酯(1)的选择性去乙酰化和苄基化,分别得到了3,4′,5-三乙酰卡培菲醇(2)和7-苄基-3,4′5-三乙酰卡培菲醇(8)。通过可控的去乙酰化,然后对这两种中间体进行选择性或直接的甲基化,从卡培菲醇中总产率为51-77%制备了八种甲基化卡培菲醇。