Synthesis of Naturally Occurring Prenylated Benzophenones. Vismiaphenone A, Vismiaphenone B, and Isovismiaphenone B
作者:Ved Prakash Pathak、Rajinder Nath Khanna
DOI:10.1246/bcsj.55.2264
日期:1982.7
2,4,6-Trihydroxybenzophenone on prenylation with 2-methyl-3-buten-2-ol in the presence of (C2H5)2O·BF3 yielded 2,4,6-trihydroxy-3,5-diprenylbenzophenone (3), 2,6-dihydroxy-4-prenyloxybenzophenone, 2,6-dihydroxy-3-prenyl-4-prenyloxybenzophenone, a benzodipyran and 6-benzoyl-5,7-dihydroxy-2,2-dimethyl-3-prenylchroman. 3 on reaction with 2 moles of p-toluenesulfonyl chloride followed by methylation and detosylation gave a naturally occurring benzophenone, vismiaphenone A (12). Cyclodehydrogenation of 6-hydroxy-3,5-diprenyl-2,4-ditosyloxybenzophenone gave 8-benzoyl-2,2-dimethyl-6-prenyl-5,7-ditosyloxy-2H-1-benzopyran, which on detosylation gave another naturally occurring benzophenone, isovismiaphenone B, while cyclodehydrogenation of 3 gave vismiaphenone B, another naturally occurring benzophenone. 2,4-Dihydroxy-6-methoxy-benzophenone on similar treatment with 2-methyl-3-buten-2-ol afforded 12 directly.
2,4,6-三羟基二苯甲酮与2-甲基-3-丁烯-2-醇在(C2H5)2O·BF3存在下进行苄基化反应,生成2,4,6-三羟基-3,5-二苄基二苯甲酮(3)、2,6-二羟基-4-苄氧基二苯甲酮、2,6-二羟基-3-苄基-4-苄氧基二苯甲酮、苯并二吡喃和6-苯甲酰基-5,7-二羟基-2,2-二甲基-3-苄基苯并二氢吡喃。3与2摩尔对甲苯磺酰氯反应,然后甲基化和脱甲酰化,生成天然存在的二苯甲酮,即维西米阿苯甲酮A(12)。6-羟基-3,5-二苄基-2,4-二甲酰氧基二苯甲酮的环脱氢反应生成8-苯甲酰基-2,2-二甲基-6-苄基-5,7-二甲酰氧基-2H-1-苯并吡喃,脱甲酰