Synthesis of pyranoisoflavones by the oxidative rearrangement of dihydropyranochalcones with thallium(III) Nitrate: Synthesis of elongatin, its angular isomer, toxicarol isoflavone, and related compounds.
作者:MASAO TSUKAYAMA、TOKUNARU HORIE、YUKIHISA IGUCHI、MITSURU NAKAYAMA
DOI:10.1248/cpb.36.592
日期:——
Elongatin, 4', 5-dihydroxy-2', 5'-dimethoxy-2", 2"-dimethylpyrano[5", 6"-g]isoflavone (1), was prepared by the oxidative rearrangement of 6'-acetoxy-2', 4-bis(benzyloxy)-2, 5-dimethoxy-2", 2"-dimethyldihydropyrano[5", 6"-c]chalcone (15) with thallium(III) nitrate and by dehy-drogenation of the resultant linear 4', 5-dihydroxy-2', 5'-dimethoxy-2", 2"-dimethyldihydropyrano-[5", 6"-g]isoflavone (19) with 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone. Its angular isomer, 4', 5-dihydroxy-2', 5'-dimethoxy-2", 2"-dimethylpyrano[6", 5"-h]isoflavone (2), was also synthesized from the corresponding chalcone (28) in a similar manner and then converted into toxicarol isoflavone (3).
Elongatin(4',5-二羟基-2',5'-二甲氧基-2",2"-二甲基吡喃[5",6"-g]异黄酮,1)是通过6'-乙酰氧基-2',4-双(苄氧基)-2,5-二甲氧基-2",2"-二甲基二氢吡喃[5",6"-c]查尔酮(15)与三氧化铊的氧化重排反应制备的。随后,通过2,3-二氯-5,6-二氰基-1,4-苯醌对得到的线性结构4',5-二羟基-2',5'-二甲氧基-2",2"-二甲基二氢吡喃-[5",6"-g]异黄酮(19)进行脱氢反应制得。其角异构体4',5-二羟基-2',5'-二甲氧基-2",2"-二甲基吡喃[6",5"-h]异黄酮(2)也以类似方式合成自相应的查尔酮(28),然后转化为毒卡烯异黄酮(3)。