Reductive photocyclization of alpha-(methylthio)enamide (2) gave exclusively six-membered lactams (3) and (4) while the same reaction of alpha-(arylthio)enamides (6) and (12) was found to afford-five-membered lactams (7) and (13) as major products. A novel total synthesis of (+/-)-polyzonimine (18b) was accomplished by applying the newly found reductive photocyclization of alpha-(naphthylthio)enamide leading to the formation of five-membered lactams.
Synthesis of pyrrolizidine oximes 222 and 236: Novel alkaloids of a dendrobatid poison frog
作者:Kira D. Rutchinson、James V. Silverton、John W. Daly