抄録
By applying enamide photocyclization, four of the representative alkaloids of hexahydrobenzo[c]phenanthridine type, which hitherto remained unexploited, have been successfully synthesized for the first time. Synthesis of Corynoline Group of Alkaloids (1), (2), and (3). The enamide (16), prepared from the 1-tetralone, was photocyclized to give the lactam (17) which was transformed into the B/C-cis-lactam (18) by reduction with NaBH_4・BF_3. Dehydrogenation with DDQ afforded the 11,12-dehydrolactam (19) which was reduced to the amine (20). Oxidation with HCO_3H afforded (±)-12-hydroxycorynoline (2) which was then subjected to hydrogenolysis to give (±)-corynoline (1). On the other hand, HCO_3H oxidation of the lactam (19) followed by LiAlH_4 reduction yielded (±)-11-epicorynoline (3). Synthesis of Chelidonine Group of Alkaloid, (±)-Homochelidonine (4). The lactam (40), which was obtained in a similar manner as above from the corresponding enamide (39), was oxidized with Pb(OAc)_4 to afford the 11,12-ortho-quinone (46) which was then reduced to give the B/C-cis-11,12-diol (47), from which (±)-homochelidonine (4) was prepared successfully.
