Abstract
Irradiation of berberinephenolbetaine (12a) and its 8-alkyl derivatives (12b-e) readily effected valence isomerization to afford the corresponding novel 8, 14-cycloberbines (13a-e) in high yields. On treatment with ethyl chloroformate, the 8, 14-cycloberbines (13a, 13b, and 13c) were efficiently converted to the spirobenzylisoquinolines (14, 15, and 16-18, respectively) via regioselective C8-N bond cleavage. The 8, 14-cycloberbine (13a), on treatment with methyl iodide, provided the benzindenoazepine (21) through regioselective C14-N bond cleavage, whereas 8-methyl- and 8-ethyl-8, 14-cycloberbine (13b and 13c) gave 8-methylidene- and (Z)-8-ethylidenespirobenzylisoquinoline (22 and 23), respectively. Irradiation of 8-methoxyberberinephenolbetaine (26) directly afforded the spirobenzylisoquinoline (31) having a ketone and a ketal on the five-membered ring. The product (31) was converted easily to a variety of spirobenzylisoquinolines such as the diketone (36), the hydroxy-ketal (38), and the keto-alcohol derivatives (41 and 42) in excellent yields.
