Total synthesis of indole and dihydroindole alkaloids. XVII. The total synthesis of catharine and vinamidine (catharinine)

Oxidation of 16,18-dicarbomethoxycleavamine gave the epoxide (6) and the enamide (9). Similar oxidation of 3′,4′-dehydrovinblastine (8) or leurosine (7) gave the natural product catharine (3). Potassium permanganate oxidation of 7 or 8 gave 3R-hydroxyvinamidine (19) whereas similar oxidation of 4′-deoxyleurosidine (29) gave the alkaloid vinamidine (4).