Synthesis of vinca alkaloids and related compounds part 94. Epimerization of compounds with aspidospermane and D-secoaspidospermane skeleton†

The individual epimerization steps of vincadifformine (1), deethylvincadifformine isomers (2,3), their synthetic intermediates (4–13) as well as that of simpler compounds with D-secoaspidospermane skeleton (15–17) were studied a) in protic medium (boiling deuteroacetic acidic) and b) under reductive (with sodium borodeuteride in boiling acetic acid, or with sodium borohydride in boiling deuteroacetic acid) conditions.