Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3‐hydroxy‐14′‐(3α″‐tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′‐(3α″‐tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids. Copyright © 1989 Verlag GmbH & Co. KGaA, Weinheim