Component of the seco-iridoid and derivatives monoterpenoid indole alkaloids (MIAs, e.g. vincadifformine) biosynthesis pathway. Catalyzes the conversion of O-acetylstemmadenine (OAS) to vincadifformine. May also trigger the formation of additional unknown MIAs. dihydroprecondylocarpine acetate + NADPH = (+)-vincadifformine + acetate + NADP(+) Alkaloid biosynthesis. Belongs to the 'GDXG' lipolytic enzyme family.