Biotransformation of ajmaline in plant cell cultures of Rauwolfia serpentina Benth.: the new indole alkaloids raumacline and N(β)-methyl-raumacline - Polz,L.; Stöckigt,J.; Takayama,H.; Ushida,N.; Aimi,N.; Sakai,S.-I. (Tetrahedron Letters, 1990)