The physiological parameters for application experiments using immature seeds of Colchicum autumnale were optimized, so that incorporation rates in the range of 10% and higher were consistently obtained with intermediate precursors. Application of tritium and 13C-labelled phenethylisoquinolines showed that N-methylation occurs prior to the substitution of ring C and that the free hydroxy group in position 13 of autumnaline is ...
