Vincadifformine synthesis process

A process for the preparation of vincadifformine and substituted vincadifformines of the formula:

• ##STR6## wherein:
• R.sub.1 and R.sub.2 are the same or different and are selected from the group consisting of hydrogen, hydroxy, lower alkanoyloxy, lower alkyl carbamoyloxy, halo, lower alkyl and alkoxy groups;
• R.sub.3 is hydrogen or a lower alkyl group;
• R.sub.4 is a lower alkyl, lower hydroxyalkyl or lower alkoxyalkyl group;
• R.sub.5 is a lower alkyl group;
• the process comprising the step of condensing a carboline derivative of the formula ##STR7## wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.5 have the aforementioned meanings, with an aldehyde of the formula ##STR8## wherein X is a good leaving group selected from the group consisting of halo, benzene sulfoxy, P-toluenesulfoxy, lower alkyl or fluoralkylsulfoxy groups and R.sub.4 has the same meaning as described above, this condensation being effected in a solvent inert to the reaction conditions and at a temperature in the range of 30.degree. C. to the boiling point of the solvent.