Structure-activity relationships of dimeric Catharanthus alkaloids. 2. Experimental antitumor activities of N-substituted deacetylvinblastine amide (vindesine) sulfates.

While structure-activity relationships for vinblastine (VLB), vincristine, deacetyl-VLB, and deacetyl-VLB amide (vindesine, VDS) in several tumor and leukemia models have been reported previously, the present study explores these relationships for a series of N-substituted vindesine analogues. These compounds were prepared from the reaction of deacetyl-VLB acid azide with the appropriate amines and were characterized by mass spectral analysis, 1H and 13C NMR spectra, electrometric titration, and infrared spectra. N-Alkylvindesines have reduced activity compared to that of VDS against the Gardner lymphosarcoma (GLS). N-beta-Hydroxyethyl-VDS surpasses vindesine in its activity against the Ridgway osteogenic sarcoma and the GLS, whereas against the B16 melanoma it is less active than VDS. N-beta-(4-Hydroxyphenethyl)-VDS, envisaged as a substrate for the enzyme tryosinase, was shown to be more active than VDS against the B16 melanoma but has only marginal activity against the GLS. In terms of collective antitumor activity against the model systems used, vindesine emerges as the congener with optimum qualities. Bis(N-ethylidenevindesine) disulfide, the first example of a bridged bisvindesine and comparable to VDS in its antitumor profile, shows evidence of activity against a P388/VCR leukemia strain known to be resistant to maytansine as well as to vincristine.