Nucleoside analogues. 13. The effect on anti-tumour activity of varying the uracil 5-substituent and the point of attachment (N1 or N3) of the uracil moiety in seco-nucleoside nitrosoureas.

The high activity against colon tumours in the mouse of nitrosoureas linked to seco-nucleosides with 5-fluorouracil or uracil as base component led us to synthesize and test similar drugs carrying other 5-substituted uracils attached by either N1 or N3. Not only were some of the new drugs active against the solid MAC 13 and against mammary and lung tumours, but unlike earlier compounds were particularly effective (especially N3 and alkoxy drugs like B.4083) against the ascitic MAC 15A, causing some cures. Further, these agents are valuable tools in the study, using modern techniques, of bifunctional alkylation of biological macromolecules, a vital principle of experimental cancer chemotherapy about which our knowledge is still very incomplete.