Structural studies on bio-active compounds. Part 21. Acid-promoted debenzylations in antitumour 2,4-diamino-5-[4-(N-alkylbenzylamino)-3-nitrophenyl]-6-ethylp yrimidines.

Methylbenzoprim and ethylbenzoprim undergo debenzylation in hydrochloric acid. Two reaction mechanisms are proposed to explain this reaction, both of which involve a neighbouring group participation by the nitro group ortho to the tertiary amine fragment. The physical stability of dihydrofolate reductase inhibitors in the benzoprim class may influence the choice of a clinical candidate.