The chemical synthesis of three close analogues (2-4) of N'o-propargyl-5, 8-dideazafolate (PDDF) is described. The quinazoline ring of 2 and 4 was constructed from the pivotal intermediate 9 in a novel and unambiguous manner during the final step of the synthesis under very mild conditions. 2-Desamino-2-methyl-N'o-propargyl-5, &dideazafolate (DMPDDF)(2) was a strong inhibitor of human and Lactobacillus casei thymidylate ...