A series of novel methotrexate (MTX) derivatives (1～4) in which 4-position was substituted by 10-(p-aminobenzoyl glutamic acid) moiety of MTX and 6-position was arylated or methylated respectively were synthesized and their inhibitory activities against inducible nitric oxide synthase (iNOS) were studied. Some of them were tested for growth inhibitory activities against K562 leukemia cell simultaneously. All of them had the effect of inhibition of iNOS activity. In contrast to MTX, compounds 2 and 4 enhanced tumoricidal activity significantly. These studies show that we open up a new pathway of the structural modification of MTX, and 2-amino-4-[N-(p-aminobenzoyl glutamic acid)-yl]-6-alkyl/arylpteridine derivatives may be brought to potential antineoplastic candidates for further studies.

Key words: methotrexate derivatives, tetrahydrobiopterin, nitric oxide synthase, nitric oxide synthase inhibitor, antineoplastic