Synthesis of N10-methyl-4-thiofolic acid and related compounds

Abstract

Compound 21 (N10-methyl-4-thiofolic acid) and related compounds were prepared as potential inhibitors of the cofactor forms of tetrahydrofolate. The preparation of 2-acetylamino-4-(benzylthio)-6-chloro-5-nitropyrimidine (4) provided an intermediate that was allowed to react with methyl p-[(3-aminoacetonyl)methylamino]benzoate oxime (16). The oxime function of the resulting 6-substituted aminopyrimidine 6 was hydrolyzed to give the corresponding acetonylaminopyrimidine 7, which on reductive cyclization gave methyl p-[[[2-amino-4-(benzylthio)-7,8-dihydro-6-pteridinyl]methyl]methylamino]benzoate (9). This dihydropteridine was oxidized with potassium permanganate, and the product was treated successively with sodium hydrosulfide to replace the benzylthio group and with aqueous sodium hydroxide to hydrolyze the ester function to give p-[[(2-amino-3,4-dihydro-4-thioxo-6-pteridinyl)methyl]methylamino]benzoic acid (N10-methyl-4-thiopteroic acid, 12). Another route to 12 involved the interaction of 2,5-diamino-4,6-dichloropyrimidine (15) with 16 to give methyl p-[[(2-amino-4-chloro-7,8-dihydro-6-pteridinyl)methyl]methylamino]benzoate (13). Displacement of the chloro group of 13 with sodium hydrosulfide followed by the simultaneous air oxidation of the dihydropteridine ring and saponification of the ester group gave 12. After protection of the 2-amino and 4-thioxo moieties of 12, the resulting intermediate benzoic acid was coupled with diethyl L-glutamate. The product of this reaction was deblocked to give 21. Methylation of 21 gave the corresponding 4-(methylthio) derivative 22, which on reaction with hydrazine gave the 4-hydrazino analog 23 of methotrexate. Reduction of 12 and 21 with sodium hydrosulfite gave the dihydropteridines 24 and 25, respectively. The title compound was an excellent inhibitor of the growth of Streptococcus faecium ATCC 8043. However, this and related compounds were ineffective inhibitors of dihydrofolic reductase and showed no significant activity in either the KB cell culture screen or against L1210 leukemia cells in mice.

1,2-Dihydropyrido[3,4-b]pyrazines: structure-activity relationships

“…Anal. (C18H21N602) C, , N. Ethyl pyrido [3,[4][5][6]pyrazine-7-carbamate (17) was prepared by hydrogenation of 34 (1.9 mmol) in EtOH (1300 mL) by a procedure similar to that described for 15. Concentration of the filtrate to one-sixth volume gave slightly impure 17: yield 405 mg (<59%); mp 209-212 °C.…”

“…Ethyl 5-Amino-3-[(jV-methyl-lV-phenylamino)methyl]pyrido [3,[4][5][6]pyrazine-7-carbamate ( 22) and 5-Amino-7-[(ethoxy carbonyl)amino]-lV-methyl-lV-phenylpyrido [3,4b ]pyrazine-3-carboxamide (28). A solution of 11 (10.5 g, 29.6 mmol)1 in acetone (500 mL) was treated dropwise with stirring with a solution of potassium permanganate in acetone (0.27%, 740 mL) until the color of permanganate persisted.…”

“…Ethyl 2,3,methyl]pyrido [3,[4][5][6]pyrazine-7-carbamate (29). A stirred suspension of 11 (100 mg, 0.267 mmol)1 in CH3CN (2 mL) under N2 was treated with NaBH3CN (45.9 mg, 0.730…”

“…These results demonstrate that the a Concentration of agent that inhibits colony formation of KB human epidermoid carcinoma cells by 50% (ref 15). 6 Lymphoid leukemia LI 210; increase in life span for the highest nontoxic dose tested (ref 15). c Toxic dose.…”

“…Dihydro-3-[(JV-methyl-JV-phenylamino)methyl]pyrido[3,[4][5][6]pyrazine-5,7-dicarbamate(15). A suspension of diethyl 4-[ [3-(N-methyl-N-phenylamino) -2-oxopropyl]amino]-3-nitro-2,6-pyridinedicarbamate hemihydrate (2.00 g, 4.14 mmol)7 in EtOH (200 mL) was hydrogenated at room temperature and atmospheric pressure over Raney nickel catalyst (~5 g) for 18 h. The solution was filtered under N2, and the filtrate was concentrated in vacuo to about half volume.…”