IRREVERSIBLE ENZYME INHIBITORS .158. EFFECT OF BRIDGE MODIFICATION ON SELECTIVE IRREVERSIBLE INHIBITION OF DIHYDROFOLIC REDUCTASE FROM L1210 MOUSE LEUKEMIA AND LIVER BY 2,4-DIAMINO-5-(3,4-DICHLOROPHENYL)-6-[P-(M-FLUOROSULFONYLBENZAMIDOMETHYL)PHENOXYMETHYL]PYRIMIDINE .2.

The title compound (1) is an active-site-directed irreversible inhibitor of the dihydrofolic reductase from L1210 mouse leukemia that also showed specificity by its failure to inactivate this enzyme from three normal mouse tissues. However, 1 still had two shortcomings; its Ki, = 0.06 μM was considered too large to be effective in vivo and it showed poor transport through the L1210 cell wall. Thirty variants of the bridge between the pyrimidine and benzenesulfonvl fluoride moieties have now been investigated, such as (1) replacement of the oxymethyl group by thiomethyl, (CH2)2, or (CH2)4, (2) substituent effects on the phenoxy group, (3) variation of the CH2NH moiety by NH and (CH2)2NH, and (4) variation of the amide linkage by CONH, NHCONH, and SO2NH in the three previous classes. Sixteen of the compounds showed a predictable decrease in I50 = 6Ki ≤0.1 μM, but specificity was decreased or lost. The best five compounds showed inhibition of L1210 cell culture in the 0.5-1 μM range; this range is several magnitudes higher than that shown by the standard compound, 2,4-diamino-5-(3,4-dichlorophenyl)-6-methylpyrimidine (35). © 1969, American Chemical Society. All rights reserved.