IRREVERSIBLE ENZYME INHIBITORS .154. SOME FACTORS IN CELL WALL TRANSPORT OF ACTIVE-SITE-DIRECTED IRREVERSIBLE INHIBITORS OF DIHYDROFOLIC REDUCTASE DERIVED FROM 5-SUBSTITUTED 2,4-DIAMINOPYRIMIDINES

5-[p-(m-fluorosulfonylbenzamido)phenoxypropyl]-2,4,6-triaminopyrimidine (1a) was previously observed lo be an isozyme-specific active-site-directed irreversible inhibitor of dihydrofolic reductase from L1210 mouse leukemia that showed no irreversible inhibition of the enzyme from normal mouse liver; however, 1a was ineffective in vivo due to poor penetration of the L1210 cell wall. Replacement of the ether bridge of 1a by thiocther (2) or methylene (3) gave irreversible inhibitors of similar isozyme specificity that could operate at much lower concentration due to their better reversible binding than 1a: cell wall transport was not improved with 2 or 3. This difficulty in cell wall transport of 1a, 2, and 3 compared to 2,4-diaimno-5-(3,4-dichlorophenyl)-(5-methylpyrimidine (5) was traced to two factors: (a) replacement of the 3,4-dichlorophenyl group of 5 by phenylbutyl (7) or p-aminophenoxypropyl (6) was extremely detrimental to transport, and (b) further smaller losses in transport occurred when 6 or 7 were converted to the m-fluorosulfonylbenzamido type of irreversible inhibitor (1b, 8). In contrast to 7, 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-phenylbutyl-2-triazme (16) was transported as well as 5. © 1969, American Chemical Society. All rights reserved.