Irreversible Enzyme Inhibitors LXXII: Candidate Active-Site-Directed Irreversible Inhibitors of Dihydrofolic Reductase VI. Derivatives of Hydrophobically Bonded p-Alkyl and p-Aralkyl Benzoic Acids

Abstract

Since p -(bromobutyl)benzoic acid (IV), N -( m -aminobenzyl)- p -aminobenzoic acid (V), and p -benzylbenzoic acid (VI) showed good hydrophobic bonding to dihydrofolic reductase (6), four candidate active-site-directed irreversible inhibitors related to structures IV-VI were synthesized that contained a terminal alkylating function. Two of the candidates, p -(4-bromoacetamidobutyl)benzoic acid (IX) and N -( m -bromoacetamidobenzyl)- p -aminobenzoic acid (X), lost their ability to form a reversible complex with the enzyme. In contrast, α -( p -chloroacetylanilino)- p -toluic acid (XI) and α -[ p -(4-chloro-1-buten-3-one-1-yl)anilino]- p -toluic acid (XII) formed reasonably good reversible complexes with dihydrofolic reductase and could inactivate the enzyme; chloroacetone under comparable conditions showed no inactivation, thus affording strong evidence that XI and XII inactivated the enzyme via a neighboring-group reaction within a reversible complex with the enzyme.