The disclosure provides compounds of the formula I and the pharmaceutically acceptable salts thereof. The variables, e.g. R1, R2, R3, R4, A, B, J, V, W, M, J and Ar are defined herein. The disclosure also provides pharmaceutical compositions comprising a compound or salt of formula I and a pharmaceutically acceptable carrier, methods of inhibiting dihydrofolate reductase (DHFR) in vitro or in vivo with a compound or salt of formula I, and methods of treating a bacterial infections, fungal infections, and protozoal infections with a compound or salt of formula I. A compound or salt of formula I can be the first and only active ingredient used in a pharmaceutical composition or method of this disclosure or may be combined with one or more additional active ingredients that are not compounds or salts of formula I.