Two series of selective inhibitors of herpes simplex virus types 1 and 2 (HSV1, 2) thymidine kinases (TK) have been developed as potential treatment of recurrent virus infections. Among compounds related to the potent base analog W-[m-(trifluoromethyl) phenyl] guanine (mCF3-PG), none was a more potent inhibitor than mCF3PG itself. Compounds related to the nucleoside W-phenyl-2'-deoxyguanosine (PhdG), but with alkyl, hydroxyalkyl, and ...