The invention provides substituted quinoxalines having the general formulas ##STR00001## where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are, inter alia, alkyl, aryl, or heteroaryl groups; Z is NH or O; and X is, inter alia, COOH or CONH.sub.2. The compounds of the invention have antiviral and immunomodulatory activity and are useful for treating infectious diseases, particularly viral infections.