Disclosed herein are compounds of formula II: ##STR00001## wherein Alk, Z, X.sup.1, X.sup.2, R.sup.1, --R.sup.10 and R.sup.11 are defined herein, and their salts and pharmaceutically acceptable derivatives thereof, as well as other compounds of the general formula Het-A-Alk-W-Ar-C(X.sup.2).dbd.NO-X.sup.2 where Het, A, W and Ar are also defined herein. These compounds are useful in treating picornavirus infections in mammals. Novel intermediates of these compounds, as well as pharmaceutical compositions and methods of use, are also disclosed herein.