Disclosed are compounds of Formula I: ##STR1## or a pharmaceutically acceptable salt or solvate thereof, wherein: R.sup.3 is alkyl, alkenyl, alkynyl, aryl, alkaryl, aralkyl, cycloalkyl, acyloxymethyl, alkoxy, alkoxymethyl, or alkyl substituted with cycloalkyl;R.sup.4 is H, alkyl, alkenyl, alkoxy, or --OH. Also disclosed are pharmaceutical compositions containing compounds of Formula I, methods for inhibiting tumor necrosis factor-.alpha. and methods for treating septic shock, inflammation, or allergic disease by administering a compound of Formula I.