A compound of the structure ##STR1## wherein R.sup.1 is ##STR2## R.sup.2 is hydrogen, alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, or Ar;R.sup.3 is hydrogen, alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, or --CO.sub.2 R.sup.8 ;R.sup.4 is alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, Ar, aminoalkyl, thioalkyl, alkylthioalkyl, hydroxyalkyl, or --CO.sub.2 R.sup.8 ;R.sup.5 is hydrogen, alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, At, or --CO.sub.2 R.sup.8 ;R.sup.6 is hydrogen, alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, or Ar;R.sup.7 is alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, or Ar;R.sup.8 is hydrogen, alkyl, alkenyl, alkynyl, trifluoromethyl, arylalkyl, fluorenylmethyl, orAr;Y is O or S;X is .dbd.N--O--(CH.sub.2).sub.f --Z or .dbd.N--O--Ar;Z is hydrogen, alkenyl, alkynyl, alkoxy, cyano, fluoro, trifluoromethyl, --NR.sup.5 R.sup.6, aryloxy, or Ar;Ar is aryl which may be optionally mono-, di-, or tri- substituted;a=0-4;b=0-1;c=0-4;d=0-6;e=0-6; andf=0-6;or a pharmaceutically acceptable salt thereof, with the proviso that when f is 0, Z is hydrogen and further provided that when R.sup.3 or R.sup.5 is --CO.sub.2 R.sup.8, R.sup.8 is not hydrogen which is useful as an immunosuppressive, antiinflammatory, antifungal, antiproliferative, and antitumor agent.