A compound of the structure ##STR1## wherein R and R.sup.1 are each, independently, ##STR2## or hydrogen; R.sup.2 and R.sup.3 are each, independently, alkyl, arylalkyl , or R.sup.2 and R.sup.3 may be taken together to form a cycloalkyl ring;R.sup.4 is a heterocyclic N-oxide radical, which may be optionally substituted;R.sup.5 is alkyl or arylalkyl;R.sup.6 and R.sup.7 are taken together to form a saturated N-alkyl-heterocyclic N-oxide, which may be optionally substituted;k=0-1,m=0-1;n=1-6;with the proviso that R and R.sup.1 are not both hydrogen, which is useful as an immunosuppressive, antiinflammatory, antifungal, antiproliferative, and antitumor agent.