Abstract: Compounds of the formula: ##STR1## and stereoisomers thereof wherein X and Y, which are the same or different, are hydrogen, halogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted cycloalkylalkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted heteroaryloxy, optionally substituted arylalkoxy, optionally substituted heteroarylalkoxy, optionally substituted acyloxy, optionally substituted amino, acylamino, nitro, cyano, --CO.sub.2 R.sup.3, --CONR.sup.4 R.sup.5, or --COR.sup.6, except that X and Y are not both hydrogen; R.sup.1 and R.sup.2, which are the same or different, are alkyl or fluoroalkyl; and R.sup.3, R.sup.4, R.sup.5 and R.sup.6, which are the same or different, are hydrogen, alkyl, alkenyl, alkynyl, optionally substituted aryl, optionally substituted aralkyl, or cycloalkylalkyl.