The present invention relates to novel compounds, compositions comprising said compounds, and uses thereof, said compounds having the formula: ##STR00001## X is --CH.sub.2--, --O-- or --NR.sup.9--; R is a carbocyclic or heterocyclic ring; R.sup.1 is a cysteine trap; R.sup.2a, R.sup.2a', R.sup.2b, and R.sup.2b' are each independently hydrogen, C.sub.1 C.sub.4 alkyl, C.sub.1 C.sub.4 alkoxy, and mixtures thereof; or R.sup.2a' and R.sup.2b' can taken together to form a double bond; R.sup.9 is hydrogen or a unit having the formula -L.sup.2-R.sup.10; L is the same as defined herein above; R.sup.10 is hydrogen; substituted or unsubstituted C.sub.1 C.sub.6 linear; branched, or cyclic hydrocarbyl; substituted or unsubstituted aryl; substituted or unsubstituted C.sub.1 C.sub.9 heterocyclic; and substituted or unsubstituted heteroaryl.