A molecular conjugate is provided having the formula: ##STR00001## wherein R.sub.1 is a de-hydroxyl or de-amino moiety respectively of a hydroxyl-bearing or amino-bearing biologically active molecule or an analog or derivative thereof, and Z is --O-- or --NH--, respectively, Y is a straight or branched alkyl having 1 to 20 carbons that may be optionally substituted with one or more phenyl, a cycloalkyl optionally substituted with one or more alkyl or phenyl, or an aromatic group optionally substituted with one or more alkyl groups, electron-withdrawing groups, or electron-donating groups; and R.sub.2 is --CH.dbd.CH(W), --CH(OH)CH(OH)W, or --C(O)H, where W can be H, a straight or branched alkyl having 1 to 20 carbons that may be optionally substituted with one or more phenyl, a cycloalkyl optionally substituted with one or more alkyl or phenyl, or an aromatic group optionally substituted with one or more alkyl groups, electron-withdrawing groups, or electron-donating groups.