Preferably, R1 is a linear or branched alkyl or linear or branched alkenyl group having from about 8 to about 30 carbon atoms or ???R3OR4, R2 is hydrogen, a linear or branched alkyl or linear or branched alkenyl group having from 1 to about 30 carbon atoms, R3 is a linear or branched alkylene or alkenylene group having from 2 to about 6 carbon atoms, R4 is a linear or branched alkyl or alkenyl gro