O(CO)R6 group, and the other one is --OH or --O(CO)R6, or R1 is ???O and R2 is H; wherein R6 is a saturated or unsaturated acyclic hydrocarbon group having from 1 to about 20 carbon atoms, or --(CH2)mR7 wherein m is 0-10, and R7 is cycloalkyl radical, having from to three seven carbon atoms, or a hydrocarbyl aryl or heteroaryl, wherein the heteroatom is selected from the group consisting of nitrog