Compounds of formula I, II or III are provided where X1, X2 and X3 are independently selected from H and hydroxy protecting groups and R1 and R2 are independently selected from H or straight or branched chain alkyl groups having from 1 to 8 carbon atoms, straight or branched chain alkenyl groups having from 2 to 8 carbon atoms, straight or branched chain hydroxy-substituted alkyl groups having from 1 to 8 carbon atoms, or straight and branched chain hydroxy-substituted alkenyl groups having from 2 to 8 carbon atoms; and R3 is independently selected from straight or branched chain alkyl groups having from 1 to 8 carbon atoms, straight or branched chain alkenyl groups having from 2 to 8 carbon atoms, straight or branched chain hydroxy-substituted alkyl groups having from 1 to 8 carbon atoms, or straight and branched chain hydroxy-substituted alkenyl groups having from 2 to 8 carbon atoms. Such compounds are used in preparing pharmaceutical compositions and are useful in treating a variety of biological conditions.