. . . . "R2 is H, alkyl or substituted alkyl, at least one of R1 and R2 being other than H, and each R3 is independently H, alkyl, or substituted alkyl, or two adjacent R3 moieties may be taken together to form a fused aromatic, aliphatic, or unsaturated aliphatic ring. [0053] The term alkyl, unless otherwise defined herein, refers to a straight- or branched-chain aliphatic hydrocarbon of length C1-C12, mo" .