| http://www.w3.org/ns/prov#value | - Z is selected from the group consisting of oxygen, sulfur, and a carbon--carbon bond, ##STR4## wherein R can be aryl (having from 6 to about 20 carbon atoms, such as phenyl) or acyl (having from 2 to about 20 carbon atoms, such as acetyl, or benzoyl), and ##STR5## wherein R1 and R2 are selected from the group consisting of hydrogen, alkyl radicals having from 1 to about 4 carbon atoms, and alkenyl
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