| prov:value
| - Z is selected from the group consisting of oxygen, sulfur, ##STR6## where R is aryl (having 6 to 20 carbon atoms, such as phenyl) or acyl (having 2 to 20 carbon atoms, such acetyl, benzoyl, etc.), a carbon-to-carbon bond, or ##STR7## where R4 and R5 are independently selected from hydrogen, alkyl radicals of 1 to 4 carbon atoms, and alkenyl radicals of 2 to 4 carbon atoms;
|