prov:value
| - In general formula I, R2 may be selected from lower alkyl, e.g., C1 -C4 alkyl, such as methyl, ethyl, propyl, n-butyl and t-butyl, and phenyl, R3 is hydrogen or methyl, w is 0 or 1, and z is a number of from 1 to 2; provided that z is 1 and R3 is hydrogen when w is 1.
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