prov:value
| - wherein each X is independently CH, CR4, or N, e.g., selected such that no two adjacent atoms are nitrogen, provided that at least one X is N, t is 0, 1, 2, 3, 4, 5, or 6 (preferably 0, 1, 2, or 3, most preferably 0), R3 is as defined above (e.g., preferably lower alkyl, such as methyl or ethyl, preferably methyl), and A is further optionally substituted with 1-2 R3 as valence permits;
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