A novel copper-catalyzed regioselective double carbonylation of imidazo[1,2-a]pyridines with N,N-disubstituted acetamide or acetone using molecular oxygen has been described. It has provided a new approach to synthesize 1,2-carbonyl imidazo[1,2-a]pyridines, which are important substrates and intermediates in preparation of fine chemicals. The product shares a skeleton similar to that of Zolpidem, one of the most prescribed drugs in the world. (18)O-labeling experiments unambiguously established that the oxygen source of products originated from O2 rather than H2O.
An efficient copper-catalyzed selective cross coupling of imidazo[1,2-a]pyridines with methyl hetarenes has been reported. This transformation opened a new route to synthesize the C-3 carbonyl imidazo[1,2-a]pyridine derivative, which is a common structural motif in natural products and pharmaceuticals. (18)O-labeling experiments indicated that the oxygen source of products originated from O2.
Two aromatic substrates, paeonol (1) and emodin (2), were biotransformed by using transgenic crown galls of Panax quinquefolium. Four biotransformed products (3-6) were isolated and identified by physicochemical and spectral methods. A beta-glucoside (3, 73.2% of biotransformation yield) and a 1-(2,4-dimethoxyphenyl)- ethanone (4, 8.03%) were isolated from the suspension cultures after 7-day incubation of substrate 1. Upon administration of substrate 2, another beta-glucoside [emodin-6-O-beta-D: -glucopyranoside (5), 19.2%] and a hydroxylated derivative, citreorosein (6, 54.6%), were also obtained. The results demonstrate that transgenic crown galls of P. quinquefolium have the capacities to catalyze glycosylation, hydroxylation, and methylation reactions in the plant cells on those aromatic compounds.
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