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revised on 26.04.2019 and posted on 26.04.2019by Timothy Newhouse, Alexander Schuppe, Yizhou Zhao, Yannan Liu
We report the first total
synthesis of (+)-granatumine A, a limonoid alkaloid with PTP-1B inhibitory
activity, in 10 steps. Over the course of this study, two key methodological
advances were made: a cost effective
procedure for ketone alpha,beta-dehydrogenation using allyl-Pd catalysis, and a Pd-catalyzed protocol to
convert epoxyketones to 1,3-diketones. The central tetrasubstituted pyridine is
formed by a convergent Knoevenagel condensation and carbonyl-selective electrocyclization
cascade, which was followed by a direct transformation of a 2H-pyran to a pyridine. These studies
have led to the structural revision of two members of this family.