In 2010 the structure of the compound (+)-trigonoliimine A

Chapter 5, Problem 5.66

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In 2010 the structure of the compound (+)-trigonoliimine A (isolated from the leaves of a plant in the Yunnan province of China) was reported as shown below. In 2011, a synthesis of the reported structure was accomplished, and the configuration of a chirality center in the compound was found to have been incorrectly assigned in 2010 (J. Am. Chem. Soc. 2011, 133, 1076810771): N N N N OMe Reported structure of (+)-trigonoliimine A H (a) Draw the correct structure of (+)-trigonoliimine A and provide its absolute stereochemical configuration. (b) The 2011 synthesis enabled the investigators to determine that the original assignment of configuration (of the natural product) was incorrect. Explain how this determination could have been made.