320. J. Graff, T. Debande, J. Praz, L. Guénée, A. Alexakis,
     “Asymmetric Bromine–Lithium Exchange: Application toward the Synthesis of Natural Product”
     Org. Lett. 2013, 15, 4270-4273.

Asymmetric bromine–lithium exchange has been successfully employed to synthesize bicoumarin chiral building blocks of (+)-isokotanin A and (−)-kotanin in good yields and with an excellent level of enantioselectivity. This is the first reported example of formal syntheses, using this direct methodology, leading to the single (M)-atropoisomer of (+)-isokotanin A and (−)-kotanin building blocks, without any resolution step.

DOI : 10.1021/ol4021157 

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