Total synthesis of phytotoxic radulanin A facilitated by the photochemical ring expansion of a 2,2-dimethylchromene in flow

• Bruce Lockett-Walters¹
• Simon Thuillier^1,2
• Emmanuel Baudouin²
• Bastien Nay*¹

• ¹Laboratoire de Synthèse Organique, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau, France
• ²Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire de Biologie du Développement, UMR7622, F-75005, Paris, France

The radulanins are biologically active bibenzyl natural products featuring a synthetically challenging 2,5-dihydro-1-benzoxepine core. In contrast with previous reports exhibiting lengthy strategies, we demonstrate the shortest synthesis of radulanin A to date, featuring a largely unexplored photochemical ring expansion reaction of a 2,2-dimethylchromene precursor. This work was adapted to a continuous-flow setup for larger-scale preparation, in view of biological investigations into the herbicidal properties of this natural product.

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