Total Synthesis of the Proposed Structure of Turkiyenine

The secondary metabolite, turkiyenine, is a probable bioactive component of the medicinal plant, Hypecoum procumbens L. Structurally, it is an isoquinoline-derived alkaloid composed of dihydrobenzofuran and 3-benzazepine-1-one moieties arranged in a unique spirocyclic structure. Yet despite the intriguing structure and medicinal relevance of benzofuran and benzazepine motifs, neither a synthetic study nor a biological evaluation of turkiyenine have been reported to date. Herein we communicate the first total synthesis of the proposed structure of turkiyenine, and on the basis of X-ray crystallography show that the proposed structure is incorrect. The key steps of our synthesis include an aza-spiro annulation onto a benzofuran using a rhodium-nitrenoid to construct a 3-alkyl-3-amino-2,3-dihydrobenzofuran, an acyl-alkylation of an aryne onto a beta-ketolactam to form a 3-benzazepine-1-one, and chemoselective reduction of an amide in the presence of a ketone.