A Practical and Scalable-Oriented Enantioselective Synthesis of (S)‑Autumnaline
Alessandro Brusa1, Matteo Bottiglieri2, Carola Tomassi1
1Department of Physical and Chemical Sciences, Consorzio C.I.N.M.P.I.S., INSTM RU, Università degli Studi dell'Aquila, L'Aquila 67100, Italy.
Abstract:
A process-friendly and enantioselective total synthesis of (S)-autumnaline, a key biosynthetic precursor to the colchicine alkaloids, is reported. The strategy relies on a Bischler-Napieralski cyclization-asymmetric imine reduction sequence to construct the chiral isoquinoline core. Significant process innovations include a cyanide-free homologation using a Darzens reaction and a chromatography-free purification strategy via d-tartrate salt formation. The absolute configuration was definitively confirmed through a combination of circular dichroism (CD) spectroscopy and computational modeling. This developed process affords (S)-autumnaline in 11 steps (nine-step longest linear sequence) with a 13% overall yield.
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