Enantioselective Synthesis of (+)-Providencin and Its Unexpected Regioisomer via a Biomimetic Norrish–Yang Cyclization from (−)-Bipinnatin E

• DOI: 10.1021/acs.orglett.3c03604
• Publication Date: 2023-12-14T23:27:45Z
• Authors: Paul D. Scesa; Stéphane P. Roche; Lyndon West
• Keywords: Structural isomer; Absolute Configuration

A biomimetic semisynthesis of the diterpenoid (+)-providencin (2) and unexpected novel C14 regioisomer 3 was achieved by photoirradiation proposed biosynthetic cembranoid precursor (−)-bipinnatin E (1). The absolute configuration assignments 1 2 correlation were established X-ray analysis. combination NOESY data photochemical reaction results revealed that both C2 positions macrocycle (−)-1 are suitable for hydrogen abstraction, thus affording an explanation to mixture cyclobutane photoproduct isomers obtained a Norrish–Yang cyclization. These also support hypothesis describing genuine transformation into (+)-2, without refuting products 2/3 might be artifacts isolation.