Catalytic asymmetric total syntheses of (+)-α-cuparenone, (+)-cuparene and (+)-herbertene

Abstract

A general catalytic asymmetric route to either enantiomers of sesquiterpenes, cuparenes (1–2) and herbertenes (8–9) is disclosed from commercially available 3-methyl cyclopenten-2-one. Following a catalytic enantioselective addition of arylboronic acids to enone 15, compounds 14a-b with all carbon quaternary stereocenters are synthesized in up to 90% ee in the presence of Pd(II)-PyOx (pyridine oxazoline). Compounds 14a-b are used as precursors for the asymmetric total syntheses of (+)-cuparene (1a) (35% overall yield in 3 steps), α-(+)-cuparenone (1b) (56% overall yield in 2 steps), and (+)-herbertene (8a) (34% overall yield in 3 steps).