Asymmetric syntheses of diarylheptanoid natural products (−)-centrolobine and (−)-de- O-methylcentrolobine via hetero-Diels–Alder reaction catalyzed by dirhodium(II) tetrakis[( R)-3-(benzene-fused-phthalimido)-2-piperidinonate

Abstract

Catalytic asymmetric syntheses of (−)-centrolobine and (−)-de- O-methylcentrolobine have been achieved, incorporating a hetero-Diels–Alder (HDA) reaction between 4-aryl-2-silyloxy-1,3-butadienes and phenylpropargyl aldehyde derivatives as a key step. The HDA reaction using dirhodium(II) tetrakis[( R)-3-(benzene-fused-phthalimido)-2-piperidinonate], Rh 2( R-BPTPI) 4, as a chiral Lewis acid catalyst provides exclusively cis-2,6-disubstituted tetrahydropyran-4-ones in up to 93% ee.