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.

No abstract

Tetrakis[(R)-3-(benzene-fused-phthalimido)-2-piperidinonate]. -The highly enantio-and diastereoselective hetero Diels-Alder reactions between the butadienes (I) and the arylpropargylaldehydes (II) or (IV) offer a straightforward entry to the cis-tetrahydropyranones (III) or (V): the yield depends strongly on the nature of the aryl substituents. Products (IIIa) and (IIIb) are converted into the target compounds (VIa) and (VIb) using standard procedures. -(WASHIO, T.; YAMAGUCHI, R.; ABE, T.; NAMBU, H.; ANADA, M.; HASHIMOTO*, S.; Tetrahedron 63 (2007) 48, 12037-12046; Fac. Pharm. Sci., Hokkaido Univ., Sapporo 060, Japan; Eng.) -Kieslich 12-221