The ?SuperQuat? (R)-4-phenyl-5,5-dimethyl oxazolidin-2-one as an effective chiral auxiliary for conjugate additions: Asymmetric synthesis of (?)-Aplysillamide B
作者:Stephen G. Davies、Hitesh J. Sanganee、Peter Szolcsanyi
DOI:10.1016/s0040-4020(98)01145-4
日期:1999.3
(R)-4-Phenyl-5,5-dimethyl-oxazolidin-2-one, readily available from d-phenylglycine, is shown to be an effective chiralauxiliary for stereoselective conjugate additions to attached α,β-unsaturated N-acyl moieties. Its utility is demonstrated by the asymmetric synthesis of the antifungal, antibacterial (−)-Aplysillamide B.
A catalyst system consisting of RuCl2[(S)-tolbinap][(R)-dmapen] and t-C4H9OK in 2-propanol effects asymmetric hydrogenation of arylglyoxal dialkylacetals to give the alpha-hydroxy acetals in up to 98% ee. Hydrogenation of racemic alpha-amidopropiophenones under dynamic kinetic resolution predominantly gives the syn alcohols in up to 99% ee and > 98% de, while the reaction of racemic bezoin methyl ether gives the anti alcohols in excellent stereoselectivity.