Ruthenium-Catalyzed Asymmetric N-Demethylative Rearrangement of Isoxazolidines and Its Application in the Asymmetric Total Syntheses of (-)-(1R,3S)-HPA-12 and (+)-(1S,3R)-HPA-12

An asymmetric N-demethylative rearrangement of 1,2-isoxazolidines catalyzed by ruthenium is described. Enantioenriched syn-1,3-aminoalcohols as well as cis-1,3-oxazinanes, which are useful building blocks, can be efficiently prepared stereospecifically by this reaction in good yields, via the isoxazolidine intermediates in situ generated from a nitrone bearing a chiral auxiliary and styrenes. This asymmetric reaction was also applied in the asymmetric total syntheses of both (-)-(1R,3S)-HPA-12 and (+)-(1S,3R)-HPA-12.