Asymmetric hydrogenation of alpha-primary and secondary amino ketones: efficient asymmetric syntheses of (-)-arbutamine and (-)-denopamine.

Two beta-receptor agonists (-)-denopamine and (-)-arbutamine were prepared in good yields and enantioselectivities by asymmetric hydrogenation of unprotected amino ketones for the first time by using Rh catalysts bearing electron-donating phosphine ligands. A series of alpha-primary and secondary amino ketones were synthesized and hydrogenated to produce various 1,2-amino alcohols in good yields and with good enantioselectivies. This Rh electron-donating phosphine-catalyzed asymmetric hyderogenation represents one of the most promising and convenient approaches towards the asymmetric synthesis of chiral amino alcohols.