Synthesis of α^2,2,β³-diamino acids by double stereodifferentiation aldol addition of oxazolidinone enolates to N-(tert-butylsulfinyl) imines

A novel application of Seebach's "SRS" synthetic principle works efficiently when conformationally restrained trisubstituted chiral α^2,2,β³-diamino acids are synthesized by double stereoinduction reactions of chiral oxazolidinone enolates with N-sulfinyl aldimines. Two stereoisomers were isolated in a form of 1′-(sulfinylamino) oxazolidinones and bicyclic 1H,3H-imidazo[1,5-c]oxazole-1,5(6H)-diones, from which the α^2,2,β³-diamino acids are obtained by selective deprotection methodologies. Among a variety of highly functionalized diamino acids, this highly diastereoselective protocol provides a synthetic route for yet unreported C-glycosyl and α-nucleoside diamino acids.