OXAZOLINE-MEDIATED HIGHLY STEREOSELECTIVE SYNTHESIS OF A,B-SUBSTITUTED-B-AMINOALKANAMIDES, POTENTIAL PRECURSORS OF UNNATURAL B2,2,3-AMINO ACIDS

Abstract—The reaction of a-lithiated-2-alkyl-2-oxazolines 1-Li with aliphatic, aromatic and heteroaromatic N-cumyl nitrones results in the stereoselective formation of N-cumyl-1,6-dioxa-2,9-diazaspiro[4,4]nonanes 3 which equilibrate with the hydroxylamino derivatives 4. Such equilibrating mixtures can be easily transformed into b-amino alkanamides 5 under reductive conditions, whereas acidic hydrolysis with trifluoroacetic acid (TFA) furnishes high yields of b-phenylamino alkanamides 6 via a cumene hydroperoxide- type rearrangement. Derivatives 5 and 6 provide a backbone of potentially useful unnatural b2,2,3-amino acids.