Expeditious synthesis of enantiopure, orthogonally protected bis-α-amino acids (OPBAAs) and their use in a study of Nod1 stimulation.

A convenient approach towards the synthesis of orthogonally protected chiral bis-α-amino acids (OPBAAs) is described. The key transformations include: (1) a highly stereoselective conjugation (alkylation) of the Schöllkopf bis-lactim ethers and oxazolidinyl alkyl halides to build a backbone skeleton; and (2) our orthogonal protection strategy. A series of enantiopure OPBAAs bearing a variety of alkyl chain as a spacer; two stereogenic centers; and three protecting groups were prepared as examples.