Asymmetric Synthesis of β-Amino-α-hydroxy Aldehyde Derivatives Bearing a Quaternary Stereogenic Center

An organocatalytic approach for the stereoselective synthesis of beta-amino-alpha-hydroxy aldehydes bearing a fully substituted stereogenic center in the alpha-position with respect to the aldehyde moiety is presented. It utilizes a one-pot reaction cascade involving an aziridination reaction followed by a sodium methoxide initiated rearrangement. In order to control the chemoselectivity of the rearrangement, a new aziridinating reagent enabling the introduction of a nosyl protecting group at the nitrogen atom has been designed and introduced. Products of the reaction have thus been obtained exclusively as dimethyl acetal. The possibility to deprotect the aldehyde moiety with the preservation of the introduced optical purity has also been demonstrated.