Stereoselective nucleophilic formylation and cyanation of α-alkoxy- and α-aminoaldehydes

The spontaneous 1,2-addition of formaldehyde NN-dialkylhydrazones to carbohydrate-derived alpha -alkoxyaldehydes takes place under neutral conditions and in the absence of catalysts or promoters to afford the corresponding (alpha -hydroxyhydrazones in good to excellent yields and with highly anti diastereoselectivities. Subsequent transformations of the hydrazono group into aldehydes and nitriles following known procedures provide a new entry into the homologation of carbohydrates and the synthesis of cyanohydrins, respectively. Additionally, reaction of methyleneaminopyrrolidine with N-Boc-protected (alpha -aminoaldehydes from natural amino acids efficiently affords the corresponding adducts under the same conditions. From these adducts, a variety of biologically interesting (alpha -hydroxy-beta -aminocarbonyl compounds can be accessed upon manipulation of the hydrazone moiety.