Oxazine formation by MsCl/Et3N as a convenient tool for the stereochemical interconversion of the hydroxyl group in N-acetyl 1,3-aminoalcohols. Asymmetric synthesis of N-acetyl l-xylo- and l-arabino-phytosphingosines

Use of MsCl/Et3N was proven to provide a convenient synthetic tool for the stereochemical intercoversion of the hydroxyl group in N-acetyl 1,3-aminoalcohols. Thus, under these conditions, the alcohols 4 and 6 smoothly converted to the oxazines 5 and 7, respectively, which were hydrolyzed to generate the corresponding inverted alcohols 6 and 4 in one pot. Further elaboration of 4 and 6 led to the efficient asymmetric synthesis of N-acetyl l-xylo- and l-arabino-phytosphingosines (11 and 15), respectively, via olefin cross metathesis reactions.