Six-Step Syntheses of (−)-1-Deoxyaltronojirimycin and (+)-1-Deoxymannonojirimycin from <i>N</i>‑<i>Z</i>‑<i>O</i>‑TBDPS‑l‑serinal

Highly stereoselective six-step syntheses of (−)-1-deoxyaltronojirimycin (<i>altro</i>-DNJ) and (+)-1-deoxymannojirimycin (<i>manno</i>-DNJ) from <i>N</i>-Cbz-<i>O</i>-TBDPS-l-serinal are described. Key transformations involve a two-step preparation of a functionalized dihydropyridin-3-one as a common intermediate followed by Luche reduction and dihydroxylation (for <i>altro</i>-DNJ). The same sequence employing an epoxidation/epoxide opening in place of dihydroxylation furnishes <i>manno</i>-DNJ