Manipulation of cis (4S,5S)-4,5-disubstituted 2-oxazolidinones (4, 5), derived easily from D-glucosamine (1) as a chiral pool, including degradation of the C6-carbon and/or one-carbon homologation at the C1-position allowed chiral syntheses of (2S,3S)-dihydroxy-(4S)-amino acid moieties (6-8), which are important structural components of a gastroprotective substance, AI-77-B, and a group of antitumor substances, calyculins.