Synthesis of N-Bz-Protected D-Daunosamine and D-Ristosamine by Silica Gel Promoted Intramolecular Conjugate Addition of Trichloroacetimidates obtained from Osmundalactone and Its Epimer

Trichloroacetimidates prepared from osmundalactone and its epimer unexpectedly undergo intramolecular conjugate addition during silica gel chromatography to produce oxazolines in excellent yields. The novel, simple synthesis of N‐Bz‐protected D‐daunosamine and D‐ristosamine from these oxazolines is described in this paper. Trichloroacetimidates, which are prepared from osmundalactone and its epimer, unexpectedly undergo silica gel promoted stereoselective intramolecular conjugate addition to produce the oxazolines in excellent yields. The novel, simple synthesis of N‐Bz‐protected D‐daunosamine and D‐ristosamine from these oxazolines is described.