Preparation of acetylenic sugar derivatives by way of 2-(N-nitroso)acetamido sugars

N-Nitrosation with dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-α-D-glucopyranose (1) and 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-galactopyranose (4) in high yield into the N-nitroso derivatives 2 and 5, respectively. Similarly, 3-acetamido-1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-glucopyranose (12) and methyl 2-acetamido-3,4,5,6-tetra-O-acetyl-2-deoxy-D-gluconate (15) gave their respective, crystalline N-nitroso derivatives 13 and 16. Various other 2-acetamido sugar derivatives were likewise nitrosated. In ethereal solution, compounds 2 and 16 reacted with potassium hydroxide in isopropyl alcohol to give the C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated as the known triacetate 3. By the same procedure, the galacto derivative 5 was converted in high yield into the 3-epimeric C₅ acetylene, 1,2-dideoxy-D-threo-pent-1-ynitol, isolated as its triacetate 6 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5-dinitrobenzoyl)-4,5-O-isopropylidene-D-threo-pent-1-ynitol (7).