Synthesis and conformational studies on methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-hex-5-enopyranosides of the l series

Methyl 3-azido-2,3-dideoxy-α-d-xylo-, -α-d-lyxo-, and -β-d-xylo-hexopyranosides were converted into 4-O-acetyl-3-azido-6-iodo-2,3,6-trideoxy analogues via 6-O-p-tolylsulfonyl compounds. The elimination of hydrogen iodide from 6-iodo glycosides yielded methyl 4-O-acetyl-3-azido-2,3,6-trideoxy-β-l-erythro-, -α-l-threo-, and -β-l-threo-hex-5-enopyranosides. The configuration and conformation of all products are evaluated in depth on the basis of 1H and 13C NMR data. Factors determining conformational energy in 4-O-protected-3-azido-2,3,6,-trideoxy-hex-5-enopyranosides are discussed.