Synthesis of 2-Deoxy-2-<i>C</i>-alkyl Glycal and Glycopyranosides from 2-Hydroxy Glycal Ester

A method to convert 2-hydroxy glycal ester to the corresponding 2-deoxy-2-<i>C</i>-alkyl glycal in a facile manner, through key reactions including (i) <i>C</i>-allylation at <i>C</i>-1, (ii) Wittig reaction, and (iii) Cope rearrangement of a 1,5-diene derivative, is reported. The α-anomer of the 1,5-diene derivative underwent Cope rearrangement to afford 2-deoxy-2-<i>C</i>-glycal derivative, whereas the β-anomer was found to be unreactive. Employing this sequence, 3,4,6-tri-<i>O</i>-benzyl-2-<i>O</i>-acetyl-1,5-anhydro-d-<i>arabino</i>-hex-1-enitol was transformed to 3,4,6-tri-<i>O</i>-benzyl-2-deoxy-2-<i>C</i>-alkyl-1,5-anhydro-d-<i>arabino</i>-hex-1-enitol. 2-Deoxy-2-<i>C</i>-alkyl glycal derivative is a suitable glycosyl donor to prepare 2-deoxy-2-<i>C</i>-alkyl glycosides, mediated through haloglycosylation and a subsequent dehalogenation. A number of 2-deoxy-2-<i>C</i>-alkyl glycosides, with both glycosyl and nonglycosyl moieties at the reducing end, are thus prepared from the glycal