Structure of C-1 substituted glycopyranosyl azides: new insights based on CD measurements

CD spectra have been recorded for a series of peracetylated D-glycopyranosy l azides (D-gluco, D-galacto, D-xylo, D-arabino configuration) substituted at the anomeric position by various groups: amido, azido, cyano, ethoxy, me thoxy. Application of the azide octant rule for the interpretation of the s ign for the long-wavelength azide band allowed conformation of the azido gr oup in each mono azido derivative investigated to be established. In each I -cyano derivative, the azido group was in a gauche-like arrangement with re spect to the C-1-O-ring bond, which is considered as a manifestation of the exo-anomeric effect of the azido group. For the l-alkoxy derivatives, an a ntiparallel orientation of the azido group with respect to the C-1-O-ring b ond was found in solution by CD measurement analysis, as already observed f or methoxyazide 5 in the solid state. For azidoamide derivatives, intramole cularly (N-H-N-azide(x)) H-bonded conformers are believed to prevail in met hanol, in contrast to the situation in DMSO. (C) 1999 Elsevier Science Ltd. All rights reserved.