(4S,5R,6R)-Methyl 4-hydroxy-4,5-isopropylidenedioxy-4,5,6,7-tetrahydro-1,2,3-triazolo[1,5-a]pyridine-3-carboxylate

X-ray crystallography confirmed the structure of the title triazole, C11H15N3O5, formed from a single-step reaction of a sugar azide with a brominated ylid. The absolute configuration was determined by the use of d-ribose as the starting material. The six-membered ring is in a half-chair conformation. The crystal structure exists as chains of O—H⋯O hydrogen-bonded moleclues running parallel to the b axis.

X-ray crystallography confirmed the structure of the title triazole, C 11 H 15 N 3 O 5 , formed from a single-step reaction of a sugar azide with a brominated ylid. The absolute configuration was determined by the use of d-ribose as the starting material. The six-membered ring is in a half-chair conformation. The crystal structure exists as chains of O-HÁ Á ÁO hydrogenbonded moleclues running parallel to the b axis.
A single step synthesis (see Fig. 1) has been developed in which an azidolactol 1 was reacted with Ph 3 P=CBrCOOMe; the open chain form 2 underwent a Wittig reaction to give 3 which was followed by an intramolecular 1,3-dipolar addition of the azide to the alkene to afford 4. Subsequent elimination of HBr gave the target compound 5. The structure of the product 5, including the relative configuration of the three chiral centers was confirmed by X-ray crystallographic analysis. The absolute configuration was determined by the use of D-ribose as the starting material for the preparation of azidolactol 1.
The crystal structure of 5 exisits as chains of O-H···O hydrogen bonded moleclues lying parallel to the b-axis. Only classical hydrogen bonding has been considered. The 6-membered ring exists in a half-chair conformation.

Refinement
In the absence of significant anomalous scattering, Friedel pairs were merged and the absolute configuration was assigned from the starting material.
The relatively large ratio of minimum to maximum corrections applied in the multiscan process (1:1.21) reflect changes in the illuminated volume of the crystal. Changes in illuminated volume were kept to a minimum, and were taken into account (Görbitz, 1999) by the multi-scan inter-frame scaling (DENZO/SCALEPACK, Otwinowski & Minor, 1997).
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically.