Crystal and molecular structure of methyl 4- O-methyl-β- d- ribo-hex-3-ulopyranoside

Abstract

Methyl 4- O-methyl-β- d- ribo-hex-3-ulopyranoside ( 2 ), a model compound for partially oxidized anhydroglucose units in cellulose, was crystallized from CHCl 3/ n-hexane by vapor diffusion to give colorless plates. Crystal structure determination revealed the monoclinic space group P2 1 with Z=2C 8H 14O 6 and unit cell parameters of a=8.404(2), b=4.5716(10), c=13.916(3) Å, and β=107.467(4)°. The structure was solved by direct methods and refined to R=0.0476 for 1655 reflections and 135 parameters. The hexulopyranoside occurs in a distorted chair conformation. Both hydroxyls are involved in hydrogen bonding and form zigzag bond chains along the b-axis. One of the two hydrogen bonds is bifurcated. The solid-state 13C NMR spectrum of 2 exhibits eight carbon resonances, with well-separated signals for the two methoxyls (1-OMe: 55.72 ppm, 4-OMe: 61.25 ppm) and a keto resonance with relatively large downfield shift (206.90 ppm). Differences in the C-4 and the methoxyls’ chemical shifts in the solid and liquid states were found.