Crystal structure and solid state 13C NMR analysis of nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-gluco- and D-galactopyranosides.

The X-ray diffraction analysis of o-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside (1), m-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside, p-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside and o-nitrophenyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside was performed. It was found that except in the case of 1, all other crystals have one molecule in the independent part of the crystal unit cell. The results support the opinion that the nitro group does not conjugate effectively with the phenyl ring. In the 13C CP MAS spectrum of 1 the signals are split, confirming the presence of two independent molecules. Similarly, the 13C CP MAS NMR spectrum of p-nitrophenyl-2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside indicated the presence of two non-equivalent molecules in the crystal unit. One of these molecules has more conformational freedom enabling rotation of the phenyl ring.