Crystal structure and NMR spectroscopy of aldonamides derived from D-glycero-D-gulo-heptono-1,4-lactone.

We report the preparation of 12 aldonamides derived from D-glycero-D-gulo-heptono-1,4-lactone, their NMR characterization and study (13C, 1H, 15N NMR) in Me2SO-d6 solution. The evaluation of the coupling constants 3JH,H has shown that the sugar chain conformation in solution is all-trans for the studied amides. Because some amides crystallized, we discussed the crystal packing and found motifs. The conformation of the amides in the crystal structures displays two sickles at C2 and C3, with the exception of one that is all-trans. The bends cause the formation of the mean planes C1-C2-C3 and C3-C4-C5-C6-C7 with an average interplanar angle of 88 degrees. We found three main kinds of crystal packing depending on the N-substituent; head-to-tail, bilayer and pseudo-hexagonal mode, all the three show hydrogen-bonding networks that stabilize the crystal lattice.