CRYSTAL-STRUCTURE AND MOLECULAR MECHANICS ANALYSIS OF METHYL 6-O-(N-HEPTYLCARBAMOYL)-ALPHA-D-GLUCOPYRANOSIDE (HECAMEG)

The crystal structure of methyl 6-O-(N-heptylcarbamoyl)-alpha-D-glucop yranoside (trivial name: HECAMEG), C15H29NO7, was determined using MoK alpha X-ray data at 110 K. The space group is P2(1)2(1)2(1), with fou r molecules in a unit cell having dimensions of a = 5.070 (5), b = 8.2 82 (4), and c = 43.16 (2) Angstrom. Because all the crystals which cou ld be grown were twinned, a high-resolution data set could not be coll ected. Consequently, a highly refined structure could not be reached. Therefore, the crystalline structure was submitted to a further refine ment based on optimization of both intramolecular and intermolecular i nteractions using molecular mechanics methods. The present work provid es structural information about the fairly uncommon carbamoyl group, a s well as on the amphiphilic components of HECAMEG. A C-4(1) conformat ion is maintained for the glucopyranoside, and the orientation around C-5-C-6 is gauche-gauche; the polymethylene chain is observed in its f ully extended, all anti conformation. Whereas there is no intramolecul ar hydrogen bonding, three intermolecular H bonds are observed. One in volves the N-H of the carbamoyl group linked to the carbonyl oxygen of a neighboring group. The two others link the secondary hydroxyl group s of the glucopyranose through a network which propagates along one of the 2(1) screw axis. A complete analysis of the intermolecular arrang ement has been performed, which yields a detailed analysis of the crys tal packing. To the best of our knowledge this is the first amphiphili c carbohydrate structure which crystallizes in a bilayer type of arran gement not having interdigitized hydrophobic acyl chains.