THE X-RAY CRYSTAL-STRUCTURE OF N-(1-OCTYL)-D-TALONAMIDE AND A CONSIDERATION OF ITS HYDROGEN-BONDING SCHEME

The crystal structure of N-(1-octyl)-D-talonamide [space group P2(1)2(1)2(1), a = 914.0(2), b = 581.4(1), c = 6257(l) pm] shows two independent molecules in the asymmetric unit. The oligomethylene chains of both molecules are extended. The talonic acid moieties have a gauche-bend along C-1-C-2-C-3-C-4 thereby avoiding a 1,3-syn interaction (O parallel-to O) between O-2 and O-4, whereas the resulting C parallel-to O orientation between C-1 and 0-4 is tolerated. The molecular packing is a symmetric tail-to-tail bilayer sheet comparable to that of the diastereomeric gulonamide analogue, but in contrast to the head-to-tail packing in the gluconamide analogue. This experimental result is explained by the occurrence of different hydrogen-bond patterns between hydroxyl groups (i) of adjacent crystal sheets (talon- and gulon-amide derivative) or (ii) within one crystal sheet (gluconamide derivative).