The crystal structure of triacetylsphingosine.

The crystal structure of triacetylsphingosine (D-erythro-l,3-diacetoxy-2-acetamido-4-trans-octadecene, C24H43OsN) has been determined by direct methods. The crystals are orthorhombic, P212121, with a = 5.002, b = 8"709 and c = 60.62/~. Positional and isotropic thermal parameters of the non-hydrogen atoms were refined to give a final R index of 0"109. The molecules are arranged head-to-tail in layers within which the carbon chains pack according to the common orthorhombic subcell, O A.. The chain axis forms an angle of 58 ° with the end group planes. Adjacent layers show opposite tilt of the chains. In spite of the bulky acetyl branches the molecules adopt a very effective packing (Din = 1.07 g.cm-3). The molecules are connected by a continuous system of N-H--O hydrogen bonds parallel to a, and there is also evidence for two weaker C-H---O type interactions.