X-ray and neutron structure of 1,8-(3,6,9-trioxaundecane-1,11-diyldioxy)-9,10-dihydro-10,10-dimethylanthracene-9-ol (P326); some pitfalls of automatic data collection.

The structure of the crown ether 1,8-(3,6,9-trioxaundecane-1,11-diyldioxy)-9,10-dihydro-10,10-dimethylanthracene-9-ol, C(24)H(30)O(6).H(2)O (1), code name P326, the parent compound for a series of derivatives, has been determined by both X-ray diffraction at room temperature and neutron diffraction at very low temperature. The unit cells are very similar at both temperatures and in both cases the crystals exhibit P2(1) symmetry with Z = 4 (two molecules, A and B, respectively, per asymmetric unit) and pseudosymmetry P2(1)/c. The higher symmetry is broken mainly by the two independent water molecules in the unit cell, some reflections which would be absent in P2(1)/c having strong intensities in both the X-ray and neutron data. In both molecules A and B hydrogen bonds involving the water molecule stabilize the macrocyclic ring structure, one involving the macrocyclic O(9) as a donor. Close contacts between the water and macrocyclic O atoms in each molecule also suggest the presence of two bifurcated hydrogen bonds, involving water HW2 to both O(16) and O(18), and water HW1 to both O(18) and O(20), respectively, with considerable variation in the geometry being present. Both molecules A and B exhibit very close pseudosymmetry across a plane perpendicular to the molecular plane and through atoms C(9) and O(18), and in addition are predominantly planar structures. The X-ray analysis failed to reveal one H atom per water molecule, each being subsequently included after location and refinement in the neutron analysis.

The stereochemical structure of disodium DL-glycerol 3-phosphate hexahydrate, the D isomer of which is an inhibitor of triose phosphate isomerase.

The stereochemistry of dl-glycerol 3-phosphate was studied by X-ray-crystallographic techniques. All the bond lengths and angles are within normally accepted limits except the ester bond, which is one of the largest yet noted, being 0.1637nm. The conformation of the molecule is such that an intramolecular hydrogen bond is formed between the hydroxyl group on the beta-carbon atom and the phosphate group. The crystal, which was grown by alcohol diffusion into an aqueous solution, is held together by sodium co-ordination and a complex system of hydrogen bonds. A table of the observed and calculated structure factors, F(obs.) and F(calc.), has been deposited as Supplementary Publication 50010 at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1972) 126, 5.