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.

(24R)-24,25-Dihydroxycycloartan-3-one.

In the title compound, C(30)H(50)O(3), the three six-membered rings adopt chair, twist and twist-boat conformations. The five-membered ring is in a slightly distorted envelope conformation. The substituent on the five-membered ring is in an extended conformation, with its two hydroxyl O atoms forming an intramolecular hydrogen bond. One of these O atoms also forms an intermolecular hydrogen bond with the oxygen of the carbonyl group in a neighbouring molecule.

A double mesogen based on linked p-terphenyl units.

The structure of bis(4,4"-decyloxy-p-terphenyl-2'-ylmethyl) carbonate, C(79)H(110)O(7), (I), has been determined at 123 K. It is a new type of twin mesogen. No two adjacent aromatic rings are coplanar and the four decyloxy side chains are maximally extended. Molecules of the compound are packed along the crystallographic a axis. The molecular arrangement is a precursor of a smectic A phase.

Neurothekeoma of Gallager and Helwig (dermal nerve sheath myxoma variant): report of a case with electron microscopic and immunohistochemical studies.

A patient presented with a frontal nodule of the scalp. Histopathological examination revealed a myxomatous multilobulate tumor composed of epithelioid cells with variable pleomorphism. Perineurium-like structures were seen but only around isolated lobules located at the tumor periphery. Electron microscopy revealed polygonal cells and cells with elongated cytoplasmic processes. Many cells had myelinoid figures. A basement membrane-like lamina was noted around some cells. Some of the tumor cells were immunoreactive for myelin basic protein. This finding suggests that the tumor cells are of schwannian type. Neurothekeoma of Gallager and Helwig is a rare, probably benign tumor with fairly distinctive histopathologic characteristics. It appears to be a variant of dermal nerve-sheath myxoma.