Christopher J. Gilmore

A quantitative study of the aluminium trichloride–acetonitrile system using X-ray crystallography, electrical conductivity, aluminium-27 and chlorine-35 nuclear magnetic resonance and Raman spectroscopy. The characterization of the pentakis(acetonitrile)chloroaluminium(III) ion in the solid state and in solution

The compounds MCl3(M = Al, Ga, or In) yield electrically conducting solutions in acetonitrile. Boron trichloride gives non-conducting solutions and, contrary to previous work, this is interpreted as due to the presence of a molecular solute BCl3·MeCN. The electrical-conductivity data for AlCl3 in acetonitrile are discussed in detail and it is shown that from the results obtained it is not possible to differentiate between 1 : 1 and 1 : 2 electrolyte behaviour. Quantitative Raman and 27Al n.m.r. spectra demonstrate that ca. 70% of the aluminium in solutions of AlCl3 in acetonitrile is present in the form of [AlCl4]–. An X-ray single-crystal study of the solid adduct AlCl3·2MeCN crystallizing from such a solution shows that this adduct is correctly formulated as the auto-complex [AlCl(NCMe)5]2+2[AlCl4]–·MeCN. Further 27Al n.m.r. studies on solutions of Al[ClO4]3 in acetonitrile and of the solute AlCl[ClO4]2, in conjunction with the work on AlCl3 demonstrate that [AlCl(NCMe)5]2+ is the major cationic constituent of aluminium trichloride solutions in acetonitrile. The electrical-conductivity, Raman, and n.m.r. data on these solutions are all satisfactorily interpreted by the principal ionization scheme [AlCl(NCMe)5]2+2[AlCl4]– which is the formulation found for the crystal. The ionization of AlCl3, but the non-ionization of BCl3, in solution in acetonitrile is attributed principally to the ability of aluminium to adopt a co-ordination number of greater than four in ions such as [AlCl(NCMe)5]2+.

X-Ray crystal and molecular structure of acetylcolletotrichin (colletotrichin), a metabolite of Colletotrichum capsici

From X-ray crystallographic data, the structure and relative stereochemistry is deduced for acetylcolletotrichin, a previously described metabolite of Colletotrichum capsici; since the metabolite does not contain an acetyl group, it is proposed that the name be changed to colletorichin.

Crystal and molecular structure and absolute configuration of maytansine (3-bromopropyl) ether

The molecular structure and absolute configuration of maytansine (Ia) have been found from a three-dimensional single-crystal X-ray analysis of its (3-bromopropyl) ether (Ib). Crystals are orthorhombic, space group P212121 with a= 24·239(4), b= 16·044(4), c= 10·415(2)A, and Z= 4. The structure was solved by the heavy-atom method and refined by Fourier and least-squares methods to R 0·101 for 927 independent reflections measured by counter diffractometry. The absolute configuration was established by the anomalous dispersion method.The molecule contains a 19-membered ring with the nitrogen-containing aliphatic portion bridging a substituted phenyl group in a 1,3-ansa-fashion. The structure shows similarities to those of the ansamycin antibiotics, but has novel epoxide, carbinolamine ether, and aryl halide functions.

Fungal products. Part 22. X-Ray and molecular structure of the mono-acetate of colletotrichin

The structure and relative stereochemistry (1) for colletotrichin, a metabolite of Colletotrichum capsici, previously isolated under the name acetylcolletotrichin, is deduced from an X-ray crystallographic study of the mono-acetate (2). The crystals are orthorhombic P212121, a= 16.370(12), b= 11.919(3), c= 15.506(9)A, Z= 4. Using 1 554 independent ‘observed’ intensities, the refinement converged to R 0.058 (R′ 0.074). The metabolite consists of a tetra-substituted γ-pyrone, containing all non-hydroxylic oxygens, and linked to an unusual bicyclic terpene.

Eriolangin and eriolanin, novel antileukaemic seco-eudesmanolides from Eriophyllum lanatum

The isolation and structural elucidation of eriolangin (1) and eriolanin (2), novel antileukaemic 1,10-seco-eudesmanolides from Eriophyllum lanatum, are reported.

X-Ray crystal structure of the 1 : 2 adduct of aluminium trichloride with acetonitrile; an interesting example of auto-complex formation

Single crystal X-ray studies have shown that the co-ordination complex of aluminium trichloride with acetonitrile of stoicheiometry AlCl3–2MeCN has the ionic structure [AlCl(MeCN)5]2+[AlCl4]2– and contains one molecule of solvent acetonitrile per asymmetric unit.

Crystal and molecular structures and absolute configuration of triptolide and tripdiolide, two anti-leukaemic diterpenoid triepoxides

The crystal and molecular structures and absolute configuration of the title compounds, have been determined by three-dimensional, single-crystal, X-ray analysis. Crystals of triptolide (Ia) are monoclinic, space group P21, with a= 13·420(1), b= 6·256(1), c= 11·593(1)A, β= 118·09(1)°, and Z= 2. Crystals of tripdiolide (Ib) have the same space group, a= 13·680(2), b= 6·253(1), c= 11·684(1)A, β= 119·05(1)°, and Z= 2. The structure of (Ia) was determined by direct methods and refined to R 0·086, by least-squares methods, for 1044 independent reflections measured by counter diffractometry. The structure of (Ib) was found by direct application of the phase angles for (Ia), and refined by least-squares to R 0·082 for 1399 independent reflections.Each molecule has an 18(4 → 3)abeo-abietane skeleton, and tripdiolide is 2-hydroxytriptolide.