Untersuchungen mit optischer Rotationsdispersion, CXV. α-Hydroxysäure-Molybdat-Komplexe

On the use of Guinier-Hägg film data for structure analysis

From the information contained in one powder photograph obtained in a Guinier-Hägg camera the crystal structure of (NH4)4[(MoO2)4O3] (C4H3O5)2 · H2O, only known in microcrystalline form, has been determined and refined to a moderate degree of accuracy. The work has comprised step-scanning measurement of the intensity profile, indexing with a trial-and-error program, determination of the Mo positions from an incomplete Patterson function derived from resolved integrated intensities, and finally localization of light non-hydrogen atoms and structure refinement by a series of Fourier calculations and profile analyses.

The material crystallizes in the monoclinic system, space group C 2, with two formula units in a cell of dimensions a = 14.572(2) Å, b = 10.114(2) Å, c = 11.461(2) Å and β = 121.45(1)°. Since as many as 51 parameters are involved the atomic coordinates obtained are approximate, but the main features of the structure are established. The structure contains discrete [(MoO2)4O3 (C4H3O5)2]4− ions having a twofold axis through an oxygen atom.

Ester-type cephalotaxus alkaloids from Cephalotaxus harringtonia var. drupacea

Three alkaloids, neoharringtonine, homoneoharringtonine and 3'S-hydroxyneoharringtonine, were isolated from the leaves and stems of Cephalotaxus harringtonia var. drupacea. Their structures were established by spectroscopic methods, including two-dimensional NMR and CD spectra, and their antileukaemic activity was evaluated using P-388 leukaemia cells.