L. Riva di Sanseverino

Three dimensional structure of adenosine triphosphate.

The three dimensional structure of adenosine triphosphate in the hydrated disodium salt is reported to a resolution of 0.9 Å.

The behaviour of apatite-based ceramics in relation to the critical 1150°–1250°C temperature range

Characterization of synthetic calcium phosphates is reported and compared with previous studies. Barium hydroxyapatite was also synthesized. Shrinkage on sintering, water absorption, tensile strength, porosity and X-ray diffraction patterns were studied. Hydroxyapatite and beta-tricalcium phosphate show compositional and mechanical property variation dependent on sintering temperatures. The property change on introduction of barium removes the practical value. X-ray diffraction analysis is considered essential before clinical use due to sensitivity of composition to sintering conditions.

The molecular and crystal structure of 2α-bromoarborinone : The structure of the triterpene arborinol

Abstract The molecular structure and stereochemistry of the triterpene arborinol was obtained from a three-dimensional X-ray diffraction study of 2α-bromoarborinone. The molecule is shown to be pentacyclic with a 13β, 14αtrans configuration of the methyl groups at the C/D ring junction, not previously found among pentacyclic triterpenes. The space group is P212121, with four molecules in the unit cell: a = 12·84 b = 8·68 c = 22·46 A. The value of R = (Σ|Fo| − |Fc|)/Σ|Fo| is 12·4% for 1719 observed reflections. The implications of the structure for the ferenen-group of triterpenes are discussed.

Characterization of synthetic apatites for bioceramic implants

Hydroxyapatite has been studied as a substance suitable for surgical substitution of bones and teeth with emphasis on its biocompatibility. The present work tries to identify the characteristics of this material either from the chemico-physical-structural point of view, or from the technological one, evaluating the best performance. By X-ray, i.r., thermal, chemical and SEM analyses, the relationship of different phenomena involved in the sintering was evaluated. Technological tests demonstrated the stability and the workability characteristics. In particular, the influence of CO2 was studied, in connection with the most suitable technique for hydroxyapatite (HAP) sintering, considering the eventual aims and requirements for industrial production.

The use of phosphorus and boron sulfides as sulfurizing agents: a general route to dithiocarboxylate complexes

Abstract The sulfides P 4 S 10 and B 2 S 3 react with the acyl complexes (C 5 H 5 )Fe(CO) 2 COR and (CO) 5 MCOR (M  Mn, Re; R  CH 3 , C 6 H 5 ) to yield dithiocarboxylate complexes (C 5 H 5 )Fe(CO)SSCR and (CO) 4 M SSCR in which the ligand is bidentate. With the iron complexes reactions lead also to (C 5 H 5 )Fe(CO) 2 SC(S)R, and an X-ray structural study of the latter (X  CH 3 ) has confirmed that the dithioacetate ligand is S-monodentate.

The crystal and molecular structure of a mineral diterpene, bombiccite, C20H34

A natural product found in lignite mines has been assigned the structure ofa-dihydrophyllocladene by crystal structure analysis. The crystals are triclinic, P1, a = 11.39 (7), b = 21.29 (5), c = 7.45 (1)/~,, tt = 94.6 (1), fl = 101.8 (2), y = 81.5 (1) ° and Z = 4. The structure has been solved by direct methods followed iteratively by Fourier syntheses and least-squares refinement of site occupation factors of the resulting peaks. The four independent molecules have the same configuration at the six chiral centres. Rings A, B and C assume the chair conformation with trans junctions, and ring D is an envelope. 1311

The structure of the steroidal bromosapogenins

In contrast to the 25R-sapogenins, which yield two isomeric monobromo-derivatives, the 25S-sapogenins yield only single monobromo-derivatives. Infrared absorption, proton magnetic resonance, and X-ray crystallographic measurements on certain of these compounds are reported, and the conclusions to be drawn as to steric configuration are discussed. It is agreed that 23a- and 23b-bromo-25R-sapogenins have bromine in equatorial and axial positions, respectively. In 23-bromo-25S-sapogenins the bromine is equatorial. 23,23-Dibromo- and 23-iododerivatives of certain sapogenins and a series of deutero-derivatives have been prepared.

A crystallographic and theoretical study of the conformation of DOET and its significance for the hallucinogenic amphetamines

The crystal and molecular structure of 2,5‐dimethoxy‐4‐ethyl‐α‐methyl‐phenylethylamine (DOET) has been determined by X‐ray crystallography and the conformation of the side chain has been examined theoretically by the use of a potential energy calculation. There is no indication in the solid state of any intra or inter‐molecular hydrogen bonding. The isopropylamine side chain is staggered to the plane of the benzene ring. The α‐methyl group is fully extended (antiplanar) whereas the amino group is orientated back towards the ring (synclinal). The potential energy calculations show the existence of 6 minima, one of which corresponds to the crystal position. The calculations also show that the energy differences between the various minima of the side chain are very small. The relationship of these data to the conformations of the hallucinogens, mescaline and 2,4,5,‐trimethoxyamphetamine is discussed.

The crystal and molecular structure of the epoxybromo derivative of atractyligenin.

Abstract The complete configuration of atractyligenin has been obtained by a three-dimensional single-crystal X-ray difiraction study. Previous structural work has been confirmed, in particular the configuration of the epoxy group. The space group is C2, with four molecules in the cell, a = 19·005, b = 7·165, c = 14·450 A, β = 108° 31′, and the final R is 0·125 for 1320 observed reflections. The stress in the molecule (as indicated by the torsional angles) and the molecular packing are discussed.

X-Ray analysis of the structure of (±)-1-acetyl-3-methylaspidospermidine 9-methiodide

The structure of (±)-1-acetyl-3-methylaspidospermidine 9-methiodide was determined. The crystals are triclinic, space group P, cell constants a= 16·21, b= 14·53, c= 11·08 A, α= 102·10, β= 108·05, γ= 102·75°, Z= 4. The structure was solved by the heavy-atom method and refined isotropically to R= 12·8%. The conformation of the two enantiomorphic molecules in the asymmetric unit is discussed in detail and compared with that of related compounds for which torsion angles were calculated by use of co-ordinates reported in the literature.