The mass spectra of griseofulvin analogues. Characteristic fragmentation processes in the mass spectra of spiro-cyclohexenones and spiro-cyclohexanones containing the griseofulvin skeleton

The mass spectra of a number of griseofulvin analogues have been examined and the fragmentations, which are characteristic of the basic skeleton of the molecule, have been determined. In all of the different structural types examined, the ring cleavages which predominate are found tol occur by fission of one or more of the bonds attached to the spiro carbon atom. The degree of unsaturation in the spiro-cyclohexane ring system is found to controll the type of fragmentation which occurs and the type of ring system which is present can therefore be identified by its mass spectrum.     

Management Planning and Control in Multi-Branch Banking

This paper describes a model developed for a British bank to assist management in establishing branch goals, evaluating performance and planning new locations. Econometric methods are used to produce a set of equations which effectively predicts the main dimensions of branch performance.     

The structure of some methyl and benzyl malonate derivatives of pyrimidine

Reaction of 2,4,6-trichloropyrimidine with sodium dibenzylmalonate in p-dioxane gave 4,6-dichloro-2-(dibenzylmalonyl)pyrimidine, while reaction of 2,4,6-trichloropyrimidine with sodium dimethylmalonate yielded both 4,6-dichloro-2-(dimethylmalonyl)pyrimidine and 2,2-bis-(4,6-dichloropyrimidin-2-yl)dimethylmalonate. Structural studies using nmr, ir and uv spectroscopy indicate that for the former two compounds in basic solvent, an equilibrium exists between the keto forms and resonance-stabilized enolate ions.     

Agropine,a new amino acid derivative from crown gall tumours

Agropine, an unusual compound produced in plant tumours was shown by mass spectrometry and proton and carbon-13 nmr spectroscopy to be a bicyclic derivative of glutamic acid and a hexitol sugar.     

On the use of Bennett's acceptance ratio method in multi-canonical-type simulations

A common strategy for mapping coexistence curves is to employ multi-canonical (MUCA) sampling to simulate along a macrostate path connecting two phases. Central to this approach is the task of accurately calculating the importance weights used in the MUCA procedure, which are needed for both effective sampling and accurate determination of phase boundaries. The purpose of this study is to develop a strategy for determining the importance weights that is built upon Bennett's optimized acceptance ratio method. This approach is shown to be closely related to transition matrix schemes, and is used to compute the vapor-liquid equilibrium of a Lennard-Jones fluid and the liquid-liquid equilibrium of a n-hexane/n-perfluorohexane mixture. For the Lennard-Jones system, the importance weights as a function of the number of particles "N" (at fixed temperature and volume) are obtained by using Bennett's method to estimate free energy differences between N and N+1 particle systems over the desired range of N values. In this application, the method is found to perform slightly better than a related transition matrix scheme. For the n-hexane/n-perfluorohexane liquid mixture, the method is designed to obtain weights as a function of composition (for fixed temperature, pressure, and total number of particles); in this case, the method is found to outperform the Gibbs ensemble approach.     

The fast atom bombardment mass spectra of glucosinolates and glucosinolate mixtures

The behaviour of glucosinolates and desulphoglucosinolates under fast atom bombardment conditions has been investigated. Relatively little fragmentation was noted in the mass spectra of these compounds. The positive ion fast atom bombardment mass spectra of glucosinolates exhibited abundant cationized and protonated molecula ions, thus complementing the previously reported electron impact and chemical ionization mass spectra of these compounds. Desulphoglucosinolates yield only the protonated molecular ion. Under negative ion conditions the spectra of glucosinolates were dominated by the molecular anion and this has been used as a means of analysing a crude plant extract containing a complex mixture of glucosinolates.