The X-Ray Structure Analyses of the Natural Products Cedrelone and Chimonanthine

Grant, Ian James (1962) The X-Ray Structure Analyses of the Natural Products Cedrelone and Chimonanthine. PhD thesis, University of Glasgow.

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X-ray studies have been carried out on crystals of heavy atom derivatives of naturally -occurring organic compounds. Two structures have been successfully determined in this fashion: the triterpene cedrelone (C26H30O5) and the alkaloid chimonanthine (C22H26N4). Information on the structure of cedrelone was limited to spectral considerations alone, when a crystalline sample of the iodoacetate derivative was provided by Mr. S. G. McGeachin of Glasgow. The structure analysis was hindered initially by the iodine atom being close to a special position in the unit cell which gave rise to false symmetry in the initial Fourier syntheses. The fourth Fourier synthesis, however, resulted in most of the structure being determined and thereafter the complete structure was obtained and refined to give a discrepancy of, R =17.5%. The crystal and molecular dimensions were in agreement with accepted values although no attempt was made to locate atomic positions accurately Dr. G. F. Smith of Manchester University provided crystals of the dihydrobromide derivative of chimonanthine an alkaloid of the calycanthaceous variety. Chemical and spectral evidence had progressed to the stage where the structure was probably one of two possibilities. The first major problem in this structure analysis was the determination of the position of the bromide ions in the unit cell of the crystal. There were two bromide ions per asymmetric unit and the derivative crystallised in the tetragonal system; these two facts resulted in a very complex Patterson map which required much study before a solution was found. Thereafter the major problem was minimising the extremely large amounts of computer time required for this analysis. The structure and relative stereochemistry of chimonanthine have been determined and the structure was in fact one of the two structures proposed by the organic chemists. The crystal and molecular dimensions agree with accepted values within the limits of experimental accuracy and refinement of this structure has been carried out to give an average discrepancy between observed and calculated structure amplitudes of 14.9%. The final section of this thesis describes the work carried out under the supervision of Dr. E. Gelles lately of this Department. The copper ion catalysed hydrolysis of glycylglycine has been studied over a range of pH values and cupric ion concentrations. It has been established that the first complex formed between glycylglycine and cupric ione (Cu GG+) is the one responsible for catalysed hydrolysis and that subsequently formed complexes inhibit hydrolysis. These results are in agreement with other workers theoretical predictions The structure analysis of cedrelone was carried in conjunction with Dr. J. A. Hamilton of this department and the kinetic studios were a continuation of experiments first started by Mr. J. M. Wilson lately of this department.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1962
Depositing User: Enlighten Team
Unique ID: glathesis:1962-79460
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 09:30
Last Modified: 05 Mar 2020 09:30

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