X-Ray Crystal Structure Analyses of a Sultone and Some Diterpenoids

Birnbaum, Karin Bjamer (1968) X-Ray Crystal Structure Analyses of a Sultone and Some Diterpenoids. PhD thesis, University of Glasgow.

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Abstract

This thesis is divided into two parts, one theoretical (Part I) and the other experimental (Part II). The first part deals with the theory of X-ray diffraction and with various methods for determination and refinement of structures. Some of these methods have been applied in the study of four organic compounds. This is described in the experimental section. The study of sultone B, C15H14O3S, was undertaken in order to determine the partially unknown configuration and to obtain accurate molecular dimensions. The structure was found to be where the heterocyclic ring is in a distorted half-chair conformation with the phenyl group axial and cis to the methyl group, which is quasi-equatorial. Some bond lengths are: S-O (peripheral) 1.431+/-0.003, S-O(C) 1.595+/-0.004, S-C 1.797+/-0.005 and Csp2-O 1.426+/-0.005 A. Three derivatives, one of a diterpene and two of diterpenoids, were studied in order to establish their structures and/or stereochemistry. The determinations were all sufficiently accurate to allow fairly detailed discussions of bond lengths and angles. Steric strain, which causes conformational distortions, has been observed in all three structures. The bond angles are influenced appreciably by this effect while only a few bond lengths are affected by it. Taxadienetetraol, C20H32O4, a new diterpene, was isolated from yew heartwood (Taxus baccata L.) by Dr. Halsall's group. The crystal structure and absolute configuration of the p-bromobenzoate of a dihydro-anhydro-acetonide derivative of taxadienetetraol, C30H39O4Br, was found to be During the formation of this derivative an unexpected rearrangement of the taxane skeleton took place. The derivative contains a five-, a six- and a seven-membered carbon ring in contrast to the two six- and one eight-membered rings of the parent tetraol. The cyclohexane ring adopts the chair form. It is trans-fused to the cycloheptane ring which occurs in a twisted boat conformation. The envelope-shaped cyclopentene ring and the acetonide ring in the half-chair form are, respectively, cis- and transfused to the cycloheptane ring. Labdanolic and eperuic acids have the same configuration at C(13), being otherwise antipodal. The common configuration at C(13) was undefined. The crystal structure of the p-bromophenacyl ester of labdanolic acid, C28H41O4Br, was found to be The configuration at C(13) was thus established to be (S) (Prelog's notation). The two six-membered rings in the decalin system occur in the chair form and are trans-fused to each other. The analysis of the crystal structure and absolute configuration of a p-bromobenzoate derivative of the diterpenoid E-caesalpin, C27H33O6Br, gave the following result The three six-membered rings are fused to form a trans-anti-trans system. Rings A and B occur in the chair form while the unsaturated ring C adopts a distorted halfchair conformation. An intramolecular hydrogen bond (2.649 A) between the two 1,3-diaxial hydroxyl groups was found.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry, Physical chemistry
Date of Award: 1968
Depositing User: Enlighten Team
Unique ID: glathesis:1968-78471
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:16
Last Modified: 30 Jan 2020 15:16
URI: http://theses.gla.ac.uk/id/eprint/78471

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