The electron microscopy of alkali halides

• Main Author: Hobbs, L. W.
• Published: University of Oxford 1972
• Subjects: 546
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.459371

The various groups into which the triterpenes are divided are defined and emphasis is placed on the structural relationships which exist between these groups. A brief description is given of the methods used in the determination of the structure of triterpenes with particular reference to β-asyrin (I), a member of the oleanane (II) group. Recent progress in the problems of biogenesis and the total synthesis of triterpenes is reviewed. All approaches, so far investigated, to the synthesis of pentacyclic triterpenes involve the fusion of two bicyclic moities representing rings A and B and rings D and E of the proposed structure. This thesis describes attempts to synthesise pentacyclic triterpenes of the oleanane (II) group, via the tetracyclic-cis-ketone (IIIa), the tetracyclic-trans-ketone (IIIc) or the tetracyclic-αβ-unsaturated-ketone (IVa).