Towards a viable grain beetle lure : practical syntheses of cucujolides and behavioural studies with Oryzaephilus surinamensis

Boden, Christopher David John (1992) Towards a viable grain beetle lure : practical syntheses of cucujolides and behavioural studies with Oryzaephilus surinamensis. University of Southampton, Doctoral Thesis.

Abstract

New syntheses of greatly improved efficiency and practicality are described for three macrolide components of the pheromone of the saw-toothed grain beetle Oryzaephilus surinamensis. The basic skeletons are constructed using Santelli's method for skipped (Z)-polyenes, which by application of a variant on the chlorite oxidation of aldehydes is extended to the efficient synthesis of (Z)-β-alkenoic acids. Details are given for the preparation and use of a useful Grignard reagent previously thought unobtainable. The enantiomers of all the chiral pheromones are prepared, along with a series of acyclic analogues and three structurally related macrolide components of the pheromones of various grain beetles of the genus Cryptolestes. A series of enyne analogues are constructed, and attempts made to facilitate cyclisation by complexation of the acetylene groups with dicobalt octacarbonyl. Behavioural studies are conducted to assess the response shown by O.surinamensis to the pheromones, singularly and in binary and tertiary mixtures, and to the various acyclic analogues. An apparent synergistic effect for 1-octen-3-ol is noted, and results obtained which suggest an advance in cost-effectivenessrelative to previous work. The adoption of a recently developed variant on the Mitsunobu lactonisation method gives dramatically improved yields for the lactonisation of the hydroxy acid precursors to all six macrolides, and gram quantities of the Oryzaephilus surinamensis pheromone components are produced.

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