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978-3-8439-3533-3, Reihe Organische Chemie

Pardha Saradhi Peram
The Chemistry of Frog Pheromones

265 Seiten, Dissertation Technische Universität Braunschweig (2018), Softcover, A5

Zusammenfassung / Abstract

Frogs are known to use water soluble peptides for inter- and intraspecies chemical communication. However, it has been recently reported that frogs in the subfamily Mantellinae (Mantellidae: Mantellinae) from Madagascar disseminate volatile compounds for chemical communication. These volatile semiochemicals are isolated from the femoral glands present on ventral side of the shanks of these Mantellinae frogs. In this study, the femoral gland from several species of Mantellinae frogs were extracted in dichloromethane and were subsequently analyzed by GC/MS for the structural identification, as well as the chemical synthesis of bioactive volatile compounds. Unfortunately, the minute amounts of volatiles produced by the frogs did not permit structural analysis by multiple spectroscopic techniques.

The first part of this thesis describes the racemic and asymmetric synthesis of 8-methyl-9-decanolide, a volatile macrolide isolated from the frog Mantidactylus femoralis. The second part of this work describes the synthesis of a macrolide library consisting of several positional isomers of methyl-11-dodecanolide, which are produced by the frog Gephyromantis moseri. The preparation of the library was necessary to elucidate the methyl-branch positions of the naturally produced methyl-11-decanolides, which occur in miniscule (microgram) amounts and are difficult to isolate via normal chromatographic techniques. The synthetic library allowed for structural identification by mass spectral comparison of both the natural and synthetic methyl-11-dodecanolides. Studies towards stereoselective synthesis of gephyromantolide B are also presented, a macrolide produced by Gephyromantis redimitus.

The biosynthesis of macrolides in Mantellinae frogs is described in the third part of this work. A labelled macrolide, (S)-phoracantholide I-D5 was synthesized and fed to the Mantidactylus betsileanus frogs in feeding experiments to examine the occurrence of the labelled macrolide in femoral glands. The results of feeding experiments with labelled fatty acid precursors are presented as well.

The final part of this thesis presents the analysis of femoral gland extracts of mantellid, as well as gular gland extracts of frogs from the hyperoliid family found in various parts of central Africa. The results of the analysis of about 100 individuals from mantellid and 60 individuals from hyperoliid are tabulated.