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The search for a toxicant in native Gastrolobium seed historically reported to make Australian native fauna toxic to the introduced cat and dog

Proceedings of the Vertebrate Pest Conference, Volume 20 (2002)

The decline and extinction of Australian mammals since the arrival of Europeans has been catastrophic. Attempts to reintroduce threatened species of native mammals to their former ranges have failed due to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis silvestris catus). Baiting with poisoned meat baits will control foxes, but feral cats are generally unwilling to consume a bait. This has seen recent reintroduction attempts fail due to cat predation, possibly involving only a few individual animals. Historical anecdotes from Western Australia record the death of cats and dogs after feeding on a number of the native animal species, with the bronzewing pigeons, Phaps chalcoptera and P. elegans, most frequently mentioned. The toxicity of the pigeons has been attributed to the birds’ feeding on seeds from plants of the Gastrolobium genus. Such a mechanism has been suggested to have aided the survival of 35- to 5,500-g mammals in southwest Western Australia when such species have disappeared elsewhere. Analysis of the seeds of members of the genus Gastrolobium has found extremely high levels of organically bound fluorine. Previous studies report this fluorine to be stored in the seeds as monofluoroacetate (MFA – synonymous with Compound 1080). However, a number of the poisoning anecdotes suggest toxicity of the pigeon skeleton, and report times to death which appear too rapid for the known action of MFA or “1080.” The objective of this research is to examine the authenticity of the historical anecdotes and the feasibility of using a skeletally retained natural plant toxicant to aid the reintroduction of native fauna. Those individual cats and foxes effecting the predation may be removed at the first predatory event if the reintroduced fauna were toxic to the predating animal. This is anticipated to greatly improve the success rate of future reintroduction programs. Exhaustive extraction of Gastrolobium seeds with a variety of solvents and subsequent analysis utilizing a fluoride ion-specific electrode, 19F nuclear magnetic resonance, and other techniques has established the presence of a number of fluorinated and alkaloid compounds. Determination of the identity and toxicity of these compounds is expected to identify a compound(s) which may explain many of the historical poisoning anecdotes and could also provide a method for the control of feral cats in native mammal reintroduction programs.

Cover page: The search for a toxicant in native Gastrolobium seed historically reported to make Australian native fauna toxic to the introduced cat and dog

Thesis
Peer Reviewed

Palladium-Mediated Formation of Alkyl–Nitrogen Bonds

Peacock, David Matthew
Advisor(s): Hartwig, John F

UC Berkeley Electronic Theses and Dissertations (2017)

The following dissertation discusses reactions of palladium complexes to form sp3 carbon–nitrogen bonds. Both stoichiometric reductive elimination reactions to form alkylamines from characterized alkylpalladium(II) complexes and new palladium-catalyzed methods for the synthesis of N-alkylbenzophenone imines are reported.

Chapter 1 provides an overview of methods for the N-alkylation of nitrogen nucleophiles. Metal-catalyzed substitution reactions of nitrogen nucleophiles with alkyl electrophiles are discussed with a focus on the fundamental organometallic reactions that may form carbon–nitrogen bonds in these reactions. Examples of reductive elimination reactions from characterized alkylmetal complexes are covered in more detail because of their relevance to later chapters.

Chapter 2 discusses continued work in the Hartwig group studying the reductive elimination of norbornylamines from syn-2-methylnorbornylpalladium(II) amido complexes. This work focuses on the effects of phosphine ancillary ligands on the rate of reductive elimination and yield of alkylamine. These studies led to the design of bidentate P,O ligands that stabilize Pd(II) amido complexes while still enabling the reductive elimination of alkylamines to occur in good yield.

Chapter 3 presents the reductive elimination of N-neopentyl anilines and N-neopentyl imines from palladium(II) complexes. The P,O ligand structures developed as part of the work described in Chapter 2 proved particularly valuable to the study of neopentylpalladium(II) complexes and enabled the synthesis of stable, four-coordinate Pd(II) anilido and methyleneamido complexes that undergo reductive elimination to form N-neopentyl anilines and N-neopentyl imines in good yields.

Chapter 4 discusses the development of palladium catalysts for the cross-coupling of imines and primary alkyl bromides. The addition of fluorinated iminoquinolines as ancillary ligands was found to greatly increase the rate of the reaction. Mechanistic studies suggest that this reaction occurs through a two-electron pathway that may involve oxidative addition to a cyclometallated palladium(II) complex.

Chapter 5 expands the palladium-catalyzed cross-coupling of imines to include reactions with synthetically valuable secondary and tertiary alkyl halides. This method was applied to form a variety of imines bearing secondary and tertiary alkyl groups on nitrogen. Mechanistic studies suggest that this reaction occurs through single-electron transfer from a palladium(0) complex to form an alkyl radical intermediate. The intermediacy of this alkyl radical enabled this method to be expanded to include the intramolecular carboamination of unsaturated alkyl bromides.

Cover page: Palladium-Mediated Formation of Alkyl–Nitrogen Bonds

Article

1080, toxic sugars, alkaloids, and a dead cat: The search for a toxicant in Australian Gastrolobium seed

Proceedings of the Vertebrate Pest Conference, Volume 21 (2004)

It was hypothesised that reintroduction of Australian native mammals, currently being severely impacted by feral cat predation, would be more successful if these mammals could have a retained toxicity as discussed in historical accounts. Seeds from the Australian genus Gastrolobium (Fabaceae: Mirbelieae) were analysed in the search for a toxicant that would explain historical accounts of toxic wildlife. Numerous accounts referring to bronzewing pigeons having toxic bones were specifically noted. Analysis of this seed found no evidence for rapidly toxic alkaloids previously reported as being extracted from the leaves of York Road poison and box poison. However, evidence for the presence of organo-fluorine compounds in addition to the reported fluoroacetate (Compound 1080) was discovered. A limited cat dosing trial found that a highly fluorinated box poison seed caused a cat to cease respiration in 82 minutes, but its chloroform extract produced no adverse physiological response. In addition, citrate accumulation appeared more rapid and acute with increasing seed ‘total fluorine.’