Tracking the cryptic pumiliotoxins

Simple Indolizidine and Quinolizidine Alkaloids

This review of simple indolizidine and quinolizidine alkaloids (i.e., those in which the parent bicyclic systems are in general not embedded in polycyclic arrays) is an update of the previous coverage in Volume 55 of this series (2001). The present survey covers the literature from mid-1999 to the end of 2013; and in addition to aspects of the isolation, characterization, and biological activity of the alkaloids, much emphasis is placed on their total synthesis. A brief introduction to the topic is followed by an overview of relevant alkaloids from fungal and microbial sources, among them slaframine, cyclizidine, Steptomyces metabolites, and the pantocins. The important iminosugar alkaloids lentiginosine, steviamine, swainsonine, castanospermine, and related hydroxyindolizidines are dealt with in the subsequent section. The fourth and fifth sections cover metabolites from terrestrial plants. Pertinent plant alkaloids bearing alkyl, functionalized alkyl or alkenyl substituents include dendroprimine, anibamine, simple alkaloids belonging to the genera Prosopis, Elaeocarpus, Lycopodium, and Poranthera, and bicyclic alkaloids of the lupin family. Plant alkaloids bearing aryl or heteroaryl substituents include ipalbidine and analogs, secophenanthroindolizidine and secophenanthroquinolizidine alkaloids (among them septicine, julandine, and analogs), ficuseptine, lasubines, and other simple quinolizidines of the Lythraceae, the simple furyl-substituted Nuphar alkaloids, and a mixed quinolizidine-quinazoline alkaloid. The penultimate section of the review deals with the sizable group of simple indolizidine and quinolizidine alkaloids isolated from, or detected in, ants, mites, and terrestrial amphibians, and includes an overview of the "dietary hypothesis" for the origin of the amphibian metabolites. The final section surveys relevant alkaloids from marine sources, and includes clathryimines and analogs, stellettamides, the clavepictines and pictamine, and bis(quinolizidine) alkaloids.

Towards stereochemical control: A short formal enantioselective total synthesis of pumiliotoxins 251D and 237A

A concise enantioselective synthesis of the advanced intermediate 5 for the synthesis of pumiliotoxins (Gallagher's intermediate) is described. The synthesis started from the regio- and trans-diastereoselective (dr = 98:2) reductive 3-butenylation of (R)-3-(tert-butyldimethylsilyloxy)glutarimide 14. After O-desilylation and Dess-Martin oxidation, the resulting keto-lactam 10 was subjected to a highly trans-stereoselective addition of the methylmagnesium iodide to give carbinol 11 as sole diastereomer. An efficient ring closure procedure consisting of ozonolysis and reductive dehydroxylation provided the indolizidine derivative 5, which completed the formal enantioselective total synthesis of pumiliotoxins 251D and 237A.

Theories of Biodiversity Value

The discussion of the calculus of biodiversity values in Chap. 5 is the final requisite prop for the stage across which this chapter parades accounts of how biodiversity is supposed to be valuable. The selection of these accounts is generous and represents a great majority of discussions on this topic, though it is not all-inclusive. It does include, among other theories, the theory that biodiversity is valuable for “unspecified moral reasons” (Sect. 6.1), that it is valuable as a resource (Sect. 6.2), as a service provider (Sect. 6.3), as a sustainer of human life (Sect. 6.4), as a key to human health, both as pharmacopoeia and as an inoculation against infection (Sect. 6.5), as the progenitor of human biophilic tendencies (Sect. 6.6), as a generator of (more) value (Sect. 6.7), as font of knowledge (Sect. 6.8), as having option (and quasi-option) value (Sect. 6.9), as transformative (Sect. 6.10), as having experiential value (Sect. 6.11), and as an expression of the natural order (Sect. 6.12). The chapter concludes (Sect. 6.13) with some proposals that are not customarily offered as self-contained theories of biodiversity value, but that are often suggested as still heavily influencing evaluation. These include what conservation biologists call “viability” and “endangerment” as well as conservation “efficiency”. Section 6.13 concludes with an extended discussion of the significance for biodiversity’s value of the history of human impingements on the natural world.

Recent developments in the field of arrow and dart poisons

Arrow and dart poisons, considered as conventional natural sources for future drug discovery, have already provided numerous biologically active molecules used as drugs in therapeutic applications or in pharmacological research. Plants containing alkaloids or cardiotonic glycosides have generally been the main ingredients responsible for the efficacy of these poisons, although some animals, such as frogs, have also been employed. This paper, without being exhaustive, reports the greater strides made during the past 15 years in the understanding of the chemical nature and biological properties of arrow and dart poison constituents. Examples both of promising biological properties shown by these molecules and of crucial discoveries achieved by their use as pharmacological tools are given. Further studies of these toxic principles are likely to enable scientists to find new valuable lead compounds, useful in many fields of research, like oncology, inflammation and infectious diseases.