Sigillin A, a Unique Polychlorinated Arthropod Deterrent from the Snow Flea Ceratophysella sigillata

Abstract

The snow flea Ceratophysella sigillata, a winter-active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. The structure of the major compound, sigillin A, was elucidated through isolation, spectroscopic analysis, and X-ray crystallography. Sigillin A showed high repellent activity in a bioassay with predatory ants. A promising approach for the total synthesis of members of this new class of natural compounds was also developed.

An Unprecedented Octahydro-3H-oxeto[2,3,4-ij]isochromene Ring System Formed by a Trichloromethyl-Anion-Induced Reaction Cascade

“…Although no antibacterial was observed until a concentration of 2 mM with human pathogenic bacteria, it might be possible that 1 indeed protects the springtails against microorganisms, because its concentration in the springtail can reach 4 mM. 1 In summary, although the original synthetic idea leading to sigillins was unsuccessful, a unique cascade reaction has been discovered, leading to a new, highly chlorinated tricyclic system.…”

“…1 They form a unique class of natural products with insect-repellent activity. C. sigillata, also called the snow flea because of its striking winter activity period, uses sigillin A as a chemical defense against various arthropod predators.…”

“…While we successfully synthesized 3, the otherwise straightforward synthesis was hampered by the last step, a ketone dichloromethylenation, which gave poor yields. 1 Sigillin F (2) is the second most abundant natural sigillin. Access to its didesoxy analogue 4 might be possible by opening of epoxide 5 with a trichloromethyl anion (Scheme 1), and the epoxide should in turn be accessible via epoxidation of the known alkene 6.…”

“…Access to its didesoxy analogue 4 might be possible by opening of epoxide 5 with a trichloromethyl anion (Scheme 1), and the epoxide should in turn be accessible via epoxidation of the known alkene 6. 1 We hoped that compound 3 could be developed by elimination of HCl from 4, thus avoiding dichloromethylenation. results were obtained with dimethyldioxirane (DMDO), 3 resulting in an almost quantitative conversion leading to a 1:2 mixture of the two epoxides 8 and the major compound 9, separable by column chromatography.…”

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“…4 The structure of sigillin A 4 was conrmed by X-ray analysis. 4 The structure of sigillin A 4 was conrmed by X-ray analysis.…”