Sigillins from Springtails Are Potent Natural Insecticides

Abstract

Sigillins are highly chlorinated natural products from the springtail Ceratophysella sigillata (Collembola) that are used to deter arthropod predators. We report here the isolation and structure elucidation of sigillin F, a hydrogenated benzopyranone compound bearing two trichloromethyl groups, and the synthesis of trideoxysigillin ( 8), a non-natural compound representing the basic scaffold of the sigillins. Sigillins A and F showed insecticidal activity toward various insects, similar to the commercial insecticide imidacloprid, whereas 8 was inactive. The highest mortality was observed for the aphids Megoura viciae and Myzus persicae, but other insect species were also susceptible. Sigillins act as noncompetitive antagonists of the GABA receptor. This mode of action is identical to that of known insecticides with high chlorine content such as dieldrin or endosulfan. The high content of sigillins in C. sigillata, more than 4 mM in concentration, indicates self-resistance. Strikingly, the Collembola and humans have both arrived at the same target with related types of compounds to combat insects.

Cyclopropane Hydrocarbons from the SpringtailVertagopus sarekensis─A New Class of Cuticular Lipids from Arthropods

“…The Collembola form a sister class to the Insecta, which diverged from the Insecta 400 mya. Their chemistry is poorly characterized compared to insects, but their unique chemical defense using compounds such as pyridopyrazines , or sigillins , has occasionally been investigated. As is probably the case in all arthropods, the collembolan cuticle is covered by a thin lipid film that is thought to prevent desiccation and may have additional functions such as signaling and protection against microbial attack, as has been shown in insects.…”

Dynamic Kinetic Resolution of γ-Substituted Cyclic β-Ketoesters via Asymmetric Hydrogenation: Constructing Chiral Cyclic β-Hydroxyesters with Three Contiguous Stereocenters

“…Upon initial investigation, we noticed that chiral cyclic β-hydroxy esters with contiguous stereocenters are important structural motifs widely found in bioactive natural products and pharmaceuticals (Figure ). Therefore, we first intended to study the asymmetric hydrogenation of γ-substituted cyclic β-ketoesters with chiral spiro ruthenium complex RuCl 2 -( S )-Xyl-SDP/( R , R )-DPEN (( S a , R , R )- 3 ), an efficient catalyst for the asymmetric hydrogenation of racemic α-substituted aldehydes and ketones via DKR in the presence of strong base such as t BuOK . We selected ethyl 3-phenyl-2-oxocyclohexane-1-carboxylate ( 1a ) as a model substrate and performed the hydrogenation under the general conditions in the presence of 0.2 mol % of ( S a , R , R )- 3 , and no hydrogenation product was observed (Scheme ).…”

Total Synthesis of (−)-Sigillin A: A Polychlorinated and Polyoxygenated Natural Product

“…Schulz’s group reported the synthesis of desoxysigillin A, which lacks hydroxy groups at positions C-5 and C-6 (Scheme ). , They found that the installation of a gem -dichloroalkene moiety, one of the unique functional groups of 1 , was quite challenging and gave the desired compound 11 in only 2% yield. Thus, the major challenge in the synthesis of this natural product is the introduction of these hydroxy groups and the gem -dichloroalkene group.…”

“…Boron would attack enone 24 to avoid the steric hindrance of the bulky diisopropylsilyl group. As mentioned in previous reports, , transformation of the carbonyl group into dichloroalkene proved to be problematic for us. Several methods for the formation of dichloroalkene from ketone are reported .…”