Piperitone-derived saturated lactones: synthesis and aphid behavior-modifying activity.

Area of Science:

• Organic Chemistry
• Insect Chemical Ecology
• Agrochemistry

Background:

• Piperitone, a naturally occurring monoterpene, exhibits weak deterrent effects on aphids.
• Structural modification of natural products is a key strategy for discovering novel bioactive compounds.
• Understanding structure-activity relationships is crucial for developing effective pest management solutions.

Purpose of the Study:

• To synthesize novel saturated lactones based on the p-menthane system.
• To evaluate the antifeedant activity of these lactones against Myzus persicae.
• To investigate the impact of structural modifications (lactonization, chirality) on aphid deterrent activity.

Main Methods:

• Synthesis of racemic and enantiomerically pure lactones from piperitone derivatives.
• Structural confirmation using spectroscopic data.
• Behavioral assays to assess aphid responses to piperitone and synthesized lactones.

Main Results:

• Piperitone itself showed minimal deterrent activity towards Myzus persicae.
• Lactonization of piperitone dramatically altered its biological activity, inducing negative aphid responses.
• Specific lactones, (1R,3S,6R)-3-isopropyl-6-methyl-9-oxabicyclo[4.3.0]nonan-8-one and trans-3-isopropyl-6-methyl-9-oxabicyclo[4.3.0]nonan-8-one, exhibited potent and durable deterrent effects.
• These active lactones inhibited aphid probing and reduced phloem sap quality.

Conclusions:

• The introduction of a lactone moiety and specific stereochemical configurations significantly enhances the aphid deterrent activity of piperitone derivatives.
• The most potent lactones effectively prevent aphids from feeding by interfering with probing behavior and phloem sap uptake.
• These findings highlight the potential of tailored lactone structures as novel aphid control agents.