Abstract

For decades considerable research has focused on improving the efficiency of crop protection. Many naturally occurring biodegradable compounds have often been used as pesticides and with increased environmental concerns, the identification of biologically active natural products has attracted significant attention. Fish toxicity has often been used as a measure of pesticidal activity. Several Southeast Asian mangrove species have been shown to possess ichthyotoxic properties. A bioassay of the extracts obtained from Heritiera littoralis, a Philippine mangrove plant, indicated toxicity toward fish thus suggesting the possibility of their use as pesticides. Three sesquiterpene lactones, Heritianin, Vallapin, and Vallapianin have been isolated from H littoralis. Vallapin showed activity against the cotton boll weevils. The aim of this project is to attempt the total synthesis of these lactones. The key reaction in the total synthesis is the construction of the lactone moiety. Based on literature precedent it appeared that an intramolecular Reformatsky reaction is the method of choice to construct the lactone. Model studies were carried out successfully with 6methoxy- l-tetralone. The total synthesis of the target molecules is now underway and seven steps in the proposed ten step synthesis have been completed in 27% overall yield. The asymmetric synthesis of the target molecules will also be carried out.

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Chemistry

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