Neural network-based QSAR and insecticide discovery: spinetoram.

Improvements in the efficacy and spectrum of the spinosyns, novel fermentation derived insecticide, has long been a goal within Dow AgroSciences. As large and complex fermentation products identifying specific modifications to the spinosyns likely to result in improved activity was a difficult process, since most modifications decreased the activity. A variety of approaches were investigated to identify new synthetic directions for the spinosyn chemistry including several explorations of the quantitative structure activity relationships (QSAR) of spinosyns, which initially were unsuccessful.

Discovery, synthesis, and insecticidal activity of cycloaspeptide E.

Several Penicillia and one Tricothecium strain produced a new, insecticidally active member of the cycloaspeptide family, with the proposed name cycloaspeptide E (1). The structure, which was determined on the basis of spectroscopic (NMR, UV, MS) data and Marfey amino acid analysis, was the tyrosine desoxy version of cycloaspeptide A (2). Two synthetic routes to compound 1 were developed: one a partial synthesis from 2 and the other a total synthesis from methyl alaninate hydrochloride.

Spinosyn g: proof of structure by semisynthesis.

[reaction: see text] Spinosyn G was isolated in the late 1980s as a minor component from the broth of our potent, fermentation-derived insecticide spinosad. Its structure was then tentatively identified as 5' '-epispinosyn A (3) on the basis of (1)H and (13)C NMR data, but the 4' '-epi compound 4 could not be conclusively ruled out with the data available. Described herein are unambiguous syntheses of both 3 and 4, whereby 3 was proved identical to the natural product.