[reaction: see text] We present two new diffusion-edited NMR experiments, improved DECODES and HETDECODES, that sort the constituents in a mixture by their individual diffusion coefficients. These experiments should allow the partial NMR spectral assignment and cursory structure elucidation of compounds in a complex mixture as an aid in the dereplication of known or nuisance compounds.

The ' 3C n.rn.r. spectra of eighteen derivatives of ent-kaur-16-en-19-oic acid are recorded and the additivity of substituent effects is investigated. Application of these additive effects t o the prediction of the T -s h i f t s in new polysubstituted derivatives is assessed.Several studies of the ' 3C n.m.r. spectra of ent-kaurenoic (kaur-16-enoic) acids and kaurenolides have been reported and the identification of new substituted ent-kaurenoic acids has been achieved by a combination of 'H-and 13C-n.m.r. spectroscopy.'-' This paper concerns the 13C n.m.r. spectra of the hydroxylated ent-kaurenoic acids (I), (2), (4)+20).

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The spinosyns are a family of potent and highly selective insect control agents that display a favorable environmental profile. As some regions of the spinosyn molecule are recalcitrant to chemical modification, a targeted genetic approach was carried out to generate new analogues. The polyketide synthase (PKS) loading modules from the avermectin PKS of Streptomyces avermitilis and the erythromcyin PKS of Saccharopolyspora erythraea were each used to replace the spinosyn PKS loading module. Both of the resulting strains containing hybrid PKS pathways produced the anticipated spinosyn analogues. Supplementation of the culture media with a range of exogenous carboxylic acids led to the successful incorporation of these novel elements to yield further novel spinosyn molecules, some of which demonstrated potent and new insecticidal activities. Furthermore, it has been demonstrated that semisynthesis of such novel metabolites can then be used to generate active analogues, demonstrating the effectiveness of utilizing these complementary methods to search the chemical space around this template.