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A chiral ligand for the rhodium‐catalyzed asymmetric 1,4‐addition of an arylboronic acid to a coumarin substrate that could markedly reduce catalyst loading was developed using interplay between theoretical and experimental approaches. Evaluation of the transition states for insertion and for hydrolysis of intermediate complexes (which were emphasized in response to the experimental results) using DFT calculations at the B97D/6‐31G(d) level with the LANL2DZ basis set for rhodium revealed that: (i) the electron‐poor nature of the ligands and (ii) CH–π interactions between the ligand and coumarin substrates played significant roles in both acceleration of insertion and inhibition of ArB(OH)2 decomposition (protodeboronation). The computationally‐designed ligand, incorporating the above information, enabled a decrease in the catalyst loading to 0.025 mol% (S/C=4,000), which is less than one one‐hundredth relative to past catalyst loadings of typically 3 mol%, with almost complete enantioselectivity. Furthermore, the gram‐scale synthesis of the urological drug, (R)‐tolterodine (l)‐tartrate, was demonstrated without the need of intermediate purification.magnified image

A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) for the analysis of emamectin residues in agricultural products was developed using a prepared mouse monoclonal antibody. The working range was 0.3-3.0 ng/mL, and the 50% inhibition concentration (IC(50)) was 1.0 ng/mL. The assay was sufficiently sensitive for analysis of the maximum residue limits in agricultural products in Japan (>0.1 microg/g). Emamectin residues contain the following metabolites: the 4''-epi-amino analogue, the 4''-epi-(N-formyl)amino analogue, the 4''-epi-(N-formyl-N-methyl)amino analogue, and the 8,9-Z isomer. The dc-ELISA reacted with these compounds at ratios of 113, 55, 38, and 9.1% of the IC(50) value of emamectin benzoate. Seven kinds of vegetables were spiked with emamectin benzoate at concentrations of 15-300 ng/g, and the recoveries were 91-117% in the dc-ELISA. The dc-ELISA results agreed reasonably well with results obtained by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using spiked samples and actual (incurred) samples. The results indicate that the dc-ELISA was useful for the analysis of emamectin benzoate residues in agricultural products.

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