- Structural and mechanistic studies of the copper(II)-assisted ortho-hydroxylation of benzoates by trimethylamine N-oxide
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N-benzoyl-2-methylalanine (H2L1) is ortho-hydroxylated stereoselectively by trimethylamine N-oxide (TMAO) in the presence of copper(II). The experimental structure of [Cu(L1)(TMAO)2] suggests that the oxygen transfer agent TMAO transfers the oxygen atom to copper(II), and (L1)2-, coordinated to copper(II) by a carboxylate oxygen and the amide nitrogen donor, is well pre-organized for an oxygen transfer from copper to the ortho carbon atom of the benzene ring. Product analyses as a function of reaction time of the copper(II)-mediated ortho-hydroxylation reaction with H2L1 and various derivatives support the suggestion of a reactive copper-oxo or copper-hydroxo intermediate, stabilized by a five-membered chelate with hard carboxylate and N-amide donors. The analysis also suggests that there is a pre-equilibrium with a Cu:L=1:1 ratio, and this might involve Cu/L2-/TMAO or dicopper complexes. Depending on the ligand H2L, complexation with the salicylate product may inhibit the ortho-hydroxylation reaction.
- Buijs, Wim,Comba, Peter,Corneli, Danny,Pritzkow, Hans
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- Synthesis of cyclic depsipeptides and peptides via direct amide cyclization
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The 2,2-disubstituted 2H-azirin-3-amines 7 (2,2-disubstituted 3-amino-2H-azirines) were used as amino-acid synthons in the preparation of medium-sized cyclic depsipeptides and peptides derived from salicylic acids 6 and anthranilic acid 19, respectively.
- Villalgordo, Jose M.,Heimgartner, Heinz
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p. 748 - 766
(2007/10/03)
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- Copper(II) mediated Aromatic Hydroxylation by Trimethylamine N-Oxide
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Quantitative orthohydroxylation of N-benzoyl-2-methylalanine (1) occurs through its copper(II) salt oxidation by trimethylamine N-oxide; transitory formation of a Cu(III) species is proposed.
- Reinaud, Olivia,Capdevielle, Patrice,Maumy, Michel
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p. 566 - 568
(2007/10/02)
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