Influence of aromatic nitro-substituents on auto-reusability of oxime-based fluoride receptors

Abstract

The interaction of fluoride ion with three oxime based receptors containing additional aromatic nitro-substituents was studied by using colorimetric and NMR spectroscopy. Colorimetric responses of the receptors towards fluoride ion were found to be highly dependent on the position of the nitro substituent in the aromatic backbone. While the ortho and para nitro-substituted receptors showed intense colour change and associated colorimetric response upon addition of fluoride, the meta derivative did not provide any visible deviation in colour as well as colorimetric behaviour. Further, due to the presence of H-bond acceptor motif, the receptor-fluoride complexes formed by both ortho and para nitro-substituted derivatives are reasonably labile and dissociate to automatically result in the free receptor species within a short time span. This allowed reuse of the receptor solution for selective and successive recognition of fluoride by colorimetric technique without any external trigger.

Protocol for the Incorporation of γ-Amino Acids into Peptides: Application to (−)-Shikimic Acid Based 2-Amino-Methylcyclohexanecarboxylic Acids

“…Herein we report the first synthesis of polyhydroxylated 2-aminomethylcyclohexane carboxylic acids from (−)-shikimic acid, a suitable starting material, on account of its convenient structural properties: a cyclohexane ring bearing an α,β-unsaturated carboxylic acid moiety and three hydroxy substituents with well-defined spatial orientations . Our synthetic plan involved a Michael addition of nitromethane to an alkyl shikimate, followed by reduction of the nitro group of the resulting 2-nitromethylcarboxylic acids to amino. ,, A proper protocol for the incorporation of 2-aminomethylcyclohexanecarboxylic acids into peptides was also developed.…”