BITS Faculty Publications
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Item Copper-catalysed Csingle bondN/Csingle bondO coupling in water: a facile access to N-coumaryl amino acids and fluorescent tyrosine & lysine labels(Elsiever, 2016-06) Bajaj, Kiran; Sakhuja, RajeevA mild, efficient, ligand free and environmentally benign approach towards the construction of sp2 C-sp3 N bond has been developed via copper catalysed Ullmann type of coupling between 4-chlorocoumarin with N-terminus unprotected amino acids in microwave-aqua conditions, yielding a series of N-coumaryl amino acids in good to excellent yields. Excellent photo-physical properties exhibited by these N-coumaryl amino acids and their chemical applicability as C-terminus coupling partners for N-terminus peptides make them potential fluorescent probes in labelling studies. The methodology was extended towards the Csingle bondO and Csingle bondN coupling for the synthesis of fluorescent coumaryl labelled tyrosine and lysine labels respectively. Application of coumaryl labelled tyrosine was further explored towards the synthesis of fluorescent labelled opioid tetrapeptide, Endomorphin-2 derivative.Item Efficient Syntheses of Naphthoquinone-Dipeptides(Thieme, 2010) Sakhuja, RajeevNaphthoquinone-dipeptides are synthesized in 76-89% yield from naphthoquinone-amino acid conjugates by N-acylbenzotriazole methodology in aqueous media at 20 ˚CItem Copper-catalysed Csingle bondN/Csingle bondO coupling in water: a facile access to N-coumaryl amino acids and fluorescent tyrosine & lysine labels(Elsiever, 2016-06-22) Sakhuja, Rajeev; Bajaj, KiranA mild, efficient, ligand free and environmentally benign approach towards the construction of sp2 C-sp3 N bond has been developed via copper catalysed Ullmann type of coupling between 4-chlorocoumarin with N-terminus unprotected amino acids in microwave-aqua conditions, yielding a series of N-coumaryl amino acids in good to excellent yields. Excellent photo-physical properties exhibited by these N-coumaryl amino acids and their chemical applicability as C-terminus coupling partners for N-terminus peptides make them potential fluorescent probes in labelling studies. The methodology was extended towards the Csingle bondO and Csingle bondN coupling for the synthesis of fluorescent coumaryl labelled tyrosine and lysine labels respectively. Application of coumaryl labelled tyrosine was further explored towards the synthesis of fluorescent labelled opioid tetrapeptide, Endomorphin-2 derivative.Item Amino acid appended cholic acid–azobenzene dyad: an effective & smart phase selective gelator for aromatic solvents(RSC, 2016) Sakhuja, RajeevA series of amino acid appended cholic acid–azobenzene dyads have been synthesized and studied for their gelation behaviour. One of the L-alanine based dyads showed excellent gelation behaviour in a variety of solvents at room temperature with minimum gel concentration in the range 0.8% (w/v)–1.8% (w/v). The morphology of the stable gels indicated the formation of a lamellar or a dense sheet network in different solvents. Variable temperature 1H-NMR and FT-IR studies revealed an evident role of intermolecular hydrogen bonding in the self-assembly process. The photo-isomerization between the trans and cis forms of the azobenzene unit was established by UV-visible spectroscopy, and a comparison of 1H NMR and SEM images of the gel and sol forms. In addition, π → π stacking between phenyl groups of azobenzene might have provided an additional driving force for the formation of a dense three-dimensional network capable of phase selective gelation of aromatic solvents from a water/solvent mixture. This selective gelation of aromatic solvents remains unaffected even in the presence of the common salts usually present in water from different sources. The phase selective gelation ability of the dyad was successfully explored towards the removal of toxic fat-soluble rhodamine dye from water and selectively gelatinizing petrol and crude oil from an oil/water mixture at room temperature. Thus, these smart systems possess the potential to be used effectively in water purification and oil-spill remediation.