Formation of Periodic γ‐Turns in α/β‐Hybrid Peptides: DFT and NMR Experimental Evidence

Hybrid peptidic oligomers comprising natural and unnatural amino acid residues that can exhibit biomolecular folding and hydrogen‐bonding mimicry have attracted considerable interest in recent years. While a variety of hybrid peptidic helices have been reported in the literature, other secondary structural patterns such as γ‐turns and ribbons have not been well explored so far. The present work reports the design of novel periodic γ‐turns in the oligomers of 1:1 natural‐α/unnatural trans‐β‐norborenene (TNAA) amino acid residues. Through DFT, NMR, and MD studies, it is convincingly shown that, in the mixed conformational pool, the heterogeneous backbone of the hybrid peptides preferentially adopt periodic 8‐membered (pseudo γ‐turn)/7‐membered (inverse γ‐turn) hydrogen bonds in both polar and non‐polar solvent media. It is observed that the stereochemistry and local conformational preference of the β‐amino acid building blocks have a profound influence on accessing the specific secondary fold. These findings may be of significant relevance for the development of molecular scaffolds that facilitate desired positioning of functional side‐chains.     

Synthesis and Antimicrobial Activity of Amido Sulfonamido Methane Linked Bisoxazoles,Bisthiazoles, and Bisimidazoles

A new class of amido sulfonamido methane linked bisoxazoles, bisthiazoles, and bisimidazoles were prepared adopting simple and versatile synthetic methodologies. The lead compounds were assayed for antimicrobial activity.     

A smooth access to benzotriazoles via azide-benzyne cycloaddition

A facile synthesis of 1-alkyl benzotriazoles is achieved through fluoride triggered azide-benzyne cycloaddition. Various alkyl azides were treated with 2-(trimethylsilyl) phenyl triflate in the presence of CsF in acetonitrile to afford the corresponding substituted benzotriazoles in good yield.     

Synthesis of some sulfur-containing spiro-pyrimidinetriones,pyrazolidinediones, and isoxazolidinediones

Novel sulfur-containing spiro compounds such as 7,11-diaryl-9-thia-2,4-diazaspiro [5,5] undecane-1,3,5-trione 9,9-dioxides ( 2 ), 6,10-diaryl-8-thia-2,3-diazas-piro[4,5]decane-1,4-dione-8,8-dioxides ( 3 ) and 6,10-diaryl-2-oxo-8-thia-3-azaspiro [4,5] decane-1,4-dione-8,8-dioxides ( 5 ) have been prepared by the condensation of 4-dimethoxycarbonyl/diethoxycarbonyl-3,5-diaryl-1-thiane 1,1-dioxides ( 1 ) with urea, hydrazine hydrate, and hydroxylamine hydrochloride, respectively. The N-substituted derivatives ( 4 and 6 ) of 3 and 5 have also been prepared by acylation and nitrosation. The structures of 2, 3 , and 5 were established by IR, ¹H NMR, and ¹³C NMR spectral studies, respectively.     

Synthesis and Antimicrobial Activity of a New Class of Sulfonylmethane Linked Bisheterocycles

A new class of sulfonylmethane linked bisheterocycles were prepared and studied their antimicrobial activity.     

Synthesis of Amido‐linked Oxazolyl/Thiazolyl/Imidazolyl Pyrazoles and Isoxazoles

The amido‐linked oxazolyl/thiazolyl/imidazolyl pyrazoles and isoxazoles were prepared from the synthetic intermediates oxazolyl/thiazolyl/imidazolyl acrylamides adpoting1,3‐dipolar cycloaddition of nitrile imines and nitrile oxides.     

Intramolecular copper(I)-catalyzed 1,3-dipolar cycloaddition of azido-alkynes: synthesis of triazolo-benzoxazepine derivatives and their biological evaluation

Synthesis of a series of [1,2,3] triazolo [5,1-c] [1,4]benzoxazepine derivatives have been accomplished by the intramolecular Cu(I)-catalyzed cycloaddition of azido-alkynes derived from salicylaldehyde. The biological profile of these heterocyclic structural scaffolds toward anti-bacterial as well as anti-fungal activity has also been illustrated.