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A series of 21 sulfoester and sulfonamide derivatives comprising two aromatic rings was synthesized to investigate the effect of the presence of either electron-donating (ED) or electron-withdrawing (EW) groups on the intramolecular π-stacking assembly. The positioning of ED or EW moieties was carried out directly on one of the aromatic rings linked to the sulfonyl or sulfonamide moieties. In contrast, the other aromatic ring (phenyl or pyridine) was connected by a –CH2–CH2– spacer with the sulfonyl or sulfonamide moiety. The purpose of having an ethyl spacer between the two aromatic rings was to achieve conformational flexibility, facilitating the intramolecular π-stacking assembly between the two aromatic rings. The use of sulfoester/sulfonamide groups allowed more conformational flexibility to attain desired orientations in solids with the interplay of the hydrogen-bonding interactions. Between the two functional groups, sulfonamides offered a more hydrogen-rich environment due to the amine moiety and may exhibit higher H-bonding propensity than the sulfoester moiety. The central idea here was to study the interplay between the hydrogen-bonding and π⋯π interactions. The substituent groups chosen were categorized as strong electron-withdrawing (–CF3 and –CN), weak electron-withdrawing (–Cl and –Br), neutral (–H), and good electron-donating (–CH3 and –OCH3) groups. Crystal structure analysis revealed the syn conformation for all the derivatives, enabling intramolecular π⋯π interactions between the two aromatic rings, whereas in the sulfonamide derivatives, the molecule takes either midway or anti conformations, except for one pyridine sulfonamide derivative, which showed the syn orientation but lacked intramolecular π-stacking interactions. The absence of any conventional H-bond forming functional groups in the sulfoester derivatives may have resulted in the syn geometry facilitated by intramolecular π-stacking interactions. Conversely, H-bond-forming functional groups in the sulfonamide derivatives could have prevented the syn conformation. The conformational analysis carried out employing density functional theory (DFT) calculations confirmed the higher stability of the syn conformation over the midway and anti orientations. [ABSTRACT FROM AUTHOR]

The '2R,4R'‐2‐aryl thiazolidine‐4‐carboxylic acid anilides (ATCAAs) were synthesized using cyanuric chloride (CC) as a clean and substoichiometric acid‐amine coupling agent under optimized reaction conditions. The diesterphenol intermediate based mechanism is proposed and supported by spectral characterization of the intermediate. The single crystal X‐ray structures of acid substrate (2R,4R)‐3‐(tert‐butoxycarbonyl)‐2‐(2‐methoxyphenyl)thiazolidine‐4‐carboxylic acid (3 a) and anilides (R)‐tert‐butyl 4‐(2‐fluorophenylcarbamoyl)thiazolidine‐3‐carboxylate (4 b), (2R,4R)‐tert‐butyl 2‐(2,6‐dichlorophenyl)‐4‐(m‐tolylcarbamoyl)thiazolidine‐3‐carboxylate (6 b) confirmed the formation of chiral anilides. The synthesized library of anilides [(R)‐tert‐butyl 4‐Aryl thiazolidine‐3‐carboxylate and (2R,4R)‐tert‐butyl 2‐Aryl‐4‐Aryl thiazolidine‐3‐carboxylate] 4 a‐6 f was screened for their in vitro anti cancer, neuronal and neuroprotective studies. The anilides 4 b, 4 g, 5 d, 5 h, 6 c and 6 f (where the aryl=2‐fluorophenylcarbamoyl, 4‐chlorophenylcarbamoyl, 2‐methoxyphenyl, 2,5‐dichlorophenylcarbamoyl, 2,6‐dichlorophenyl, 4‐chlorophenylcarbamoyl respectively)were found to be less cytotoxic towards N2 A, SHSY‐5Y neuronal cell lines in their differentiated and undifferentiated forms, and also exhibited dose dependant anti‐inflammatory properties for a possible identification towards neurodegenerative and inflammatory disorders. [ABSTRACT FROM AUTHOR]

A visible-light-promoted merged gold/photoredox catalyzed ipso-arylative cyclization has been reported. For instance, the reaction of aryl-alkynoates and N-arylpropiolamides with aryldiazonium salts in the presence of catalytic amounts of [(4-OCH3)C6H4]3PAuCl and Ru(bpy)3(PF6)2 under irradiation using a 32 W CFL bulb gave arylated spirocarbocycles in moderate to good yields. [ABSTRACT FROM AUTHOR]

In this paper, we provide structural insights into the hydrogen-bonding and folding pattern in Ant-Ant-Pro-Gly tetrapeptides (Ant: anthranilic acid; Pro: proline; and Gly: glycine). Comparison of the C-terminal esters and their amide analogs revealed strikingly different H-bonding networks. Whereas the ester analogs displayed an open structure without terminal Hbonding interactions, the amide analogs showed a completely folded structure. Structural details were revealed by using a combination of X-ray crystal structure studies and NOE-based molecular dynamics (MD) simulation studies. [ABSTRACT FROM AUTHOR]

Design and development of drugs in multi-drug resistant (MDR) infections have been of growing interest. We report the syntheses, and antibacterial and antifungal activities of imidazole-based 1,4-naphthoquinones (I-1 to I-4; 1-alkyl-2-methyl-1H-naphtho[2,3-d]imidazole-4,9-dione (alkyl = methyl to butyl)) and their precursors (B-3; N-(3-chloro-1,-dioxo-1,4-dihydronaphthalen-2-yl)acetamide) and A-1 to A-4; N-(3-(alkylamino)-1,4-dioxo-1,4-dihydronaphthalen-2-yl)acetamide (alkyl = methyl to butyl). Crystal structures of B-3, A-1 to A-3 and I-2 to I-4 were obtained through single crystal X-ray diffraction experiments. Electronic structure and charge distribution have further been characterized with the use of Density Functional Theory. Seven of these derivatives display a broad spectrum of antibacterial activity against few selected bacterial strains (Gram-positive and Gram-negative). As demonstrated MIC values with B-2 and B-3 against bacterial isolates were 8–64 μg ml−1 and those against pathogenic yeast, C. albicans, were observed in the range of 128–256 μg ml−1. MIC data of these derivatives suggest them to be promising against pathogens. [ABSTRACT FROM AUTHOR]

A co-operative Au(i)/Ag(i) catalyst system has been developed to utilize N-allenamides as nucleophilic enal equivalents for the interceptive capturing of incipient carbocations generated through π-acid-triggered imino-alkyne cyclization. The salient features include the in situ generation of silver-bound carbocations (from iminoalkynes), α-gold(i) enals (from N-allenamides) and union of these two species to form indolizines with the regeneration of Au and Ag catalysts. [ABSTRACT FROM AUTHOR]