An efficient and highly stereoselective synthesis of novel trifluoromethylated trans-dihydrofuro[2,3-c]pyrazoles using arsonium ylides

2,4-Diamino-5-(5-hydroxy-1-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-5H-chromeno[2,3-b]pyridine-3-carbonitrile

5H-Chromeno[2,3-b]pyridines are important compounds with industrial, biological, and medicinal properties. In this short note, the multicomponent reaction of salicylaldehyde, malononitrile dimer, and 2-phenyl-5-(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one in dimethyl sulfoxide at ambient temperature was investigated to give 2,4-diamino-5-(5-hydroxy-1-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)-5H-chromeno[2,3-b]pyridine-3-carbonitrile with good yield. The structure of the previously unknown chromeno[2,3-b]pyridine derivative was confirmed by elemental analysis, mass, nuclear magnetic resonance, and infrared spectroscopy data. The ADME (absorption, distribution, metabolism, and excretion) properties were also assessed.

Recent developments in the synthesis and applications of furopyrazoles

This review aims to describe the different strategies developed so far for the synthesis of furopyrazoles and their biological and pharmacological properties.

Domino Reaction of Pyrrolidinium Ylides: Michael Addition/[1,2]-Stevens Rearrangement

A novel domino reaction featuring a Michael addition/[1,2]-Stevens rearrangement reaction of pyrrolidinium ylides with electrophilic alkenes is described. Ylides generated under mild conditions from 2-aryl- N-cyanomethyl- N-methylpyrrolidinium salts entered the Michael addition, followed by a [1,3]-hydrogen shift and finally the [1,2]-Stevens rearrangement to give 3-aryl-2-cyano-2-(2-EWG-ethyl)-1-methylpiperidines.

Structure-activity relationships in a new class of non-substrate-like covalent inhibitors of the bacterial glycosyltransferase LgtC

Lipooligosaccharide (LOS) structures in the outer core of Gram-negative mucosal pathogens such as Neisseria meningitidis and Haemophilus influenzae contain characteristic glycoepitopes that contribute significantly to bacterial virulence. An important example is the digalactoside epitope generated by the retaining α-1,4-galactosyltransferase LgtC. These digalactosides camouflage the pathogen from the host immune system and increase its serum resistance. Small molecular inhibitors of LgtC are therefore sought after as chemical tools to study bacterial virulence, and as potential candidates for anti-virulence drug discovery. We have recently discovered a new class of non-substrate-like inhibitors of LgtC. The new inhibitors act via a covalent mode of action, targeting a non-catalytic cysteine residue in the LgtC active site. Here, we describe, for the first time, structure-activity relationships for this new class of glycosyltransferase inhibitors. We have carried out a detailed analysis of the inhibition kinetics to establish the relative contribution of the non-covalent binding and the covalent inactivation steps for overall inhibitory activity. Selected inhibitors were also evaluated against a serum-resistant strain of Haemophilus influenzae, but did not enhance the killing effect of human serum.

Pd-catalyzed asymmetric hydrogenation of fluorinated aromatic pyrazol-5-ols via capture of active tautomers

An efficient palladium-catalyzed asymmetric hydrogenation of fluorinated aromatic pyrazol-5-ols has been developed via capture of the active tautomers. A wide variety of 2,5-disubstituted and 2,4,5-trisubstituted pyrazolidinones have been synthesized with up to 96% and 95% ee, respectively. The hydrogenation pathway includes Brønsted acid promoted tautomerization of pyrazol-5-ols and Pd-catalyzed asymmetric hydrogenation of the active tautomer.