Synthesis of carpachromene and related isopentenylated derivatives of apigenin

Acacetin (4) on reaction with prenyl bromide in the presence of methanolic sodium methoxide yielded 6,8-di-C-prenyl-(5) and 6-C-prenyl-(10) derivatives. The former (5) formed the corresponding bisdihydropyrano derivative (8). Monomethyl derivative of 10 (12) gave monodihydropyrano derivative (13). DDQ reaction of 10 followed by methylation afforded di-O-methyl carpachromene (2); whereas that of 5 gave a mixture of 21 and 22.

Nuclear prenylation of apigenin (3) in a similar way gave 6,8-di-C-C-prenyl-(16), its 7-0-prenyl-(15) and 6-C-prenyl-(18) derivatives. DDQ reaction of 18 provided natural carpachromene.¹ The structure of the isopentylated apigenin isolated by Dreyer et al.² needs further consideration.     

Identification of Druggable Targets for Acinetobacter baumannii Via Subtractive Genomics and Plausible Inhibitors for MurA and MurB

Emergence of the multidrug-resistant pathogens has rendered the current therapies ineffective thereby, resulting in the need for new drugs and drug targets. The accumulating protein sequence data has initiated a drift from classical drug discovery protocols to structure-based drug designing. In the present study, in silico subtractive genomics approach was implemented to find a set of potential drug targets present in an opportunist bacterial pathogen, Acinetobacter baumannii (A. baumannii). Out of the 43 targets identified, further studies for protein model building and lead-inhibitor identification were carried out on two cell-essential targets, MurA and MurB enzymes (of A. baumannii designated as MurA_Ab and MurB_Ab) involved in the peptidoglycan biosynthesis pathway of bacteria. The homology model built for each of them was further refined and validated using various available programs like PROCHECK, Errat, ProSA energy plots, etc. Compounds showing activity against MurA and MurB enzymes of other organisms were collected from the literature and were docked into the active site of MurA_Ab and MurB_Ab enzymes. Three inhibitors namely, T6361, carbidopa, and aesculin, showed maximum Glide score, hydrogen bonding interactions with the key amino acid residues of both the enzymes and acceptable ADME properties. Furthermore, molecular dynamics simulation studies on MurA_Ab–T6361 and MurB_Ab–T6361 complexes suggested that the ligand has a high binding affinity with both the enzymes and the hydrogen bonding with the key residues were stable in the dynamic condition also. Therefore, these ligands have been propsed as dual inhibitors and promising lead compounds for the drug design against MurA_Ab and MurB_Ab enzymes.     

One-Pot Synthesis and Fungicidal Activity of Pyrimidinylidenamido- and Thiazolinylidenamidomonothiophosphoric Esters

A novel one-pot synthesis of four new classes of amidothiophosphoric esters and trisamidothiophosphoric esters is developed. (1-Alkyl-2-pyrimidinylidenamido)bis(diethylamido)thiophosphates, (1-alkyl-2-pyrimidinylidenamido)bis (O-2/4-methylphenyl)thiophosphates, (3-alkyl-2-thiazolinylidenamido)bis (diethylamido)thiophosphate and (3-alkyl-2-thiazolinylidenamido)bis(O-2/4-methylphenyl)thiophosphates are obtained from the nucleophilic substitution and oxidation of N-alkyl-2-cycloiminylidenaminodichlorophosphines generated in situ from the reaction of the corresponding N-alkyl-2-aminocycloiminium halide with phosphorus trichloride and triethylamine. The synthesized thiophosphoric esters have been investigated for fungicidal properties.     

SYNTHESIS AND SEMIEMPIRICAL CALCULATIONS OF THIAZOLIDINONE AND IMIDAZOLIDINONE DERIVATIVES OF α-DIONES

The condensation reactions of α-diones with rhodanine and creatinine to give acenaphthylidene, isatylidene and thioisatylidene derivatives, which may act as potential bioactive compounds, are described. The synthesized compounds have been characterized by elemental analysis and spectral studies, as well as by molecular modelling using PCWIN model.     

Highly Selective and Sensitive Graphene Based Electrochemical Sensor for Quantification of Receptor Agonist Rizatriptan

A highly selective and sensitive electrochemical sensor has been developed by modification of a glassy carbon electrode (GCE) with graphene (GRP) for quantification of Rizatriptan. The significant increase of the peak current and the improvement of the oxidation peak potential indicate that the electrochemical sensor facilitates the electron transfer of Rizatriptan. The oxidation peak current was proportional to the Rizatriptan concentration in the range from 100 to 600 µg/mL with detection (LOD) and quantification limit (LOQ) of 36.52 and 121.73 µg/mL, respectively. The developed method was successfully employed for quantification of Rizatriptan in pharmaceutical formulations. The sensor shows great promise for simple, sensitive and quantitative detection of Rizatriptan.     

A Rapid and Facile Esterification of Na-Carboxylates with Alkyl Halides Promoted by the Synergy of the Combined Use of DMSO and an Ionic Liquid Under Ambient Conditions

The synergy of the combined use of DMSO and an ionic liquid viz. (bbim)⁺Br^? has brought about a rapid and efficient esterification of sodium carboxylates with acyl and alkyl halides under ambient conditions in excellent isolated yields (90–95%) in short reaction times (12–40 min).     

Scrupulous recognition of biologically important acids by fluorescent “turn off-on” mechanism of thaicalix reduced silver nanoparticles

Water dispersible silver nanoparticles(AgNps) were prepared using thiacalix[4]arene tetrahydrazide(TCTH) as a reducing and stabilizing agent.TCTH-AgNps were characterized by surface plasmon resonance(SPR),transmission electron microscopy(TEM) and energy dispersive X-ray(EDX).Relatively uniform 20 nm spherical particles of TCTH-AgNps were efficiently formed over a pH range of 5-9 and from 10-40 ℃.The interaction behavior of TCTH-AgNps with different amino acids was investigated using spectrophotometry and spectrofluorimetry.Among the amino acids tested,only tryptophan and histidine showed fluorescence quenching and fluorescence enhancement,respectively.The linear detection range by Stern-Volmer plot was 5 nmol/L to 0.48 μmol/L for tryptophan and 4 nmol/L to 0.54 μmol/L for histidine.TCTH-AgNps were able to effectively reduce the levels of gram-positive bacteria,gram-negative bacteria,and fungi.These properties argue for the potential use of TCTH-AgNps as detectors of histidine and tryptophan and as antibiotics.     

Efficient Transition‐Metal‐Free Oxidation of Benzylic and Secondary Alcohols to the Carbonyl Compounds Using an N‐Bromosuccinimide/NH4Cl System

The oxidation of a variety of benzylic and secondary alcohols was achieved in excellent yields using an NBS/NH₄Cl system in aqueous acetonitrile (CH₃CN‐H₂O; 7/3 v/v) at 80°C under very mild conditions.     

Rapid Suzuki‐Miyaura cross‐coupling reaction catalyzed by zirconium carboxyphosphonate supported mixed valent Pd(0)/Pd(II) catalyst

Mixed valent Pd(0)/Pd(II) nano‐sized aggregates supported onto a chemically robust layered zirconium carboxyphosphonate framework is prepared and its catalytic activity in Suzuki‐Miyaura cross coupling reaction is explored. The exceptionally high catalytic efficacy of the heterogeneous catalyst in Suzuki‐Miyaura cross coupling reaction is signified by remarkably short reaction time 2 minutes and high turnover frequency of 1.3 x 10⁴ hr^?1. The catalyst can be recycled several times without significant loss of catalytic efficacy, while spectroscopic, structural and microscopic investigations suggest the integrity of the catalyst even after fifth catalytic cycle. The unique ability of the zirconium carboxyphosphonate framework to interact strongly with palladium in dual Pd(0)/Pd(II) oxidation states has been attributed to this remarkable augmentation of catalytic efficacy.