Highly potent anti-inflammatory, analgesic and antioxidant activities of 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine thiones.

Four series of tetrahydro-2H-1,3,5-thiadiazine-2-thiones (series A and B including two novel enantiopure isomers), tetrahydro-2H-1,3,5-thiadiazine-6-thiones (series C) and N-3 ester derivatives of tetrahydro-2H-1,3,5-thiadiazine-6-thiones (series D) were synthesized and evaluated for their anti-inflammatory, analgesic and anti-oxidant activities. These THTT analogues specially series D were first time examined for their in vitro anti-inflammatory, in vivo analgesic and anti-oxidant activities. Among them lipophilic compounds (series B and D) were found to be highly active for anti-inflammatory evaluation with IC50 values between 5.1-16.9 and 4.1-32.4 µM, respectively when compared with the standard drug ibuprofen IC50 = 11.2 µM. The structure-activity relationship exposed the importance of lipophilic substituents especially ester and n-propyl group for inhibition of inflammation. The molecular docking studies demonstrated that all the active analogues of THTT have notable binding relations with Arg120 of the active sites of COX-1 enzyme either through CS moiety of the THTT nucleus or with COO attached at N-3 of THTT nucleus. In vivo analgesic activity of the selected THTT compounds 14, 17, 18, 19 (series B) and 28 (series D) were also carried out by acetic acid-induced writhing procedure. The compound 28 showed significant anti-nociceptive/analgesic activity at the oral dose of 5 mg/kg body weight with the percent protection (32.05 %) when compared with standard indomethacin at 10 mg/kg (48.83 %). Additionally, these compounds demonstrated the moderate level of antioxidant potential with IC50 values in the range of 60.9 to 93.6 µM (standard butylated hyroxyanisole; IC50 = 44.2 µM). These results indicated that this class of heterocyclic compounds may be a template specially to design better anti-inflammatory and analgesic agents.

1,3,5-Thiadiazinane thione derivatives as significant urease inhibitors.

We report the promising urease inhibitory activity of four sets of tetrahydro thiadiazine thiones (THTT) namely 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine thiones: THTT 5-8 (set A) having alkyl/aryl substituents at N-3 and N-5 positions; THTT 9-12 (set B) and THTT 13-14 (set C) with 3-carboxylic acid derivatives and tetrahydro-2H-1,3,5-thiadiazine-6-thione esters 15-16 (set D). Gratifyingly, all four sets of THTT were recognized as promising inhibitors of urease enzyme. Among 12 tested compounds; THTT 6, 8, 10, 14 and 15 from each set respectively, demonstrated significant urease inhibitory activity with IC50 values between 11.2-29.8µM which is mostly found higher than that for thiourea, a standard urease inhibitor with IC50 value of 22.4µM. Furthermore, compound 7 showed almost the same level of inhibition (IC50 = 22.5µM) as of standard. In addition, molecular docking study supported the phenomenon that thiadiazinane ring itself is an active pharmacophore that binds through CH2 groups and S atom via carbon-hydrogen/π-sulfur interactions respectively to the active site of the urease enzyme. The optimistic results from this study suggest the use of thiadiazinane skeleton as a guided template for the advancement of new urease inhibitors in drug discovery.

Synthesis of dihydropyrimidine stabilized silver nanoparticles with significant anti urease and catalytic applications.

We synthesized and explored biological and environmental applications of novel silver nanoparticles (AgNps) stabilized by short chain heterocyclic thiol namely Ethyl 6-methyl-4-phenyl-2-thioxo1,2,3,4-dihydropyrim-idine-5-carboxylate (DHPM). Dihydropyrimidines (DHPM), a biological active class of compounds that contain a single thiol group at the focal point which strongly stabilized the nascent AgNps. The short alkyl chain of (DHPM) effectively controlled the growth kinetics and surface morphology of AgNps. The synthesized Dihydropyrimidine stabilized silver nanoparticles (DHPM-AgNps) were investigated using Ultraviolet- visible spectroscopy (UV-Vis), Atomic force Microscopy (AFM) and Fourier-transform infrared spectroscopy (FTIR). AFM exhibited the size and shape of the DHPM-AgNps with an average diameter of 10 ± 1 nm. Our prepared DHPM-AgNps were examined for urease enzyme inhibition activity. The synthesized DHPM-AgNps showed significant level of urease inhibition activity (% of inhibition 40.3±0.28%) when compared with standard thiourea inhibition activity (% of inhibition value 79.6± 0.47%.). Moreover prepared DHPM-AgNps system successfully applied for the reduction of para-nitrophenol (p-Nip). It reduces the para-nitrophenol (p-Nip) to para-aminophenol (p-Amp) within one second in the presence of NaBH4 under ambient temperature and pressure conditions, which followed the pseudo-first-order rate kinetics. This study will provide useful guidelines for designing efficient catalysts and stabilizing agents for Silver Nanoparticles.

1-Phenyl ethyl substituted tetrahydro-2H-1,3,5-thiadiazine-2-thione derivatives as promising antimicrobial agents.

Seven derivatives of 1-phenyl ethyl group containing 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine-thiones (THTT) were prepared and examined for their antibacterial and antifungal properties by using Microplate Alamar Blue Assay (MABA) and agar tube dilution protocol respectively. In vitro antifungal potential was investigated against five human pathogens and compared with the standard drugs amphotericin B and miconazole. In vitro antibacterial activity was investigated against four pathogens and compared with the ofloxacin. All compounds exhibited very promising antifungal activities against all tested pathogens. Structure activity relationship showed the importance of the presence of 1-phenyl ethyl substituent at N-3 of THTT nucleus for antifungal effects. However, these compounds showed significant antibacterial activity only against S. aureus. The compound 6c of the series was found most active compound that displayed promising antifungal potential against all tested pathogens [Growth Inhibition (GI) = 100%], and also showed promising antibacterial potential against S. aureus (GI% = 83.49) which is very much closer to the standard ofloxacin (GI% = 88.05). The study may be useful in the development of improved antimicrobial agents.

Natural products based crown ethers: synthesis and their anticancer potential.

Natural products based novel crown ethers have been prepared by employing biologically active natural structures including tetrahydroisoquinoline, chrysin and biochanin-A as the side arms. The resulting crown scaffolds were evaluated for their anticancer potential against two cancer cell lines i.e. NCI-H460 (non-small lung carcinoma), MCF-7 (breast adenocarcinoma). The comparative study showed that the addition of crown scaffold put marked effects on antiproliferative profile of parent natural precursors and is significant for lung carcinoma in particular. Biochanin-A derived crown ether showed three (03) folds higher antiproliferative activity (IC50 = 6.08 ± 0.07 µM) against lung carcinoma as compared to standard drug cisplatin (IC50 = 19.00 ± 1.24 µM). Cytotoxic trends for NIH-3T3 cell lines were also examined and found reduced as compared to parent natural structures. Hence, these findings could open a new pathway towards developing effective carcinostatic drugs.HIGHLIGHTSFour natural products based novel crown ethers have been developed.Comparative antiproliferative screening of crown ethers and natural precursors.Addition of crown showed marked effects on anticancer profile of natural products.Crown formation is significant for lung carcinoma potential in particular.Biochanin-A derived crown ether found three folds more active than standard drug.

Natural products embedded crown ethers as potent insulin secretory agents.

Natural products embedded crown ethers were prepared by utilizing bioactive natural products including chrysin, tetrahydroisoquinoline (THIQ), and biochanin-A. The prepared crown ether scaffolds were evaluated and compared with their natural product precursors for insulin secretory activity on isolated mice islets and for their fluorescent properties. All the crown adducts were found more active as compared to their natural product precursors. Bischrysin 32-crown-10 (6d), THIQ 15-Crown-5 (6a) and chrysin 16-crown-5 (6c) showed mild, moderate and strong insulin secretory activity, respectively when compared with the standard drug tolbutamide (TB). Particularly crown derivative 6c showed strong activity (31.10 ng/islet/h) that is almost two (02) fold higher than that of standard drug TB (16.82 ng/islet/h). To the best of our knowledge crown ethers based antidiabetic study is being reported for the first time in literature through this work. Furthermore, fluorescence study showed the significant increase in absorption and emission maximum (hypsochromic effect) in crown structures when compared with their natural product precursors. Present optimistic results obtained from this study may be a guided template for developing new effective insulin secretory agents.

Antiproliferative activity of 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine thione (THTT) derivatives and evaluation as potential prodrug.

Four series of tetrahydro-2H-1,3,5-thiadiazine thione derivatives were screened for their in vitro antiproliferative activities against two human cancerous PC3 and HeLa cell lines. The cytotoxicity of all the compounds (series A-D) was also determined on mammalian mouse fibroblast 3T3 cells. Most of the compounds showed significant anticancer potential against both cancer cell lines within the range of IC50 = 6.4-29.9 and 2.4-23.8 M respectively when compared with standard doxorubicin (IC50 = 0.3 M). All compounds demonstrated a notable selectivity for Hela cells and found either non-toxic or relatively less toxic for 3T3 cell lines model. The structure-activity relationship indicated that antiproliferative activity mainly influenced by the nature and position of substituents at thidiazine nucleus. In general, the presence of aryl groups for example 3,4-(OMe) 2.Bzl and CH(Ph)Me at N-3 position resulted in a significant activity. Under enzymatic hydrolysis, complete conversion (100%) of ester derivative of thiadiazine thione (10a) into its acidic counterpart (7c) was achieved during 20 min which indicated that these types of THTT ester derivatives can be a possible lead for future investigations as prodrug anticancer probes.

New series of 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine thione (THTT) derivatives: Synthesis and potent antileishmanial activity.

Four series of heterocyclic compounds, namely, tetrahydro-2H-1,3,5-thiadiazine thione derivatives were synthesized in good to excellent yields and were screened for their in vitro antileishmanial activities against Leishmania major (promastigotes). Most of the compounds showed significant antileishmanial activity within the range of IC50 = 15.48-39.36 µM when compared with standard pentamidine (IC50 = 14.95 µM). The structure-activity relationship showed that N-3 and N-5 substituents have a key role against leishmanicidal activity. The ester analogues (series B) were found to have a 1.5 to 5-fold reduced activity compared to their acidic counterparts. Cytotoxicity against mammalian mouse fibroblast 3 T3 cells was also evaluated and compared between the acid and its ester analogue. The reduction of antileishmanial activity and loss of toxicity in the newly developed THTT ester derivative indicates that these compounds can be used as a template study for the production of effective antileishmanial ester prodrugs.

Dihydropyrimidine based hydrazine dihydrochloride derivatives as potent urease inhibitors.

Four series of heterocyclic compounds 4-dihydropyrimidine-2-thiones 7-12 (series A), N,S-dimethyl-dihydropyrimidines 13-18 (series B), hydrazine derivatives of dihydropyrimidine 19-24 (series C), and tetrazolo dihydropyrimidine derivatives 25-30 (series D), were synthesized and evaluated for in vitro urease inhibitory activity. The series B-D were first time examined for urease inhibition. Series A and C were found to be significantly active with IC50 values between 34.7-42.9 and 15.0-26.0 µM, respectively. The structure-activity relationship showed that the free S atom and hydrazine moiety are the key pharmacophores against urease enzyme. The kinetic studies of the active series A (7-12) and C (19-24) were carried out to determine their modes of inhibition and dissociation constants Ki. Compounds of series A (7-12) and series C (19-24) showed a mixed-type of inhibition with Ki values ranging between 15.76-25.66 and 14.63-29.42 µM, respectively. The molecular docking results showed that all the active compounds of both series have significant binding interactions with the active sites specially Ni-ion of the urease enzyme. Cytotoxicity of all series A-D was also evaluated against mammalian mouse fibroblast 3T3 cell lines, and no toxicity was observed in cellular model.

Palladium(0)-catalyzed, copper(i)-mediated coupling of cyclic thioamides with alkenylboronic acids, organostannanes, and siloxanes.

The Pd-catalyzed cross-coupling of cyclic thioamides and thioureas with alkenylboronic acids, vinyl- and (het)arylstannanes, and arylsiloxanes in the presence of stoichiometric amounts of a Cu(I) cofactor is described. The desulfitative C-C cross-coupling protocol of the Liebeskind-Srogl type is performed under neutral conditions and can be applied to a range of heterocyclic structures with embedded thioamide fragments. Employing controlled microwave irradiation at 100 degrees C utilizing either a single-mode reactor or a multimode parallel reaction platform, cross-couplings can generally be completed within 1-3 h and proceed in good yields.

Synthesis of bisquinolone-based mono- and diphosphine ligands of the Aza-BINAP type.

Mono- and bisphosphine ligands based on the 4,4'-bisquinolone structural framework (BIQUIP ligands) were generated by direct microwave-assisted palladium-catalyzed carbon-phosphorus cross-coupling reactions employing the corresponding heteroaryl bromides and diphenylphosphine as substrates.

Symmetrical bisquinolones via metal-catalyzed cross-coupling and homocoupling reactions.

Functionalized 4,4'-bisquinolones can be efficiently synthesized by microwave-assisted palladium(0)-catalyzed one-pot borylation/Suzuki cross-coupling reactions or via nickel(0)-mediated homocouplings of 4-chloroquinolin-2(1H)-one precursors. Both methods are also applicable to other types of symmetrical biaryls.