Novel 1,3,4‐Oxadiazole Derivatives of Dihydropyrimidinones: Synthesis,Anti‐Inflammatory,Anthelmintic, and Antibacterial Activity Evaluation

The present study depicts synthesis of a series of some novel 5‐(5‐(aryl)‐1,3,4‐oxadiazol‐2‐yl)‐3,4‐dihydro‐6‐methyl‐4‐styrylpyrimidin‐2(1H)‐one derivatives. All the newly synthesized compounds were characterized by FTIR, ¹H NMR, ¹³C NMR, mass spectrometry, and elemental analysis. The compounds were evaluated for their in vivo anti‐inflammatory activity by the carrageenan‐induced rat paw edema method. The compounds were also screened for their anthelmintic activity on Indian earthworms and antibacterial activity against some gram positive and gram negative strains of bacteria. This pharmacological activity evaluation revealed that, among all the compounds screened, compounds 4b and 4c were found to have promising anti‐inflammatory activity. Interestingly, compounds 4b , 4c , and 4i exhibited appreciable anthelmintic property, while compounds 4c , 4g , and 4h showed leading antibacterial activity against the selected pathogenic strains of bacteria.     

Synthesis of Novel Tetrazole Containing Quinoline and 2,3,4,9‐Tetrahydro‐1H‐β‐Carboline Derivatives

This presentation describes the successful synthesis of novel tetrazole‐based quinoline and tetrahydro‐1H‐β‐carboline derivatives via one‐pot multicomponent reactions in moderate to good yields. These reactions have presumably proceeded through Ugi‐azide or Ugi‐azide/Pictet–Spengler processes, respectively.     

Synthesis of Conjugated Polyphenylene Dendritic β-Diketones

An efficient synthesis of high generation conjugated polyphenylene dendrimer-based β-diketones was investi- gated using simple synthetic methods. The new dendrimer-based β-diketones were characterized by NMR, MS and elemental analysis. The UV-Vis and fluorescence spectra of these β-diketones in different solvents were investigated The photoluminescent （PL） quantum yield and TG and DSC curves were also investigated. A new intermediate, 1-bromo-3,5-diiodobenzene, was developed to synthesize high generation dendrimers with good yields.     

Novel Synthesis of α‐Diketones from Bisbenzimidazolium Salt and Grignard Reagents

The reaction of bisbenzimidazolium salt with Grignard reagents and a new synthetic method of a‐diketones from bis‐benzimidazolium salt and Grignard reagents are reported. The structures of all a‐diketones are characterized by elemental analyses, infrared spectroscopy and ¹H NMR spectroscopy. The influences of the various Grignard reagents on the yield of a‐diketones and the mechanism are discussed, and a new convenient synthetic method for a‐diketones is provided.     

Isoxazolopyrimidinethione and Isoxazolopyridopyrimidinethione Derivatives: Key Intermediates for Synthesis of Novel Fused Triazoles as Potent 5α‐Reductase Inhibitors and Anti‐Prostate Cancer

The arylideneisoxazolone derivative 1 is used for preparation of two different pyrimidinethiones 3 and 5 through interaction with thiourea and thiouracil, respectively. Compounds 3 and 5 were subjected to reaction with different hydrazonyl halides in basic medium to afford different triazolopyrimidines 9a , 9b , 9c , 9d , 9e , 9f , 9g , 9h and 13a , 13b , 13c , 13d , 13e , 13f , the structures were confirmed by their spectral and elemental analysis. All the newly synthesized products were screened against 5α‐reductase. Some of the newly synthesized compounds showed potent 5α‐reductase inhibition activities with good ED₅₀.     

Synthesis and Crystal Structure of Novel β‐Lactam Derivatives Bearing Quinoline Moiety via [2 + 2] Cycloaddition

A series of new β‐lactam derivatives 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l were synthesized from [2 + 2] cycloaddition reaction of imines containing quinoline moiety 3a , 3b , 3c , 3d , 3e , 3f with ketene generated in situ from chloroacetyl chloride in dry Et₃N. The structures of the prepared compounds were characterized by IR, MS, ¹H NMR, and elemental analysis. In addition, the structure of ( 4i ) was determined by single crystal X‐ray crystallography.     

Catalyst‐free Multicomponent Synthesis of β‐Mercapto Diketones in Water

A simple, efficient and eco‐friendly route has been developed for the synthesis of β‐mercapto diketones via a multicomponent reaction of an aldehyde, acetylacetone and thiol in water. This methodology affords a number of β‐mercapto diketone derivatives in moderate to good yields.     

Preparation of β2‐Homotryptophan Derivatives for β‐Peptide Synthesis

In view of the prominent role of the 1H‐indol‐3‐yl side chain of tryptophan in peptides and proteins, it is important to have the appropriately protected homologs H‐β² HTrp OH and H‐β³ HTrp OH (Fig.) available for incorporation in β‐peptides. The β²‐HTrp building block is especially important, because β²‐amino acid residues cause β‐peptide chains to fold to the unusual 12/10 helix or to a hairpin turn. The preparation of Fmoc and Z β²‐HTrp(Boc) OH by Curtius degradation (Scheme 1) of a succinic acid derivative is described (Schemes 2–4). To this end, the (S)‐4‐isopropyl‐3‐[(N‐Boc‐indol‐3‐yl)propionyl]‐1,3‐oxazolidin‐2‐one enolate is alkylated with Br CH₂CO₂Bn (Scheme 3). Subsequent hydrogenolysis, Curtius degradation, and removal of the Evans auxiliary group gives the desired derivatives of (R)‐H β²‐HTrp OH (Scheme 4). Since the (R)‐form of the auxiliary is also available, access to (S)‐β²‐HTrp‐containing β‐peptides is provided as well.     

Amberlyst‐15‐Catalyzed Novel Synthesis of Quinoline Derivatives in Ionic Liquid

In recent years, ionic liquids have attracted much attention as useful synthetic solvents. Compared with classical molecular solvents, the ionic liquids are environmentally benign reaction media. A variety of quinoline derivatives have been synthesized under ionic liquid conditions using Amberlyst‐15 as catalyst.     

Stereoselective Synthesis of 1,2,3‐Triazolooxazine and Fused 1,2,3‐Triazolo‐δ‐Lactone Derivatives

The stereoselective synthesis of 1,2,3‐triazolooxazine and fused 1,2,3‐triazolo‐δ‐lactone by applying chemoenzymatic methods is described. trans‐2‐Azidocyclohexanol was successfully resolved by Novozyme 435 with an ee value of 99%. Installation of the alkyne moiety on the enantiomerically enriched azidoalcohol by O‐alkylation, followed by intramolecular azide? alkyne [3+2] cycloaddition resulted in the desired 1,2,3‐triazolooxazine derivative. Enantiomerically pure azidocyclohexanol was also subjected to the Huisgen 1,3‐dipolar cycloaddition reaction with dimethylacetylene dicarboxylate, followed by intramolecular cyclization of the corresponding cycloadduct, to furnish a fused 1,2,3‐triazolo‐δ‐lactone.     

Synthesis of Some Novel 1,4‐Phenylene‐bis‐thiazolyl Derivatives and Their Anti‐hypertensive α‐blocking Activity Screening

A series of novel 1,4‐phenylene‐bis‐thiazolyl derivatives were synthesized and evaluated for their anti‐hypertensive activities as α‐blocking agents and some of them showed promising activities.     

Synthesis of New Fused Thienopyrimidines Derivatives as Anti‐inflammatory Agents

5‐Amino‐2‐(p‐tolylamino)‐4‐phenylthieno[2,3‐d]pyrimidine‐6‐carbonitrile 9 , which was synthesized by an innovative method, was used as a versatile precursor for synthesizing pyrimido‐thienopyrimidine, triazolopyrimidothienopyrimidine, and pyrimidothienotriazine compounds. Thus, reaction of aminothienopyrimidinecarbonitrile 9 with chloroacetylchloride in dioxane afforded the chloroacetylaminocarbonitrile derivative 10 , which underwent nucleophilic substitution reactions with various primary and secondary amines gave the corresponding N‐alkyl‐(aryl)amino acetamides 11a,b . On the other hand, the reaction of aminocarbonitrile 9 with triethyl orthoformate followed by cyclization with hydrazine yielded an aminoiminopyrimidine derivative 13 . The latter was used as versatile precursor for synthesis of new heterocyclic compounds. The structures of all the new compounds have been established on the basis of their analytical and spectral data (IR, ¹H NMR, ¹³C NMR, and MS). Some of the synthesized compounds were evaluated in vitro for their anti‐inflammatory activity. All the tested compounds exhibited remarkable anti‐inflammatory activity.     

Studies on Synthesis of Novel Triazole Tagged Pyrazole Fused Naphthalene 5‐Thiazine‐5,5‐dioxide Derivatives,Their Antimicrobial,and Antioxidant Activity

A series of novel triazole tagged pyrazole fused naphthalene‐5‐thiazine‐5,5‐dioxide derivatives 8 and 9 were synthesized starting from sodium salt of saccharin 1 . The structure of each intermediate and products was established on the basis of spectroscopy data. All the synthesized compounds 8 and 9 were screened against various bacterial and fungal strains but found to show no activity up to 150‐µg/mL concentration. Further screening for antioxidant property resulted promising compounds.     

Synthesis of Novel 1,2,4‐oxadiazoline Derivatives Containing Quinoline Moiety by 1,3‐Dipolar Cycloaddition

A series of novel 1,2,4‐oxadiazoline derivatives containing 2‐(1,2,4‐triazol‐1‐yl)quinoline were synthesized by the reaction of imines with benzohydroximinoyl chlorides in the presence of Et₃N via 1,3‐diplolar cycloaddition reaction. The structures of the target compounds were confirmed by IR, ¹H NMR, MS, elemental, and X‐ray crystallographic analysis.     

The Efficient Synthesis of the Optically Active β‐Hydroxyl‐γ‐Butyrolactone Derivatives

The optically active β‐hydroxyl‐γ‐butyrolactones were synthesized from nonchiral starting material by employing reductive cleavage reaction, sharpless asymmetric epoxidation and dihydroxylation, and Lewis acid‐catalysed cyclization as key steps. This strategy can be used to prepare many chiral β‐hydroxyl‐γ‐butyrolactone analogues.     

Synthesis of β‐Substituted γ‐Aminobutyric Acid Derivatives through Enantioselective Photoredox Catalysis

β‐Substituted chiral γ‐aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β‐substituted γ‐aminobutyric acid derivatives through visible‐light‐induced photocatalyst‐free asymmetric radical conjugate additions is reported. Various β‐substituted γ‐aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42–89 %) and with excellent enantioselectivity (90–97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)‐pregabalin, (R)‐baclofen, (R)‐rolipram, and (S)‐nebracetam.