Benzhydrylquinazolinediones: Novel cytosolic phospholipase A2α inhibitors with improved physicochemical properties

Synthesis of 3-(Pyridin-2-yl)quinazolin-2,4(1H,3H)-diones via Annulation of Anthranilic Esters with N-pyridyl Ureas

A new route for the synthesis of quinazolin-2,4(1H,3H)-diones and thieno [2,3-d]pyrimidine-2,4(1H,3H)-diones substituted by pyridyl/quinolinyl moiety in position 3 has been developed. The proposed method concluded in an annulation of substituted anthranilic esters or 2-aminothiophene-3-carboxylates with 1,1-dimethyl-3-(pyridin-2-yl) ureas. The process consists of the formation of N-aryl-N'-pyridyl ureas followed by their cyclocondensation into the corresponding fused heterocycles. The reaction does not require the use of metal catalysts and proceeds with moderate to good yields (up to 89%). The scope of the method is more than 30 examples, including compounds with both electron-withdrawing and electron-donating groups, as well as diverse functionalities. At the same time, strong electron-acceptor substituents in the pyridine ring of the starting ureas reduce the product yield or even prevent the cyclocondensation step. The reaction can be easily scaled to gram quantities.

Synthesis and Biological Evaluation of Octahydroquinazolinones as Phospholipase A2, and Protease Inhibitors: Experimental and Theoretical Exploration

Phospholipase A2 (PLA2) promotes inflammation via lipid mediators and releases arachidonic acid (AA), and these enzymes have been found to be elevated in a variety of diseases, including rheumatoid arthritis, sepsis, and atherosclerosis. The mobilization of AA by PLA2 and subsequent synthesis of prostaglandins are regarded as critical events in inflammation. Inflammatory processes may be treated with drugs that inhibit PLA2, thereby blocking the COX and LOX pathways in the AA cascade. To address this issue, we report herein an efficient method for the synthesis of a series of octahydroquinazolinone compounds (4a-h) in the presence of the catalyst Pd-HPW/SiO₂ and their phospholipase A2, as well as protease inhibitory activities. Among eight compounds, two of them exhibited overwhelming results against PLA2 and protease. By using FT-IR, Raman, NMR, and mass spectroscopy, two novel compounds were thoroughly studied. After carefully examining the SAR of the investigated compounds against these enzymes, it was found that compounds (4a, 4b) containing both electron-donating and electron-withdrawing groups on the phenyl ring exhibited higher activity than compounds with only one of these groups. DFT studies were employed to study the electronic nature and reactivity properties of the molecules by optimizing at the BLYP/cc-pVDZ. Natural bond orbitals helped to study the various electron delocalizations in the molecules, and the frontier molecular orbitals helped with the reactivity and stability parameters. The nature and extent of the expressed biological activity of the molecule were studied using molecular docking with human non-pancreatic secretory phospholipase A2 (hnps-PLA2) (PDB ID: 1DB4) and protease K (PDB ID: 2PWB). The drug-ability of the molecule has been tested using ADMET, and pharmacodynamics data have been extracted. Both the compounds qualify for ADME properties and follow Lipinski's rule of five.

NiH-Catalyzed Proximal-Selective Hydroamination of Unactivated Alkenes with Anthranils

The regioselective hydroamination of unactivated alkenes is a long-standing challenge in organic synthesis. Herein, we report a NiH-catalyzed proximal-selective hydroamination of unactivated alkenes with 8-aminoquinoline (AQ) as a bidentate auxiliary and anthranils as aminating reagents. A wide range of primary aryl amines bearing an ortho-carbonyl group were installed in both terminal and internal unactivated alkenes, delivering a variety of valuable β- and γ-amino acid building blocks, respectively, with excellent regiocontrol. The utility of this transformation was further demonstrated by the conversion of the multifunctionalized aryl amines into useful N-heterocycles.

Nickel-Catalyzed Hydroamination of Olefins with Anthranils

A nickel-catalyzed polarity-reversed hydroamination of olefins has been achieved with anthranils as the electrophilic aminating agents and hydrosilane as the reductant. This protocol provides a facile access to N-alkyl-2-aminobenzophenones that are versatile intermediates in organic synthesis. A wide range of olefins and anthranils are compatible in this transformation, delivering the desired amines in useful to excellent yields (38 examples, up to 92% yield). The utility of this protocol is exhibited in the late-stage functionalization of drug molecules and the valuable derivatives of the obtained amination products.

2-Oxoamide inhibitors of cytosolic group IVA phospholipase A2 with reduced lipophilicity

Cytosolic GIVA phospholipase A2 (GIVA cPLA2) initiates the eicosanoid pathway of inflammation and thus inhibitors of this enzyme constitute novel potential agents for the treatment of inflammatory diseases. Traditionally, GIVA cPLA2 inhibitors have suffered systemically from high lipophilicity. We have developed a variety of long chain 2-oxoamides as inhibitors of GIVA PLA2. Among them, AX048 was found to produce a potent analgesic effect. We have now reduced the lipophilicity of AX048 by replacing the long aliphatic chain with a chain containing an ether linked aromatic ring with in vitro inhibitory activities similar to AX048.

N1,N3-disubstituted uracils as nonnucleoside inhibitors of HIV-1 reverse transcriptase

A series of phenyloxyethyl and cinnamyl derivatives of substituted uracils were synthesized and found to exhibit potent activity against HIV-RT and HIV replication in cell culture. In general, the cinnamyl derivatives proved superior to the phenyloxyethyl derivatives, however 1-[2-(4-methylphenoxy)ethyl]-3-(3,5-dimethylbenzyl)uracil (19) exhibited the highest activity (EC(50)=0.27 μM) thus confirming that the 3-benzyluracil fragment in the NNRTI structure can be regarded as a functional analogue of the benzophenone pharmacophore typically found in NNRTIs.

Inhibitors of Cytosolic Phospholipase A2α as Anti-inflammatory Drugs

Arachidonic acid derivatives, like prostaglandins and leukotrienes, as well as the alkyl-ether phospholipid platelet-activating factor (PAF) are highly active substances with diverse biological actions. Elevated levels of these lipid mediators in response to a variety of stimuli have been implicated in the pathology of many inflammatory diseases. The rate-limiting step in the generation of prostaglandins, leukotrienes and PAF, respectively, is the cleavage of the sn-2-ester of membrane phospholipids by a phospholipase A2 (PLA2). Among the superfamily of PLA2 enzymes, cytosolic PLA2α (cPLA2α, also referred to as group IVA PLA2) is thought to play the primary role in this biochemical reaction. Therefore, inhibition of cPLA2α activity is an attractive approach to the control of inflammatory disorders.

In this chapter the main groups of cPLA2α inhibitors are described and the problems associated with the development of clinical active drug candidates are discussed. Furthermore, in-vivo data obtained with such compounds in pre-clinical animal models of inflammation will be presented.

Total synthesis of a marine alkaloid--rigidin E

In the present paper, we report an efficient total synthesis of a marine alkaloid, rigidin E. The key tetrasubstituted 2-amino-3-carboxamidepyrrole intermediate was synthesized by cascade Michael addition/intramolecular cyclization between N-(2-(4-(benzyloxy)phenyl)-2-oxoethyl)methanesulfonamide and 3-(4-(benzyloxy)phenyl)-2-cyano-N-methylacrylamide. Subsequent carbonylation with triphosgene catalyzed by I(2) and deprotection of benzyl groups afforded rigidin E in 21% overall yield. This strategy has the merits of metal-free reactions, low cost, mild reaction protocols, and easy access to diversity-oriented derivatives for potential structure-activity relationship investigation.

Design of novel and potent cPLA2α inhibitors containing an α-methyl-2-ketothiazole as a metabolically stable serine trap

We report the design of novel, potent cPLA(2)α inhibitors that possess an α-methyl-2-ketothiazole that acts as a serine-reactive moiety. We describe the optimization of the series for potency and metabolic stability towards ketone reduction. This was achieved by attenuating the reactivity of the ketone using a combination of electronic and steric effects.