Preparation,Crystal Structure and Explosive Properties of Copper(II) Perchlorate Complex with 4‐Amino‐1,2,4‐Triazole and Water

A complex from copper(II) perchlorate with 4‐amino‐1,2,4‐triazole (4‐AT, C₂H₄N₄) was synthesized, and elemental composition, molecular structure, and explosive properties were determined. To this end, elemental and X‐ray analyses were carried out, sensitivity to mechanical and thermal stimuli was measured, mechanism of thermal decomposition was investigated, and kinetic parameters of decomposition were determined. In the next step measurements of heat of combustion and detonation velocity were performed. Detonation parameters were also calculated. It was stated that the complex has slightly distorted square bipyramidal (4+2) coordination. The four basal bonds are formed by nitrogen atoms of four 4‐AT molecules. The coordination of the metal is completed by two axial oxygen atoms, one of the perchlorate ion, and one of the water molecule. With respect to explosive properties, tetrakis(4‐AT)copper(II) perchlorate monohydrate belongs to the group of sensitive secondary explosives.     

Atomic‐Resolution Structure of a Class C β‐Lactamase and Its Complex with Avibactam

β‐Lactamases (BLs) are important antibiotic‐resistance determinants that significantly compromise the efficacy of valuable β‐lactam antibacterial drugs. Thus, combinations with BL inhibitor were developed. Avibactam is the first non‐β‐lactam BL inhibitor introduced into clinical practice. Ceftazidime–avibactam represents one of the few last‐resort antibiotics available for the treatment of infections caused by near‐pandrug‐resistant bacteria. TRU‐1 is a chromosomally encoded AmpC‐type BL of Aeromonas enteropelogenes, related to the FOX‐type BLs and constitutes a good model for class C BLs. TRU‐1 crystals provided ultrahigh‐resolution diffraction data for the native enzyme and for its complex with avibactam. A comparison of the native and avibactam‐bound structures revealed new details in the conformations of residues relevant for substrate and/or inhibitor binding. Furthermore, a comparison of the TRU‐1 and Pseudomonas aeruginosa AmpC avibactam‐bound structures revealed two inhibitor conformations that were likely to correspond to two different states occurring during inhibitor carbamylation/recyclization.     

Phage Display to Identify Nedd8‐Mimicking Peptides as Inhibitors of the Nedd8 Transfer Cascade

The Nedd8 activating enzyme (NAE) launches the transfer of the ubiquitin‐like protein Nedd8 through an enzymatic cascade to covalently modify a diverse array of proteins, thus regulating their biological functions in the cell. The C‐terminal peptide of Nedd8 extends deeply into the active site of NAE and plays an important role in the specific recognition of Nedd8 by NAE. We used phage display to profile C‐terminal mutant sequences of Nedd8 that could be recognized by NAE for the activation reaction. We found that NAE can accommodate diverse changes in the Nedd8 C‐terminal sequence (⁷¹LALRGG⁷⁶), including Arg and Ile replacing Leu71, Leu, Ser, and Gln replacing Ala72, and substitutions by bulky aromatic residues at positions 73 and 74. We also observed that short peptides corresponding to the C‐terminal sequences of the Nedd8 variants can be activated by NAE to form peptide～NAE thioester conjugates. Once NAE is covalently loaded with these Nedd8‐mimicking peptides, it can no longer activate full‐length Nedd8 for transfer to the neddylation targets, such as the cullin subunits of cullin‐RING E3 ubiquitin ligases (CRLs). We have thus developed a new method to inhibit protein neddylation by Nedd8‐mimicking peptides.     

Fluorophore‐Labeled Cyclooxygenase‐2 Inhibitors for the Imaging of Cyclooxygenase‐2 Overexpression in Cancer: Synthesis and Biological Studies

A group of cyclooxygenase‐2 (COX‐2)‐specific fluorescent cancer biomarkers were synthesized by linking the anti‐inflammatory drugs ibuprofen, (S)‐naproxen, and celecoxib to the 7‐nitrobenzofurazan (NBD) fluorophore. In vitro COX‐1/COX‐2 inhibition studies indicated that all of these fluorescent conjugates are COX‐2 inhibitors (IC₅₀ range: 0.19–23.0 μM ) with an appreciable COX‐2 selectivity index (SI≥4.3–444). In this study the celecoxib–NBD conjugate N‐(2‐((7‐nitrobenzo[c][1,2,5]oxadiazol‐4‐yl)amino)ethyl)‐4‐(5‐(p‐tolyl)‐3‐(trifluoromethyl)‐1H‐pyrazol‐1‐yl)benzenesulfonamide ( 14 ), which displayed the highest COX‐2 inhibitory potency and selectivity (COX‐2 IC₅₀=0.19 μM ; SI=443.6), was identified as an impending COX‐2‐specific biomarker for the fluorescence imaging of cancer using a COX‐2‐expressing human colon cancer cell line (HCA‐7).     

Design,Synthesis, and Evaluation of 2‐Amino‐6‐nitrobenzothiazole‐Derived Hydrazones as MAO Inhibitors: Role of the Methylene Spacer Group

A series of 2‐amino‐6‐nitrobenzothiazole‐derived extended hydrazones were designed, synthesized, and investigated for their ability to inhibit monoamine oxidase A and B (MAO‐A/MAO‐B). The compounds were found to exhibit inhibitory activities in the nanomolar to micromolar range. Some of the compounds showed excellent potency and selectivity against the MAO‐B isoform. N′‐(5‐Chloro‐2‐oxoindolin‐3‐ylidene)‐2‐(6‐nitrobenzothiazol‐2‐ylamino)acetohydrazide (compound 31 ) showed the highest MAO‐B inhibitory activity (IC₅₀=1.8±0.3 nm , selectivity index [SI]=766.67), whereas compound 6 [N′‐(1‐(4‐bromophenyl)ethylidene)‐2‐(6‐nitrobenzothiazol‐2‐ylamino)acetohydrazide] was found to be the most active MAO‐A inhibitor (IC₅₀=0.42±0.003 μm ). Kinetic studies revealed that compounds 6 and 31 exhibit competitive‐type reversible inhibition against both MAO‐A and MAO‐B, respectively. Structure–activity relationship (SAR) studies disclosed several structural aspects significant for potency and the contribution of the methylene spacer toward MAO‐B inhibitory potency, with minimal or no neurotoxicity. Molecular modeling studies yielded a good correlation between experimental and theoretical inhibitory data. Binding pose analysis revealed the significance of cumulative effects of π–π stacking and hydrogen bond interactions for effective stabilization of virtual ligand–protein complexes. Further optimization studies of compound 31 , including co‐crystallization of inhibitor–MAO‐B complexes, are essential to develop these compounds as potential therapeutic agents for MAO‐B‐associated neurodegenerative diseases.     

6‐Amino‐6‐deoxy‐5,6‐di‐N‐(N′‐octyliminomethylidene)nojirimycin: Synthesis,Biological Evaluation,and Crystal Structure in Complex with Acid β‐Glucosidase

6‐Amino‐6‐deoxy‐5,6‐di‐ N ‐( N ′‐octyliminomethylidene)nojirimycin , a reducing analogue of N‐nonyl‐1‐deoxynojirimycin, proved to be a potent and very selective inhibitor of β‐glucosidases, including human acid β‐glucosidase. Structural studies of the enzyme–inhibitor complex showed a binding mode in which the anomeric hydroxy group is accommodated in the “wrong” α configuration.

     

4‐Biphenylalanine‐ and 3‐Phenyltyrosine‐Derived Hydroxamic Acids as Inhibitors of the JumonjiC‐Domain‐Containing Histone Demethylase KDM4A

Overexpression of the histone lysine demethylase KDM4A, which regulates H3K9 and H3K36 methylation states, has been related to the pathology of several human cancers. We found that a previously reported hydroxamate‐based histone deacetylase (HDAC) inhibitor (SW55) was also able to weakly inhibit this demethylase with an IC₅₀ value of 25.4 μm . Herein we report the synthesis and biochemical evaluations, with two orthogonal in vitro assays, of a series of derivatives of this lead structure. With extensive chemical modifications on the lead structure, also by exploiting the versatility of the radical arylation with aryldiazonium salts, we were able to increase the potency of the derivatives against KDM4A to the low‐micromolar range and, more importantly, to obtain demethylase selectivity with respect to HDACs. Cell‐permeable derivatives clearly showed a demethylase‐inhibition‐dependent antiproliferative effect against HL‐60 human promyelocytic leukemia cells.     

Probing the Peptidylglycine α‐Hydroxylating Monooxygenase Active Site with Novel 4‐Phenyl‐3‐butenoic Acid Based Inhibitors

Specific inhibition of the copper‐containing peptidylglycine α‐hydroxylating monooxygenase (PHM), which catalyzes the post‐translational modification of peptides involved in carcinogenesis and tumor progression, constitutes a new approach for combating cancer. We carried out a structure–activity study of new compounds derived from a well‐known PHM substrate analogue, the olefinic compound 4‐phenyl‐3‐butenoic acid (PBA). We designed, synthesized, and tested various PBA derivatives both in vitro and in silico. We show that it is possible to increase PBA affinity for PHM by appropriate functionalization of its aromatic nucleus. Compound 2 d , for example, bears a meta‐benzyloxy substituent, and exhibits better inhibition features (K_i=3.9 μM , k_inact/K_i=427 M ^?1 s^?1) than the parent PBA (K_i=19 μM , k_inact/K_i=82 M ^?1 s^?1). Docking calculations also suggest two different binding modes for PBA derivatives; these results will aid in the development of further PHM inhibitors with improved features.     

Synthesis and Structure–Activity Relationship Studies of Derivatives of the Dual Aromatase–Sulfatase Inhibitor 4‐{[(4‐Cyanophenyl)(4H‐1,2,4‐triazol‐4‐yl)amino]methyl}phenyl sulfamate

4‐{[(4‐Cyanophenyl)(4H‐1,2,4‐triazol‐4‐yl)amino]methyl}phenyl sulfamate and its ortho‐halogenated (F, Cl, Br) derivatives are first‐generation dual aromatase and sulfatase inhibitors (DASIs). Structure–activity relationship studies were performed on these compounds, and various modifications were made to their structures involving relocation of the halogen atom, introduction of more halogen atoms, replacement of the halogen with another group, replacement of the methylene linker with a difluoromethylene linker, replacement of the para‐cyanophenyl ring with other ring structures, and replacement of the triazolyl group with an imidazolyl group. The most potent in vitro DASI discovered is an imidazole derivative with IC₅₀ values against aromatase and steroid sulfatase in a JEG‐3 cell preparation of 0.2 and 2.5 nM , respectively. The parent phenol of this compound inhibits aromatase with an IC₅₀ value of 0.028 nM in the same assay.     

Aluminium(III) Chloride‐Catalyzed Three‐Component Condensation of Aromatic Aldehydes,Nitroalkanes and Sodium Azide for the Synthesis of 4‐Aryl‐NH‐1,2,3‐triazoles

An aluminium(III) chloride‐catalyzed three‐component reaction of aromatic aldehydes, nitroalkanes, and sodium azide has been developed; this reaction sequence can be applied to a broad substrate scope and affords the corresponding 4‐aryl‐NH‐1,2,3‐triazoles in good to excellent yields. The milder reaction conditions and easier operation make this AlCl₃‐catalyzed protocol more advantageous for the synthesis of 4‐aryl‐NH‐1,2,3‐triazoles.

     

Bicyclic Derivatives of the Potent Dual Aromatase–Steroid Sulfatase Inhibitor 2‐Bromo‐4‐{[(4‐cyanophenyl)(4H‐1,2,4‐triazol‐4‐yl)amino]methyl}phenylsulfamate: Synthesis,SAR, Crystal Structure,and in vitro and in vivo Activities

The design and synthesis of a series of bicyclic ring containing dual aromatase–sulfatase inhibitors (DASIs) based on the aromatase inhibitor (AI) 4‐[(4‐bromobenzyl)(4H‐1,2,4‐triazol‐4‐yl)amino]benzonitrile are reported. Biological evaluation with JEG‐3 cells revealed structure–activity relationships. The X‐ray crystal structure of sulfamate 23 was determined, and selected compounds were docked into the aromatase and steroid sulfatase (STS) crystal structures. In the sulfamate‐containing series, compounds containing a naphthalene ring are both the most potent AI ( 39 , IC_{50 AROM}=0.25 nM ) and the best STS inhibitor ( 31 , IC_{50 STS}=26 nM ). The most promising DASI is 39 (IC_{50 AROM}=0.25 nM , IC_{50 STS}=205 nM ), and this was evaluated orally in vivo at 10 mg kg^?1, showing potent inhibition of aromatase (93 %) and STS (93 %) after 3 h. Potent aromatase and STS inhibition can thus be achieved with a DASI containing a bicyclic ring system; development of such a DASI could provide an attractive new option for the treatment of hormone‐dependent breast cancer.     

Preparation the Key Intermediate of Angiotensin‐Converting Enzyme (ACE) Inhibitors: High Enantioselective Production of Ethyl (R)‐2‐Hydroxy‐4‐Phenylbutyrate with Candida boidinii CIOC21

Forty microorganisms belonging to different taxonomical groups were used to catalyze the enantioselective reduction of ethyl 2‐oxophenylbutyrate to afford the corresponding ethyl 2‐hydroxy‐4‐phenylbutyrate. Several microorganisms led to over 99% ee of ethyl (S)‐2‐hydroxy‐4‐phenylbutyrate. Especially, we firstly found that the Candida boidinii CIOC21 could be effectively used for the enantioselective preparation the ethyl (R)‐2‐hydroxy‐4‐phenylbutyrate in pure aqueous medium with 99% ee, a key intermediate in the production of angiotensin‐converting enzyme (ACE) inhibitors.     

Evaluation of (4‐Arylpiperidin‐1‐yl)cyclopentanecarboxamides As High‐Affinity and Long‐Residence‐Time Antagonists for the CCR2 Receptor

Animal models suggest that the chemokine ligand 2/CC‐chemokine receptor 2 (CCL2/CCR2) axis plays an important role in the development of inflammatory diseases. However, CCR2 antagonists have failed in clinical trials because of a lack of efficacy. We previously described a new approach for the design of CCR2 antagonists by the use of structure–kinetics relationships (SKRs). Herein we report new findings on the structure–affinity relationships (SARs) and SKRs of the reference compound MK‐0483, its diastereomers, and its structural analogues as CCR2 antagonists. The SARs of the 4‐arylpiperidine group suggest that lipophilic hydrogen‐bond‐accepting substituents at the 3‐position are favorable. However, the SKRs suggest that a lipophilic group with a certain size is desired [e.g., 3‐Br: K_i=2.8 nM , residence time (t_res)=243 min; 3‐iPr: K_i=3.6 nM , t_res=266 min]. Alternatively, additional substituents and further optimization of the molecule, while keeping a carboxylic acid at the 3‐position, can also prolong t_res; this was most prominently observed in MK‐0483 (K_i=1.2 nM , t_res=724 min) and a close analogue (K_i=7.8 nM ) with a short residence time.     

Expanding the Binding Envelope of CYP51 Inhibitors Targeting Trypanosoma cruzi with 4‐Aminopyridyl‐Based Sulfonamide Derivatives

Chagas disease is a chronic infection caused by the protozoan parasite Trypanosoma cruzi, manifested in progressive cardiomyopathy and/or gastrointestinal dysfunction. Therapeutic options to prevent or treat Chagas disease are limited. CYP51, the enzyme key to the biosynthesis of eukaryotic membrane sterols, is a validated drug target in both fungi and T. cruzi. Sulfonamide derivatives of 4‐aminopyridyl‐based inhibitors of T. cruzi CYP51 (TcCYP51), including the sub‐nanomolar compound 3 , have molecular structures distinct from other validated CYP51 inhibitors. They augment the biologically relevant chemical space of molecules targeting TcCYP51. In a 2.08 Å X‐ray structure, TcCYP51 is in a conformation that has been influenced by compound 3 and is distinct from the previously characterized ground‐state conformation of CYP51 drug–target complexes. That the binding site was modulated in response to an incoming inhibitor for the first time characterizes TcCYP51 as a flexible target rather than a rigid template.     

Synthesis and in vitro Evaluation of West Nile Virus Protease Inhibitors Based on the 2‐{6‐[2‐(5‐Phenyl‐4H‐{1,2,4]triazol‐3‐ylsulfanyl)acetylamino]benzothiazol‐2‐ylsulfanyl}acetamide Scaffold

In recent years, clinical symptoms resulting from West Nile virus (WNV) infection have worsened in severity, with an increased frequency in neuroinvasive diseases among the elderly. As there are presently no successful therapies against WNV for use in humans, continual efforts to develop new chemotherapeutics against this virus are highly desired. The viral NS2B‐NS3 protease is a promising target for viral inhibition due to its importance in viral replication and its unique substrate preference. In this study, a WNV NS2B‐NS3 protease inhibitor with a 2‐{6‐[2‐(5‐phenyl‐4H‐[1,2,4]triazol‐3‐ylsulfanyl)acetylamino]benzothiazol‐2‐ylsulfanyl}acetamide scaffold was identified during screening. Optimization of this initial hit by synthesis and screening of a focused compound library with this scaffold led to the identification of a novel uncompetitive inhibitor ( 1 a24 , IC₅₀=3.4±0.2 μM ) of the WNV NS2B‐NS3 protease. Molecular docking of 1 a24 into the WNV protease showed that the compound interferes with productive interactions of the NS2B cofactor with the NS3 protease and is an allosteric inhibitor of the WNV NS3 protease.     

Synthesis and Biological Evaluation of 4‐Sulfamoylphenyl/Sulfocoumarin Carboxamides as Selective Inhibitors of Carbonic Anhydrase Isoforms hCA II,IX, and XII

With the aim to develop potent and selective human carbonic anhydrase inhibitors (hCAIs), we synthesized 4‐sulfamoylphenyl/sulfocoumarin benzamides (series 5 a – r and series 7 a – q ) and evaluated their inhibition profiles against five isoforms of the zinc‐containing human carbonic anhydrase (hCA, EC 4.2.1.1): cytosolic hCA I and II, and the transmembrane isozymes hCA IV, IX, and XII. Compounds 5 a – r were found to selectively inhibit hCA II in the nanomolar range, while being less effective against the other hCA isoforms. As noted from the literature, sulfocoumarin (1,2‐benzoxathiine 2,2‐dioxide) acts as a “prodrug” inhibitor and is hydrolyzed by the esterase activity of hCA to form 2‐hydroxyphenylvinylsulfonic acid, which thereafter binds to the enzyme in a manner similar to that of coumarins and sulfoxocoumarins. All these sulfocoumarins (compounds 7 a – q ) were found to be very weak or ineffective as inhibitors of the housekeeping off‐target hCA isoforms I and II, and effectively inhibited the transmembrane tumor‐associated isoforms IX and XII in the high nanomolar to micromolar ranges. Further structural modifications of these molecules could be useful for the development of effective hCA inhibitors used for the treatment of glaucoma, epilepsy, and cancer.     

Linear and Cyclic Depsipeptidomimetics with β‐Lactam Cores: A Class of New αvβ3 Integrin Receptor Inhibitors

The α_vβ₃ integrin receptor plays an important role in tumor metastasis and tumor‐induced angiogenesis. The inhibition of this receptor with diverse ligands, antibodies, or cyclic peptides is a promising research field for the treatment of a variety of tumors. The replacement of Phe‐(Me)Val dipeptide by a β‐lactam ring in Cilengitide has led to new products that show higher inhibitory activity than the parent cyclopeptide. In particular, substitution of a peptide bond β‐lactam‐NH‐Asp linkage by a β‐lactam‐O‐Asp ester linkage increases the activity of the new cyclodepsipeptide. In the same way it has been found that open‐chain compounds of the form Asp‐β‐lactam‐Arg can interact with the receptor and inhibit its activity moderately. The integrin inhibitory activity of the synthesized compounds has been established by using the CGH array, a method that appears to be a more reliable trial than the classical adhesion test.