5-((3-Amidobenzyl)oxy)nicotinamides as SIRT2 Inhibitors: A Study of Constrained Analogs.

SIRT2 is a member of NAD-dependent sirtuins and its inhibition has been proposed as a promising therapeutic approach for treating human diseases, including neurodegenerative diseases, cancer, and infections. Expanding SIRT2 inhibitors based on the 3-aminobenzyloxy nicotinamide core structure, we have synthesized and evaluated constrained analogs and selected stereoisomers. Our structure-activity relationship (SAR) study has revealed that 2,3-constrained ()-isomers possess enhanced in vitro enzymatic inhibitory activity against SIRT2 and retain excellent selectivity over SIRT1 and SIRT3, provided that a suitable ring A is used.

UNC-45A Is a Novel Microtubule-Associated Protein and Regulator of Paclitaxel Sensitivity in Ovarian Cancer Cells.

UNC-45A, a highly conserved member of the UCS (UNC45A/CRO1/SHE4P) protein family of cochaperones, plays an important role in regulating cytoskeletal-associated functions in invertebrates and mammalian cells, including cytokinesis, exocytosis, cell motility, and neuronal development. Here, for the first time, UNC-45A is demonstrated to function as a mitotic spindle-associated protein that destabilizes microtubules (MT) activity. Using biophysical reconstitution and total internal reflection fluorescence microscopy analysis, we reveal that UNC-45A directly binds to taxol-stabilized MTs in the absence of any additional cellular cofactors or other MT-associated proteins and acts as an ATP-independent MT destabilizer.

-(1-Benzyl-3,5-dimethyl-1-pyrazol-4-yl)benzamides: Antiproliferative Activity and Effects on mTORC1 and Autophagy.

Guided by antiproliferative activity in MIA PaCa-2 cells, we have performed preliminary structure-activity relationship studies on -(1-benzyl-3,5-dimethyl-1-pyrazol-4-yl)benzamides. Two selected compounds showed submicromolar antiproliferative activity and good metabolic stability. Both compounds reduced mTORC1 activity and increased autophagy at the basal level.

5-((3-Amidobenzyl)oxy)nicotinamides as Sirtuin 2 Inhibitors.

Derived from our previously reported human sirtuin 2 (SIRT2) inhibitors that were based on a 5-aminonaphthalen-1-yloxy nicotinamide core structure, 5-((3-amidobenzyl)oxy)nicotinamides offered excellent activity against SIRT2 and high isozyme selectivity over SIRT1 and SIRT3. Selected compounds also exhibited generally favorable in vitro absorption, distribution, metabolism, and excretion properties. Kinetic studies revealed that a representative SIRT2 inhibitor acted competitively against both NAD(+) and the peptide substrate, an inhibitory modality that was supported by our computational study.

mTORC1 Coordinates Protein Synthesis and Immunoproteasome Formation via PRAS40 to Prevent Accumulation of Protein Stress.

Reduction of translational fidelity often occurs in cells with high rates of protein synthesis, generating defective ribosomal products. If not removed, such aberrant proteins can be a major source of cellular stress causing human diseases. Here, we demonstrate that mTORC1 promotes the formation of immunoproteasomes for efficient turnover of defective proteins and cell survival.

Design and synthesis of an activity-based protein profiling probe derived from cinnamic hydroxamic acid.

In our continued effort to discover new anti-hepatitis C virus (HCV) agents, we validated the anti-replicon activity of compound 1, a potent and selective anti-HCV hydroxamic acid recently reported by us. Generally favorable physicochemical and in vitro absorption, distribution, metabolism, and excretion (ADME) properties exhibited by 1 made it an ideal parent compound from which activity-based protein profiling (ABPP) probe 3 was designed and synthesized. Evaluation of probe 3 revealed that it possessed necessary anti-HCV activity and selectivity.

A Novel Sirtuin-3 Inhibitor, LC-0296, Inhibits Cell Survival and Proliferation, and Promotes Apoptosis of Head and Neck Cancer Cells.

Background: The survival rate of patients with head and neck squamous cell carcinoma (HNSCC) stands at approximately 50% and this has not improved in decades. This study developed a novel sirtuin-3 (SIRT3) inhibitor (LC-0296) and examined its role in altering HNSCC tumorigenesis.

Materials And Methods: The effect of the SIRT3 inhibitor, LC-0296, on cell survival, proliferation, and apoptosis, and reactive oxygen species levels in HNSCC cells were studied.

Hydroxamic acids block replication of hepatitis C virus.

Intrigued by the role of protein acetylation in hepatitis C virus (HCV) replication, we tested known histone deacetylase (HDAC) inhibitors and a focused library of structurally simple hydroxamic acids for inhibition of a HCV subgenomic replicon. While known HDAC inhibitors with varied inhibitory profiles proved to be either relatively toxic or ineffective, structure-activity relationship (SAR) studies on cinnamic hydroxamic acid and benzo[b]thiophen-2-hydroxamic acid gave rise to compounds 22 and 53, which showed potent and selective anti-HCV activity and therefore are promising starting points for further structural optimization and mechanistic studies.

Discovery of potent and selective sirtuin 2 (SIRT2) inhibitors using a fragment-based approach.

Sirtuin 2 (SIRT2) is one of the sirtuins, a family of NAD(+)-dependent deacetylases that act on a variety of histone and non-histone substrates. Accumulating biological functions and potential therapeutic applications have drawn interest in the discovery and development of SIRT2 inhibitors. Herein we report our discovery of novel SIRT2 inhibitors using a fragment-based approach.

Asymmetric synthesis of α-amino-1,3-dithianes via chiral N-phosphonyl imine-based Umpolung reaction without using chromatography and recrystallization.

A series of α-amino-1,3-dithianes have been synthesized via the asymmetric Umpolung reaction of 2-lithio-1,3-dithianes with chiral N-phosphonyl imines in good chemical yields (up to 82%) and good to excellent diastereoselectivities (>99:1). The manner by which chiral N-phosphonyl imines are slowly added into the solution of 2-lithio-1,3-dithiane was found to be crucial for achieving excellent diastereoselectivity. The current synthesis was proven to follow the GAP chemistry (group-assistant-purification chemistry) process, which avoids traditional purification techniques of chromatography or recrystallization, i.

Microwave enabled umpulong mechanism based rapid and efficient four- and six-component domino formations of 2-(2'-azaaryl)imidazoles and anti-1,2-diarylethylbenzamides.

Concise and efficient six-component and four-component domino approaches to anti-1,2-diarylethylbenzamides and highly substituted 2-(2'-azaaryl)imidazoles have been developed under solvent-free and microwave-irradiation conditions. The reactions showed a broad scope of substrates in which a wide range of common commercial aromatic aldehydes and heteroaryl nitriles can be used. The syntheses were finished within short periods (15-34 min) with good to excellent chemical yields and stereoselectivity that avoided tedious workup isolations.

Chiral N-phosphonyl imine chemistry: asymmetric synthesis of alpha,beta-diamino esters by reacting phosphonyl imines with glycine enolates.

Chiral phosphonyl imines attached with N-isopropyl protection group were found to react with lithium glycine enolates under convenient conditions to give alpha,beta-diamino esters. Thirteen examples have been examined in good to excellent chemical yields (85-97%) diastereoselectivity (up to 99% de). By treating with HBr at room temperature, the chiral auxiliary can be readily removed and recycled.

Chiral N-phosphonyl imine chemistry: asymmetric synthesis of alpha-alkyl beta-amino ketones by reacting phosphonyl imines with ketone-derived enolates.

A series of new chiral syn-alpha-branched beta-amino ketones has been synthesized by reacting chiral phosphonyl imines with ketone-derived enolates. The N-protection group on imine auxiliary was found to be crucial to the asymmetric induction. The absolute stereochemistry has been unambiguously determined by converting a product to a known sample.

Chiral N-phosphonyl imine chemistry: asymmetric additions of ester enolates for the synthesis of beta-amino acids.

Chiral phosphonyl imines attached by 1-naphthyl protection group were found to react with lithium ester enolates smoothly and give chiral beta-amino esters in good yields (70-88%) and up to excellent diastereoselectivity (>99:1 dr). Triisopropoxytitanium (IV) chloride was found to enhance diastereoseletivity when used as the Lewis acid promoter. The chiral auxiliary can be readily removed by treating with HBr to give free amino esters.

Chiral N-phosphonyl imine chemistry: asymmetric aza-Henry reaction.

A series of chiral N-phosphonyl imines have been synthesized and utilized successfully in asymmetric aza-Henry reaction. The chiral auxiliary was optimized for this reaction by varying different R groups on the nitrogen atoms. The reaction is convenient to perform to give excellent yields and good diastereoselectivities.

Determination of the C4-H bond dissociation energies of NADH models and their radical cations in acetonitrile.

Heterolytic and homolytic bond dissociation energies of the C4-H bonds in ten NADH models (seven 1,4-dihydronicotinamide derivatives, two Hantzsch 1,4-dihydropyridine derivatives, and 9,10-dihydroacridine) and their radical cations in acetonitrile were evaluated by titration calorimetry and electrochemistry, according to the four thermodynamic cycles constructed from the reactions of the NADH models with N,N,N',N'-tetramethyl-p-phenylenediamine radical cation perchlorate in acetonitrile (note: C9-H bond rather than C4-H bond for 9,10-dihydroacridine; however, unless specified, the C9-H bond will be described as a C4-H bond for convenience). The results show that the energetic scales of the heterolytic and homolytic bond dissociation energies of the C4-H bonds cover ranges of 64.2-81.