An aldol-based ‘build/couple/pair’ (B/C/P) strategy was applied to generate a collection of stereochemically and skeletally diverse small molecules. In the build phase, a series of asymmetric syn- and anti- aldol reactions were performed to produce four stereoisomers of a Boc protected γ-amino acid. In addition both stereoisomers of O-PMB-protected alaninol were generated to provide a chiral amine coupling partner. In the couple step, eight stereoisomeric amides were synthesized by coupling the chiral acid and amine building blocks. The amides were subsequently reduced to generate the corresponding secondary amines. In the pair phase, three different reactions were employed to enable intramolecular ring-forming processes, namely: nucleophilic aromatic substitution (SNAr), Huisgen [3+2] cycloaddition and ring-closing metathesis (RCM). Despite some stereochemical dependencies, the ring-forming reactions were optimized to proceed with good to excellent yields providing a variety of skeletons ranging in size from 8- to 14-membered rings. Scaffolds resulting from the RCM pairing reaction were diversified on solid-phase to yield a 14,400-membered library of macrolactams. Screening of this library led to the discovery of a novel class of histone deacetylase inhibitors, which display mixed enzyme inhibition and led to increased levels of acetylation in a primary mouse neuron culture. The development of stereo-structure/activity relationships (SSAR) was made possible by screening all 16 stereoisomers of the macrolactams produced through the aldol-based B/C/P strategy.

Nuclear factor-erythroid 2 related factor 2 (Nrf2)-mediated signaling plays a central role in maintaining cellular redox homeostasis of hepatic cells. Carbon monoxide releasing molecule-A1 (CORM-A1) has been reported to stimulate up-regulation and nuclear translocation of Nrf2 in hepatocytes. However, the role of CORM-A1 in improving lipid metabolism, antioxidant signaling and mitochondrial functions in nonalcoholic steatohepatitis (NASH) is unknown. In this study, we report that CORM-A1 prevents hepatic steatosis in high fat high fructose (HFHF) diet fed C57BL/6J mice, used as model of NASH. The beneficial effects of CORM-A1 in HFHF fed mice was associated with improved lipid homeostasis, Nrf2 activation, upregulation of antioxidant responsive (ARE) genes and increased ATP production. As, mitochondria are intracellular source of reactive oxygen species (ROS) and important sites of lipid metabolism, we further investigated the mechanisms of action of CORM-A1-mediated improvement in mitochondrial function in palmitic acid (PA) treated HepG2 cells. Cellular oxidative stress and cell viability were found to be improved in PA + CORM-A1 treated cells via Nrf2 translocation and activation of cytoprotective genes. Furthermore, in PA treated cells, CORM-A1 improved mitochondrial oxidative stress, membrane potential and rescued mitochondrial biogenesis thru upregulation of Drp1, TFAM, PGC-1α and NRF-1 genes. CORM-A1 treatment improved cellular status by lowering glycolytic respiration and maximizing OCR. Improvement in mitochondrial respiration and increment in ATP production in PA + CORM-A1 treated cells further corroborate our findings. In summary, our data demonstrate for the first time that CORM-A1 ameliorates tissue damage in steatotic liver via Nrf2 activation and improved mitochondrial function, thus, suggesting the anti-NASH potential of CORM-A1.

The synthesis of a stereochemically diverse library of medium-sized rings accessible via a ‘build/couple/pair’ strategy is described. Key aspects of the synthesis include SNAr cycloetherification of a linear amine template to afford eight stereoisomeric 8-membered lactams and subsequent solid-phase diversification of these scaffolds to yield a 6488-membered library. Screening of this compound collection in a cell-based assay for the suppression of cytokine-induced beta-cell apoptosis resulted in the identification of a small-molecule suppressor capable of restoring glucose-stimulated insulin secretion in a rat beta-cell line. The presence of all stereoisomers in the screening collection enabled preliminary determination of the structural and stereochemical requirements for cellular activity, while efficient follow-up chemistry afforded BRD-0476 (probe ML187), which had an approximately three-fold increase in activity. These results demonstrate the utility of diversity-oriented synthesis to probe discovery using cell-based screening, and the importance of including stereochemical diversity in screening collections for the development of stereo/structure-activity relationships.

Synthesis of bacterial cell wall peptidoglycan requires glycosyltransferase enzymes that transfer the disaccharide-peptide from lipid II onto the growing glycan chain. The polymerization of the glycan chain precedes cross-linking by penicillin-binding proteins and is essential for growth for key bacterial pathogens. As such, bacterial cell wall glycosyltransferases are an attractive target for antibiotic drug discovery. However, significant challenges to the development of inhibitors for these targets include the development of suitable assays and chemical matter that is suited to the nature of the binding site. We developed glycosyltransferase enzymatic activity and binding assays using the natural products moenomycin and vancomycin as model inhibitors. In addition, we designed a library of disaccharide compounds based on the minimum moenomycin fragment with peptidoglycan glycosyltransferase inhibitory activity and based on a more drug-like and synthetically versatile disaccharide building block. A subset of these disaccharide compounds bound and inhibited the glycosyltransferase enzymes, and these compounds could serve as chemical entry points for antibiotic development.

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A diversity-oriented synthesis (DOS) strategy was developed for the synthesis of stereochemically diverse fused-ring systems containing a pyran moiety. Each scaffold contains an amine and methyl ester for future diversification via amine capping and amide coupling. Scaffold diversity was evaluated in comparison to previously prepared scaffolds via a shape-based principal moments of inertia (PMI) analysis.

All stereoisomers of a highly functionalized 2,3-unsaturated C-glycoside can be accessed in 10-100 g quantities from readily available starting materials and reagents in 3-7 steps. These chiral scaffolds contain three stereogenic centers along with orthogonally protected functional groups for downstream reactivity.Due to their synthetic versatility and high level of stereochemical diversity carbohydrates have served as useful starting points for generating molecular diversity. 1 Carbohydratederived glycals in particular have been employed in multiple diversity-oriented synthesis (DOS) pathways. 2 Of interest to us was the utility of C-alkyl pseudoglycals for developing new build/couple/pair pathways in the context of library development. 3 In the present study, we focused on the synthesis of 2,3-unsaturated C-glycosides 1-4 ( Figure 1) which incorporate four chemical handles: (1) an ester, (2) an alkene, (3) a primary alcohol and (4) a secondary alcohol/primary amine, thereby, providing a range of options for subsequent modifications and/or functional group pairing reactions. 4 As part of our design strategy we sought to develop methods for the preparation of all eight stereoisomers of the C-glycoside template to enable the development of stereo/structure-activity relationships. 3b,5 Herein we describe the preparation of C-glycosides 1-4 on large (>50 g) scale.In order to introduce the ester functionality at C-1 we explored a type I Ferrier rearrangement 6 of tri-O-acetyl-D-and L-glucal to access C-glycosides 1-4. We elected to focus solely on optimizing the large-scale Ferrier reaction for the glucal series with the intention of accessing the galactal-derived material (2) via Mitsunobu inversion of the C-4 allylic alcohol. 7,8 Since we discovered that the α-and β-glycosides could be easily separated by silica gel chromatography and we required access to equal quantities of both anomers, we elected to develop reaction conditions that would achieve a closer to 1:1 α/β ratio.As shown in Table 1, we evaluated the Ferrier reaction of tri-O-acetyl-D-glucal with 5 under a range of conditions, mainly focused on varying the nature of the Lewis acid and solvent. Use of BF 3 ·Et 2 O as the Lewis acid in CH 2 Cl 2 led to the formation of C-glycoside 6 in 45% yield as a 1:2 mixture of anomers favoring the β-anomer (entry 1). Changing the Lewis acid to TMSOTf led to a higher isolated yield (73%) and a more favorable ratio of anomers 1:1.5 (entry 2). Using TMSOTf we next investigated the effect of solvent on reaction selectivity. When employing CH 3 CN as a solvent the formation of the α-anomer was slightly favored (α/β ratio = 1.5:1) and a lower yield was obtained (65%, entry 3). The yield of the glycosidation reaction could be improved to 77% on large scale (200 g), using CH 2 Cl 2 as a co-solvent (entries 4 and 5), providing a 1.2:1 mixture of anomers. The α/β isomers could be easily separated by silica gel chromatography to provide 42% of the α-anomer (α-D-6) and 35% of the β-anomer (β-D-6). 14 Deacetylation an...

Aging is associated with reduced muscle mass (sarcopenia) and poor bone quality (osteoporosis), which together increase the incidence of falls and bone fractures. It is widely appreciated that aging triggers systemic oxidative stress, which can impair myoblast cell survival and differentiation. We previously reported that arginase plays an important role in oxidative stress-dependent bone loss. We hypothesized that arginase activity is dysregulated with aging in muscles and may be involved in muscle pathophysiology. To investigate this, we analyzed arginase activity and its expression in skeletal muscles of young and aged mice. We found that arginase activity and arginase 1 expression were significantly elevated in aged muscles. We also demonstrated that SOD2, GPx1, and NOX2 increased with age in skeletal muscle. Most importantly, we also demonstrated elevated levels of peroxynitrite formation and uncoupling of eNOS in aged muscles. Our in vitro studies using C2C12 myoblasts showed that the oxidative stress treatment increased arginase activity, decreased cell survival, and increased apoptotic markers. These effects were reversed by treatment with an arginase inhibitor, 2(S)-amino-6-boronohexanoic acid (ABH). Our study provides strong evidence that L-arginine metabolism is altered in aged muscle and that arginase inhibition could be used as a novel therapeutic target for age-related muscle complications.