Adelphe M. Mfuh

Direct, Catalytic, and Regioselective Synthesis of 2-Alkyl-, Aryl-, and Alkenyl-Substituted N-Heterocycles from N-Oxides

A one-step transformation of heterocyclic N-oxides to 2-alkyl-, aryl-, and alkenyl-substituted N-heterocycles is described. The success of this broad-scope methodology hinges on the combination of copper catalysis and activation by lithium fluoride or magnesium chloride. The utility of this method for the late-stage modification of complex N-heterocycles is exemplified by facile syntheses of new structural analogues of several antimalarial, antimicrobial, and fungicidal agents.

Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium Salts.

We report herein a simple, metal- and additive-free, photoinduced borylation of haloarenes, including electron-rich fluoroarenes, as well as arylammonium salts directly to boronic acids. This borylation method has a broad scope and functional group tolerance. We show that it can be further extended to boronic esters and carried out on gram scale as well as under flow conditions.

Adsorption of proteins to thin-films of PDMS and its effect on the adhesion of human endothelial cells

This paper describes a simple and inexpensive procedure to produce thin-films of poly(dimethylsiloxane). Such films were characterized by a variety of techniques (ellipsometry, nuclear magnetic resonance, atomic force microscopy, and goniometry) and used to investigate the adsorption kinetics of three model proteins (fibrinogen, collagen type-I, and bovine serum albumin) under different conditions. The information collected from the protein adsorption studies was then used to investigate the adhesion of human dermal microvascular endothelial cells. The results of these studies suggest that these films can be used to model the surface properties of microdevices fabricated with commercial PDMS. Moreover, the paper provides guidelines to efficiently attach cells in BioMEMS devices.

Additive- and Metal-Free, Predictably 1,2- and 1,3-Regioselective, Photoinduced Dual C–H/C–X Borylation of Haloarenes

We report herein a simple, additive- and metal-free, photoinduced, dual C-H/C-X borylation of chloro-, bromo-, and iodoarenes. The reaction produces 1,2- and 1,3-diborylarenes on gram scales under batch and continuous flow conditions. The regioselectivity of the dual C-H/C-X borylation is determined by the solvent and the substituents in the parent haloarenes.

Heterocyclic N-Oxides – An Emerging Class of Therapeutic Agents

Heterocyclic N-oxides have emerged as potent compounds with anticancer, antibacterial, antihypertensive, antiparasitic, anti-HIV, anti-inflammatory, herbicidal, neuroprotective, and procognitive activities. The N-oxide motif has been successfully employed in a number of recent drug development projects. This review surveys the emergence of this scaffold in the mainstream medicinal chemistry with a focus on the discovery of the heterocyclic N-oxide drugs, N-oxide-specific mechanisms of action, drug-receptor interactions and synthetic avenues to these compounds. As the first review on this subject that covers the developments since 1950s to date, it is expected that it will inspire wider implementation of the heterocyclic N-oxide motif in the rational design of new medicinal agents.

Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles

A Mo/P catalytic system for an efficient gram-scale oxidation of a variety of nitrogen heterocycles to N-oxides with hydrogen peroxide as terminal oxidant has been investigated. Combined spectroscopic and crystallographic studies point to the tetranuclear Mo4P peroxo complex as one of the active catalytic species present in the solution. Based on this finding an optimized catalytic system has been developed. The utility and chemoselectivity of the catalytic system has been demonstrated by the synthesis of over 20 heterocyclic N-oxides.

Novel asparagine-derived lipid enhances distearoylphosphatidylcholine bilayer resistance to acidic conditions

A novel asparagine-derived lipid analogue (ALA(11,17)) bearing a tetrahydropyrimidinone headgroup and two fatty chains (11 and 17 indicate the lengths of linear alkyl groups) was synthesized in high yield and purity. The thin film hydration of formulations containing 5 mol % or greater ALA(11,17) in distearoylphosphatidylcholine (DSPC) generated multilamellar vesicles (MLVs) that remained unaggregated according to optical microscopy, while those formed from DSPC only were highly clustered. The MLVs were processed into unilamellar liposomes via extrusion and were characterized by dynamic light scattering (DLS), zeta potential, turbidity, and scanning electron microscopy (SEM) analysis. Results show that the presence of ALA(11,17) in DSPC liposomes significantly alters the morphology, colloidal stability, and retention of encapsulated materials in both acidic and neutral conditions. The ability of ALA(11,17)-hybrid liposomes to encapsulate and retain inclusions under neutral and acidic conditions (pH < 2) was demonstrated by calcein dequenching experiments. DLS and SEM confirmed that ALA(11,17)/DSPC liposomes remained intact under these conditions. The bilayer integrity observed under neutral and acidic conditions and the likely biocompatibility of these fatty amino acid analogues suggest that ALA(11,17) is a promising additive for modulating phosphatidylcholine lipid bilayer properties.

Concise Total Synthesis of Trichodermamides A, B, and C Enabled by an Efficient Construction of the 1,2-Oxazadecaline Core

We report herein a facile and efficient method of the construction of the cis-1,2-oxazadecaline system, distinctive of (pre)trichodermamides, aspergillazine A, gliovirin, and FA-2097. The formation of the 1,2-oxazadecaline core was accomplished by a 1,2-addition of an αC-lithiated O-silyl ethyl pyruvate oxime to benzoquinone, which is followed by an oxa-Michael ring-closure. The method was successfully applied to the concise total synthesis of trichodermamide A (in gram quantities) and trichodermamide B, as well as the first synthesis of trichodermamide C.

Cytotoxicity and Mechanism of Action of the Marine-Derived Fungal Metabolite Trichodermamide B and Synthetic Analogues

The trichodermamides are modified dipeptides isolated from a wide variety of fungi, including Trichoderma virens. Previous studies reported that trichodermamide B (2) initiated cytotoxicity in HCT-116 colorectal cancer cells, while trichodermamide A (1) was devoid of activity. We recently developed an efficient total synthesis for the trichodermamides A-C (1-3). Multiple intermediates and analogues were produced, and they were evaluated for biological effects to identify additional structure-activity relationships and the possibility that a simplified analogue would retain the biological effects of 2. The antiproliferative effects of 18 compounds were evaluated, and the results show that 2 and four other compounds are active in HeLa cells, with IC50 values in the range of 1.4-21 μM. Mechanism of action studies of 2 and the other active analogues revealed different spectra of activity. At the IC85 concentration, 2 caused S-phase accumulation and cell death in HeLa cells, suggesting response to DNA double-strand breaks. The analogues did not cause S-phase accumulation or induction of DNA damage repair pathways, consistent with an alternate mode of action. The mechanistic differences are hypothesized to be due to the chlorohydrin moiety in 2, which is lacking in the analogues, which could form a DNA-reactive epoxide.

Identification of Inhibitors of CD36-Amyloid Beta Binding as Potential Agents for Alzheimer’s Disease

Neuroinflammation is one of the hallmarks of Alzheimers disease pathology. Amyloid β has a central role in microglia activation and the subsequent secretion of inflammatory mediators that are associated with neuronal toxicity. The recognition of amyloid β by microglia depends on the expression of several receptors implicated in the clearance of amyloid and in cell activation. CD36 receptor expressed on microglia interacts with fibrils of amyloid inducing the release of proinflammatory cytokines and amyloid internalization. The interruption of the interaction CD36-amyloid β compromises the activation of microglia cells. We have developed and validated a new colorimetric assay to identify potential inhibitors of the binding of amyloid β to CD36. We have found seven molecules, structural analogues of the Trichodermamide family of natural products that interfere with the interaction CD36-amyloid β. By combining molecular docking and dynamics simulations, we suggested the second fatty acids binding site within the large luminal hydrophobic tunnel, present in the extracellular domain of CD36, as the binding pocket of these compounds. Free energy calculations predicted the nonpolar component as the driving force for the binding of these inhibitors. These molecules also inhibited the production of TNF-α, IL-6, and IL-1β by peritoneal macrophages stimulated with fibrils of amyloid β. This work serves as a platform for the identification of new potential anti-inflammatory agents for the treatment of Alzheimers disease.