Natural and Bioinspired Lipidic Alkynylcarbinols as Leishmanicidal, Antiplasmodial, Trypanocidal, Fungicidal, Antibacterial, and Antimycobacterial Agents.

The present review article recapitulates for the first time the antipathogenic biological data of a series of lipidic natural products and synthetic analogues thereof characterized by the presence in their structure of an alkynylcarbinol unit. The cytotoxic properties of such natural and bioinspired compounds have been covered by several literature overviews, but to date, no review article detailing their activity against pathogens has been proposed. This article thus aims at providing a comprehensive overview of the field including early studies from the 1970s and 1980s with a specific focus on results published from the late 1990s until nowadays.

Synthesis and biological evaluation of natural methyl ester, lactone and their synthetic analogs.

(2)- methyl ester and (4)- lactone were recently identified as major components in essential oils and extracts of from Togo. Extended biological evaluation of these acetylenic compounds was however hampered by the reduced amounts isolated. A synthetic route was designed providing access to larger quantities of these two natural products as well as to original non-natural analogs with the prospect of exploring for the first time the structure-activity relationships in this series.

Multivalent pyrrolidines acting as pharmacological chaperones against Gaucher disease.

A concise asymmetric synthesis of clickable enantiomeric pyrrolidines was achieved using Crabbé-Ma allenation. The synthesized iminosugars were grafted by copper-free strain-promoted alkyne-azide cycloaddition onto phosphorus dendrimers. The hexavalent and dodecavalent pyrrolidines were evaluated as β-glucocerebrosidase inhibitors.

Phenyl dialkynylcarbinols, a Bioinspired Series of Synthetic Antitumor Acetylenic Lipids.

A series of 25 chiral anti-cancer lipidic alkynylcarbinols (LACs) were devised by introducing an (hetero)aromatic ring between the aliphatic chain and the dialkynylcarbinol warhead. The resulting phenyl-dialkynylcarbinols (PACs) exhibit enhanced stability, while retaining cytotoxicity against HCT116 and U2OS cell lines with IC down to 40 nM for resolved eutomers. A clickable probe was used to confirm the PAC prodrug behavior: upon enantiospecific bio-oxidation of the carbinol by the HSD17B11 short-chain dehydrogenase/reductase (SDR), the resulting ynones covalently modify cellular proteins, leading to endoplasmic reticulum stress, ubiquitin-proteasome system inhibition, and apoptosis.

Phosphorus Dendrimers for Metal-Free Ligation: Design of Multivalent Pharmacological Chaperones against Gaucher Disease.

The first phosphorus dendrimers built on a cyclotriphosphazene core and decorated with six or twelve monofluorocyclooctyne units were prepared. A simple stirring allowed the grafting of N-hexyl deoxynojirimycin inhitopes onto their surface by copper-free strain promoted alkyne-azide cycloaddition click reaction. The synthesized iminosugars clusters were tested as multivalent inhibitors of the biologically relevant enzymes β-glucocerebrosidase and acid α-glucosidase, involved in Gaucher and Pompe lysosomal storage diseases, respectively.

SDR enzymes oxidize specific lipidic alkynylcarbinols into cytotoxic protein-reactive species.

Hundreds of cytotoxic natural or synthetic lipidic compounds contain chiral alkynylcarbinol motifs, but the mechanism of action of those potential therapeutic agents remains unknown. Using a genetic screen in haploid human cells, we discovered that the enantiospecific cytotoxicity of numerous terminal alkynylcarbinols, including the highly cytotoxic dialkynylcarbinols, involves a bioactivation by HSD17B11, a short-chain dehydrogenase/reductase (SDR) known to oxidize the C-17 carbinol center of androstan-3-alpha,17-beta-diol to the corresponding ketone. A similar oxidation of dialkynylcarbinols generates dialkynylketones, that we characterize as highly protein-reactive electrophiles.

Fragment-Based Ligand Discovery Applied to the Mycolic Acid Methyltransferase Hma (MmaA4) from : A Crystallographic and Molecular Modelling Study.

The mycolic acid biosynthetic pathway represents a promising source of pharmacological targets in the fight against tuberculosis. In , mycolic acids are subject to specific chemical modifications introduced by a set of eight S-adenosylmethionine dependent methyltransferases. Among these, Hma (MmaA4) is responsible for the introduction of oxygenated modifications.

Pharmacological Chaperone Therapy for Pompe Disease.

Pompe disease (PD), a lysosomal storage disease, is caused by mutations of the GAA gene, inducing deficiency in the acid alpha-glucosidase (GAA). This enzymatic impairment causes glycogen burden in lysosomes and triggers cell malfunctions, especially in cardiac, smooth and skeletal muscle cells and motor neurons. To date, the only approved treatment available for PD is enzyme replacement therapy (ERT) consisting of intravenous administration of GAA.

Phosphopantetheinyl transferase binding and inhibition by amidino-urea and hydroxypyrimidinethione compounds.

Owing to their role in activating enzymes essential for bacterial viability and pathogenicity, phosphopantetheinyl transferases represent novel and attractive drug targets. In this work, we examined the inhibitory effect of the aminido-urea 8918 compound against the phosphopantetheinyl transferases PptAb from Mycobacterium abscessus and PcpS from Pseudomonas aeruginosa, two pathogenic bacteria associated with cystic fibrosis and bronchiectasis, respectively. Compound 8918 exhibits inhibitory activity against PptAb but displays no activity against PcpS in vitro, while no antimicrobial activity against Mycobacterium abscessus or Pseudomonas aeruginosa could be detected.

Concise asymmetric synthesis of new enantiomeric -alkyl pyrrolidines acting as pharmacological chaperones against Gaucher disease.

A concise and asymmetric synthesis of the enantiomeric pyrrolidines 2 and ent-2 are herein reported. Both enantiomers were assessed as β-GCase inhibitors. While compound ent-2 acted as a poor competitive inhibitor, its enantiomer 2 proved to be a potent non-competitive inhibitor.

Isolation and identification of ten new sildenafil derivatives in an alleged herbal supplement for sexual enhancement.

A sexual enhancer dietary supplement in pre-commercialization phase was analyzed. It contained the two phosphodiesterase-5 inhibitors (PDE-5i) sildenafil and methisosildenafil as major adulterants. Fourteen more sildenafil derivatives were detected and after isolation, their structures were elucidated thanks to NMR, high resolution and tandem mass spectrometry, and UV spectroscopy.

Second-Generation Pharmacological Chaperones: Beyond Inhibitors.

Protein misfolding induced by missense mutations is the source of hundreds of conformational diseases. The cell quality control may eliminate nascent misfolded proteins, such as enzymes, and a pathological loss-of-function may result from their early degradation. Since the proof of concept in the 2000s, the bioinspired pharmacological chaperone therapy became a relevant low-molecular-weight compound strategy against conformational diseases.

N,O-Dialkyl deoxynojirimycin derivatives as CERT START domain ligands.

Dysregulation of the ceramide transport protein CERT is associated to diseases such as cancer. In search for new CERT START domain ligands, N-dodecyl-deoxynojirimycin (N-dodecyl-DNJ) iminosugar was found to display, as a ceramide mimic, significant protein recognition. To reinforce the lipophilic interactions and strengthen this protein binding, a docking study was carried out in order to select the optimal position on which to introduce an additional O-alkyl chain on N-dodecyl-DNJ.

Selective Targeting of the Interconversion between Glucosylceramide and Ceramide by Scaffold Tailoring of Iminosugar Inhibitors.

A series of simple -alkyl pyrrolidines already known as cytotoxic inhibitors of ceramide glucosylation in melanoma cells can be converted into their corresponding 6-membered analogues by means of a simple ring expansion. This study illustrated how an isomerisation from iminosugar pyrrolidine toward piperidine could invert their targeting from glucosylceramide (GlcCer) formation toward GlcCer hydrolysis. Thus, we found that the 5-membered ring derivatives did not inhibit the hydrolysis reaction of GlcCer catalysed by lysosomal β-glucocerebrosidase (GBA).

Alkyne-Tagged Analogue of Jaspine B: New Tool for Identifying Jaspine B Mode of Action.

The first biologically relevant clickable probe related to the antitumor marine lipid jaspine B is reported. The concise synthetic route to both enantiomers relied on the supercritical fluid chromatography (SFC) enantiomeric resolution of racemic materials. The eutomeric dextrogyre derivative represents the first jaspine B analogue with enhanced cytotoxicity with IC down to 30 nm.

Methinylogation Approach in Chiral Pharmacophore Design: from Alkynyl- to Allenyl-carbinol Warheads against Tumor Cells.

Extension of a structure-activity relationship study of the antitumor cytotoxicity of lipidic dialkynylcarbinols (DACs) is envisaged by formal methinylogation of one of the ethyndiyl moieties of the DAC warhead into the corresponding allenylalkynylcarbinol (AllAC) counterpart. External AllACs were directly obtained by methinylation of the parent DACs with formaldehyde in either the racemic or scalemic series. Isomers containing external progargyl and propynyl motifs were also prepared.

Skeletal Optimization of Cytotoxic Lipidic Dialkynylcarbinols.

In line with a recent study of the pharmacological potential of bioinspired synthetic acetylenic lipids, after identification of the terminal dialkynylcarbinol (DAC) and butadiynyl alkynylcarbinol (BAC) moieties as functional antitumor pharmacophoric units, this work specifically addresses the issue of carbon backbone length. A systematic variation of the aliphatic chain length was thus carried out in both the DAC and BAC series. The critical impact of the length of the lipidic skeleton was first confirmed in the racemic series, with the highest cytotoxic activity observed for C to C backbones.

Iminosugar-based ceramide mimicry for the design of new CERT START domain ligands.

The enigmatical dichotomy between the two CERT/GPBP protein isoforms, their vast panel of biological implications and the scarcity of known antagonist series call for new ligand chemotypes identification. We report the design of iminosugar-based ceramide mimics for the development of new START domain ligands potentially targeting either protein isoforms. Strategic choice of (i) an iminoxylitol core structure and (ii) the positioning of two dodecyl residues led to an extent of protein binding comparable to that of the natural cargo lipid ceramide or the archetypical inhibitor HPA-12.

Chemistry and Biology of HPAs: A Family of Ceramide Trafficking Inhibitors.

In 2001, two years before the disclosure of the CERT-associated Cer transfer machinery, N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)alkanamides (HPAs) were described as the first, and to date unique, family of intracellular Cer trafficking inhibitors. The dodecanamide derivative, HPA-12, turned out to be a benchmark as a cellular inhibitor of CERT-mediated de novo sphingomyelin biosynthesis. In only 15 years after its first disclosure, this compound has prompted a growing number of biological and chemical studies.

Asymmetric Synthesis and Binding Study of New Long-Chain HPA-12 Analogues as Potent Ligands of the Ceramide Transfer Protein CERT.

A series of 12 analogues of the Cer transfer protein (CERT) antagonist HPA-12 with long aliphatic chains were prepared as their (1R,3S)-syn and (1R,3R)-anti stereoisomers from pivotal chiral oxoamino acids. The enantioselective access to these intermediates as well as their ensuing transformation relied on a practical crystallization-induced asymmetric transformation (CIAT) process. Sonogashira coupling followed by triple bond reduction and thiophene ring hydrodesulfurization (HDS) into the corresponding alkane moieties was then implemented to complete the synthetic routes delivering the targeted HPA-12 analogues in concise 4- to 6-step reaction sequences.

Fluorophore-tagged pharmacophores for antitumor cytotoxicity: Modified chiral lipidic dialkynylcarbinols for cell imaging.

Chiral lipidic dialkynylcarbinols (DACs), recently highlighted as antitumoral pharmacophores, have been conjugated to difluoroboron-dipyrromethene (bodipy), 7-hydroxy-coumarine, and 7-nitro-benzoxadiazole (NBD) fluorophore motifs through triazole clips. The labeled lipids preserve cytotoxic activity against HCT116 cells, and fluorescence microscopy of the stained cells showed clear signals in the intra-cellular membrane system. While the bodipy conjugate also labels lipid droplets very brightly, as expected, the coumarine and NBD probes appear as promising specific tools for the identification of the intra-cellular targets of DACs' cytotoxicity.

A novel jaspine B-ceramide hybrid modulates sphingolipid metabolism.

A new sphingolipid hybrid molecule was designed to assemble, within a tail-to-tail double-chain structure, the ceramide hydrophilic moiety and the tetrahydrofuran pharmacophore of jaspine B, a natural product known to interfere with sphingolipid metabolism. This compound was prepared through acylation of sphingosine with a jaspine B derivative bearing a COOH group in the terminal position of the aliphatic backbone. This new hybrid molecule was evaluated for its capacities to affect melanoma cell viability and sphingolipid metabolism.

Asymmetric synthesis and biological evaluation of natural or bioinspired cytotoxic C2-symmetrical lipids with two terminal chiral alkynylcarbinol pharmacophores.

Bidirectional syntheses of C2-symmetrical lipids embedding two terminal alkynylcarbinol pharmacophores are reported. Naturally occurring chiral alkenylalkynylcarbinol units were generated using Pu's procedure for enantioselective addition of terminal alkynes to aldehydes, allowing the first asymmetric synthesis of (3R,4E,16E,18R)-icosa-4,16-diene-1,19-diyne-3,18-diol, isolated from Callyspongia pseudoreticulata. Two synthetic analogues embedding the recently uncovered (S)-dialkynylcarbinol pharmacophore were secured using Carreira's procedure adapted to ynal substrates.

Development of a CERT START Domain-Ceramide HTRF Binding Assay and Application to Pharmacological Studies and Screening.

Sphingomyelin (SM) metabolism deregulation was recently associated with cell metastasis and chemoresistance, and several pharmacological strategies targeting SM metabolism have emerged. The ceramide (Cer) generated in the endoplasmic reticulum (ER) is transferred to the Golgi apparatus to be transformed into SM. CERamide Transfer (CERT) protein is responsible for the nonvesicular trafficking of Cer to Golgi.