Sulfamates and their therapeutic potential

Natural Products Containing a Nitrogen-Sulfur Bond

Only about 100 natural products are known to contain a nitrogen-sulfur (N-S) bond. This review thoroughly categorizes N-S bond-containing compounds by structural class. Information on biological source, biological activity, and biosynthesis is included, if known. We also review the role of N-S bond functional groups as post-translational modifications of amino acids in proteins and peptides, emphasizing their role in the metabolism of the cell.

Cyclic imines – preparation and application in synthesis

Cyclic imines, available from various nitrogen-containing reactants, serve as versatile synthetic intermediates for biologically active compounds.

Pd-Catalyzed diastereoselective [3 + 2] cycloaddition of vinylcyclopropanes with sulfamate-derived cyclic imines

The palladium-catalyzed diastereoselective [3 + 2] cycloaddition reaction of vinylcyclopropanes with sulfamate-derived cyclic imines worked efficiently under mild conditions, providing sulfamate-fused pyrrolidines in good to excellent yields.

Insights into the binding mode of sulphamates and sulphamides to hCA II: crystallographic studies and binding free energy calculations

Sulphamate and sulphamide derivatives have been largely investigated as carbonic anhydrase inhibitors (CAIs) by means of different experimental techniques. However, the structural determinants responsible for their different binding mode to the enzyme active site were not clearly defined so far. In this paper, we report the X-ray crystal structure of hCA II in complex with a sulphamate inhibitor incorporating a nitroimidazole moiety. The comparison with the structure of hCA II in complex with its sulphamide analogue revealed that the two inhibitors adopt a completely different binding mode within the hCA II active site. Starting from these results, we performed a theoretical study on sulphamate and sulphamide derivatives, demonstrating that electrostatic interactions with residues within the enzyme active site play a key role in determining their binding conformation. These findings open new perspectives in the design of effective CAIs using the sulphamate and sulphamide zinc binding groups as lead compounds.

Synthesis of N-Substituted Sulfamate Esters from Sulfamic Acid Salts by Activation with Triphenylphosphine Ditriflate

A general approach to access sulfamate esters through preparation of sulfamic acid salts, subsequent activation with triphenylphosphine ditriflate, and nucleophilic trapping is disclosed. The method proceeds in modest to excellent yields to incorporate nucleophiles derived from aliphatic alcohols and phenols. This approach can be employed to furnish differentially substituted sulfamides.

Improving the carbonic anhydrase inhibition profile of the sulfamoylphenyl pharmacophore by attachment of carbohydrate moieties

One of the most successful approaches for designing carbonic anhydrase (CA, EC 4.2.1.1) inhibitors was denominated 'the sugar approach'. The sugar approach consists in attaching different carbohydrates to CA inhibiting pharmacophores for modulating the physicochemical properties of these pharmacological agents. In line with this approach, in this paper, we present a new class of C-glycosides incorporating the sulfamoylphenyl moiety. These compounds have been prepared by sulfamoylation of C-glycosyl phenols, which have been synthetized by aldol reaction of glycosyl ketones with the appropriate aromatic aldehydes. The inhibition profile of the new glycomimetics was determined against four human (h) CA isozymes, comprising hCAs I and II (cytosolic, ubiquitous isozymes), hCA IV and hCA IX (tumor associated isozyme). Peracetylated and deprotected C-glycosyl sulfamates showed better inhibition selectivity compared to structurally related phenylsulfamates. In this study, deprotected compound 12 was identified as selective inhibitor of hCA IX. These results confirm that attaching carbohydrate moieties to CA sulfamoylphenyl pharmacophore improves its inhibitory activity.

Probing Molecular Interactions between Human Carbonic Anhydrases (hCAs) and a Novel Class of Benzenesulfonamides

On the basis of X-ray crystallographic studies of the complex of hCA II with 4-(3,4-dihydro-1H-isoquinoline-2-carbonyl)benzenesulfonamide (3) (PDB code 4Z1J ), a novel series of 4-(1-aryl-3,4-dihydro-1H-isoquinolin-2-carbonyl)benzenesulfonamides (23-33) was designed. Specifically, our idea was to improve the selectivity toward druggable isoforms through the introduction of additional hydrophobic/hydrophilic functionalities. Among the synthesized and tested compounds, the (R,S)-4-(6,7-dihydroxy-1-phenyl-3,4-tetrahydroisoquinoline-1H-2-carbonyl)benzenesulfonamide (30) exhibited a remarkable inhibition for the brain-expressed hCA VII (Ki = 0.20 nM) and selectivity over wider distributed hCA I and hCA II isoforms. By enantioselective HPLC, we solved the racemic mixture and ascertained that the two enantiomers (30a and 30b) are equiactive inhibitors for hCA VII. Crystallographic and docking studies revealed the main interactions of these inhibitors into the carbonic anhydrase (CA) catalytic site, thus highlighting the relevant role of nonpolar contacts for this class of hCA inhibitors.

Use of azidonaphthalimide carboxylic acids as fluorescent templates with a built-in photoreactive group and a flexible linker simplifies protein labeling studies: applications in selective tagging of HCAII and penicillin binding proteins

A simple design of versatile template-based protein labeling agents has been successfully demonstrated with HCA and PBPs.

Enediyne-based protein capture agents: demonstration of an enediyne moiety acting as a photoaffinity label

Two enediyne based protein-capture compounds 1 and 2 were synthesized.

An asymmetric Brønsted acid-catalyzed Friedel–Crafts reaction of indoles with cyclic N-sulfimines

A highly enantioselective organocatalytic Friedel–Crafts reaction of indoles with cyclic N-sulfimines using a chiral phosphoric acid as an organocatalyst has been developed.

Synthesis, functionalization and biological activity of arylated derivatives of (+)-estrone

Various novel arylated estrone derivatives, such as 2-aryl-, 4-aryl- and 2,4-diaryl-estrones, by Suzuki-Miyaura reactions. While the synthesis of 4-arylestrones could be carried out under standard conditions, the synthesis of 2-arylestrones and 2,4-diarylestrones required a thorough optimization of the conditions and it proved to be important to use sterically encumbered biaryl ligands. The best results were obtained by the use of RuPhos. Combination of developed Suzuki coupling reactions with subsequent cyclization reactions afforded more complex hybrid structures, containing dibenzofuran, benzocoumarin and steroid moieties. These derivatives were tested as pancreatic lipase inhibitors and it was found that most of the compounds exhibited inhibition of pancreatic lipase but the maximum inhibitory potential was shown by 4-arylestrones. All of the synthesized derivatives showed inhibitory values in the range of 0.82±0.01-59.7±3.12μM. The biological activity was also rationalized on the bases of docking studies.

Autophagy induced by a sulphamoylated estrone analogue contributes to its cytotoxic effect on breast cancer cells

Background

Autophagy can either be protective and confer survival to stressed cells, or it can contribute to cell death. The antimitotic drug 2-ethyl-3-O-sulpamoyl-estra-1,3,5(10),15-tetraen-17-ol (ESE-15-ol) is an in silico-designed 17-β-estradiol analogue that induces both autophagy and apoptosis in cancer cells. The aim of the study was to determine the role of autophagy in ESE-15-ol-exposed human adenocarcinoma breast cancer cells; knowledge that will contribute to future clinical applications of this novel antimitotic compound. By inhibiting autophagy and determining the cytotoxic effects of ESE-15-ol-exposure, deductions could be made as to whether the process may confer resistance to the drug, or alternatively, contribute to the cell death process.

Methods and results

Spectophometrical analysis via crystal violet staining was used to perform cytotoxicity studies. Morphology studies were done using microscopic techniques namely polarization-optical transmitted light differential interference light microscopy, fluorescent microscopy using monodansylcadaverine staining and transmission electron microscopy. Flow cytometry was used to quantify the autophagy inhibition and assess cell viability. Results obtained indicated that 3-methyladenine inhibited autophagy and increased cell survival in both MCF-7 and MDA-MB-231 cell lines.

Conclusion

This in vitro study inferred that autophagy inhibition with 3-methyladenine does not confer increased effectiveness of ESE-15-ol in inducing cell death. Thus it may be concluded that the autophagic process induced by ESE-15-ol exposure in MCF-7 and MDA-MB-231 cells plays a more significant role in cell death than conferring survival.

Initial Testing of NSC 750854, a Novel Purine Analog, Against Pediatric Tumor Models by the Pediatric Preclinical Testing Program

BACKGROUND

NSC 750854 is a purine analog with an antitumor activity profile distinctive from that of other anticancer purines. It has shown significant activity against adult cancer preclinical models.

PROCEDURE

NSC 750854 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro cell line panel at concentrations from 1.0 nM to 10 μM and against the PPTP in vivo xenograft panels administered intraperitoneally at a dose of 5 mg/kg daily for 5 days repeated at day 15.

RESULTS

The median relative IC50 (rIC50 ) value for the PPTP cell lines was 32 nM (range from 11 to 124 nM), with consistent cytotoxicity across all cell lines. Acute lymphoblastic leukemia (ALL) cell lines were more sensitive to NSC 750854 than non-ALL cell lines. NSC 750854 induced significant differences in EFS distribution compared to control in 31 of 35 (89%) solid tumor xenografts. It induced tumor growth inhibition meeting criteria for intermediate or high event free survival (EFS) T/C activity in 17 of 32 (53%) evaluable solid tumor xenografts (most consistently in the rhabdomyosarcoma panel). Objective responses were observed in 15 of 37 (41%) solid tumor xenografts and in all eight leukemia models with complete response (CR) or maintained complete response (MCR) in seven of eight leukemia models.

CONCLUSIONS

NSC 750854 has a unique spectrum of antitumor activity compared with other agents tested by the PPTP as it induces regression in tumor models with limited sensitivity to most agents tested to date. Given the promising level of activity observed for NSC 750854 against PPTP preclinical models, further exploration of its mechanism of action is warranted.

New metal extractants and super-acidic ionic liquids derived from sulfamic acid

N-Alkylated sulfamic acid derivatives are very interesting for metal processing. A new class of metal extractants and super-acidic ionic liquids is introduced.

Betulinyl Sulfamates as Anticancer Agents and Radiosensitizers in Human Breast Cancer Cells

Betulinic acid (BA), a natural compound of birch bark, is cytotoxic for many tumors. Recently, a betulinyl sulfamate was described that inhibits carbonic anhydrases (CA), such as CAIX, an attractive target for tumor-selective therapy strategies in hypoxic cancer cells. Data on combined CAIX inhibition with radiotherapy are rare. In the human breast cancer cell lines MDA-MB231 and MCF7, the effects of BA and betulinyl sulfamates on cellular and radiobiological behavior under normoxia and hypoxia were evaluated. The two most effective betulinyl sulfamates CAI 1 and CAI 3 demonstrated a 1.8–2.8-fold higher cytotoxicity than BA under normoxia in breast cancer cells, with IC₅₀ values between 11.1 and 18.1 µM. BA exhibits its strongest cytotoxicity with IC₅₀ values of 8.2 and 16.4 µM under hypoxia. All three substances show a dose-dependent increase in apoptosis, inhibition of migration, and inhibition of hypoxia-induced gene expression. In combination with irradiation, betulinyl sulfamates act as radiosensitizers, with DMF10 values of 1.47 (CAI 1) and 1.75 (CAI 3) under hypoxia in MDA-MB231 cells. BA showed additive effects in combination with irradiation. Taken together; our results suggest that BA and betulinyl sulfamates seem to be attractive substances to combine with radiotherapy; particularly for hypoxic breast cancer.

Discovery and Development of the Aryl O-Sulfamate Pharmacophore for Oncology and Women's Health

In 1994, following work from this laboratory, it was reported that estrone-3-O-sulfamate irreversibly inhibits a new potential hormone-dependent cancer target steroid sulfatase (STS). Subsequent drug discovery projects were initiated to develop the core aryl O-sulfamate pharmacophore that, over some 20 years, have led to steroidal and nonsteroidal drugs in numerous preclinical and clinical trials, with promising results in oncology and women's health, including endometriosis. Drugs have been designed to inhibit STS, e.g., Irosustat, as innovative dual-targeting aromatase-steroid sulfatase inhibitors (DASIs) and as multitargeting agents for hormone-independent tumors, such as the steroidal STX140 and nonsteroidal counterparts, acting inter alia through microtubule disruption. The aryl sulfamate pharmacophore is highly versatile, operating via three distinct mechanisms of action, and imbues attractive pharmaceutical properties. This Perspective gives a personal view of the work leading both to the therapeutic concepts and these drugs, their current status, and how they might develop in the future.

Estrogen O-sulfamates and their analogues: Clinical steroid sulfatase inhibitors with broad potential

Estrogen sulfamate derivatives were the first irreversible active-site-directed inhibitors of steroid sulfatase (STS), an emerging drug target for endocrine therapy of hormone dependent diseases that catalyzes inter alia the hydrolysis of estrone sulfate to estrone. In recent years this has stimulated clinical investigation of the estradiol derivative both as an oral prodrug and its currently ongoing exploration in endometriosis. 2-Substituted steroid sulfamate derivatives show considerable potential as multi-targeting agents for hormone-independent disease, but are also potent STS inhibitors. The steroidal template has spawned nonsteroidal STS inhibitors one of which, Irosustat, has been evaluated clinically in breast cancer, endometrial cancer and prostate cancer and there is potential for innovative dual-targeting approaches. This review surveys the role of estrogen sulfamates, their analogues and current status.

Malaria parasite carbonic anhydrase: inhibition of aromatic/heterocyclic sulfonamides and its therapeutic potential

Plasmodium falciparum (P. falciparum) is responsible for the majority of life-threatening cases of human malaria, causing 1.5-2.7 million annual deaths. The global emergence of drug-resistant malaria parasites necessitates identification and characterization of novel drug targets and their potential inhibitors. We identified the carbonic anhydrase (CA) genes in P. falciparum. The pfCA gene encodes anα-carbonic anhydrase, a Zn(2+)-metalloenzme, possessing catalytic properties distinct from that of the human host CA enzyme. The amino acid sequence of the pfCA enzyme is different from the analogous protozoan and human enzymes. A library of aromatic/heterocyclic sulfonamides possessing a large diversity of scaffolds were found to be very good inhibitors for the malarial enzyme at moderate-low micromolar and submicromolar inhibitions. The structure of the groups substituting the aromatic-ureido- or aromatic-azomethine fragment of the molecule and the length of the parent sulfonamide were critical parameters for the inhibitory properties of the sulfonamides. One derivative, that is, 4- (3, 4-dichlorophenylureido)thioureido-benzenesulfonamide (compound 10) was the most effective in vitro Plasmodium falciparum CA inhibitor, and was also the most effective antimalarial compound on the in vitro P. falciparum growth inhibition. The compound 10 was also effective in vivo antimalarial agent in mice infected with Plasmodium berghei, an animal model of drug testing for human malaria infection. It is therefore concluded that the sulphonamide inhibitors targeting the parasite CA may have potential for the development of novel therapies against human malaria.

Hydrophobic substituents of the phenylmethylsulfamide moiety can be used for the development of new selective carbonic anhydrase inhibitors

A new series of compounds containing a sulfamide moiety as zinc-binding group (ZBG) has been synthesized and tested for determining inhibitory properties against four human carbonic anhydrase (hCA) isoforms, namely, CAs I, II, IX, and XII. The X-ray structure of the cytosolic dominant isoform hCA II in complex with the best inhibitor of the series has also been determined providing further insights into sulfamide binding mechanism and confirming that such zinc-binding group, if opportunely derivatized, can be usefully exploited for obtaining new potent and selective CAIs. The analysis of the structure also suggests that for drug design purposes the but-2-yn-1-yloxy moiety tail emerges as a very interesting substituent of the phenylmethylsulfamide moiety due to its capability to establish strong van der Waals interactions with a hydrophobic cleft on the hCA II surface, delimited by residues Phe131, Val135, Pro202, and Leu204. Indeed, the complementarity of this tail with the cleft suggests that different substituents could be used to discriminate between isoforms having clefts with different sizes.

Managing abnormal eating behaviours in frontotemporal lobar degeneration patients with topiramate

Abnormal eating behaviours are specific to frontotemporal lobar degeneration and increase caregiver burden. Topiramate, an anticonvulsant, suppresses cravings for alcohol and other substances and is a potential treatment for binge eating. However, there are few reports on topiramate efficacy for abnormal eating behaviours in frontotemporal lobar degeneration patients. We present three Japanese frontotemporal lobar degeneration patients with abnormal eating behaviours. Topiramate was effective, especially for compulsive eating, in cases with distinct lobar atrophy, but not for all abnormal eating behaviours.

In vitro evaluation of ESE-15-ol, an estradiol analogue with nanomolar antimitotic and carbonic anhydrase inhibitory activity

Antimitotic compounds are still one of the most widely used chemotherapeutic anticancer drugs in the clinic today. Given their effectiveness against cancer it is beneficial to continue enhancing these drugs. One way is to improve the bioavailability and efficacy by synthesizing derivatives that reversibly bind to carbonic anhydrase II (CAII) in red blood cells followed by a slow release into the blood circulation system. In the present study we describe the in vitro biological activity of a reduced derivative of 2-ethyl-3-O-sulphamoyl-estradiol (2EE), 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10),15-tetraen-17-ol (ESE-15-ol). ESE-15-ol is capable of inhibiting carbonic anhydrase activity in the nanomolar range and is selective towards a mimic of carbonic anhydrase IX when compared to the CAII isoform. Docking studies using Autodock Vina suggest that the dehydration of the D-ring plays a role towards the selectivity of ESE-15-ol to CAIX and that the binding mode of ESE-15-ol is substantially different when compared to 2EE. ESE-15-ol is able to reduce cell growth to 50% after 48 h at 50–75 nM in MCF-7, MDA-MB-231, and MCF-12A cells. The compound is the least potent against the non-tumorigenic MCF-12A cells. In vitro mechanistic studies demonstrate that the newly synthesized compound induces mitochondrial membrane depolarization, abrogates the phosphorylation status of Bcl-2 and affects gene expression of genes associated with cell death and mitosis.

Medicinal significance of benzothiazole scaffold: an insight view

Heterocycles bearing nitrogen, sulphur and thiazole moieties constitute the core structure of a number of biologically interesting compounds. Benzothiazole, a group of xenobiotic compounds containing a benzene ring fused with a thiazole ring, are used worldwide for a variety of therapeutic applications. Benzothiazole and their heterocyclic derivatives represent an important class of compounds possessing a wide spectrum of biological activities. The myriad spectrum of medicinal properties associated with benzothiazole related drugs has encouraged the medicinal chemists to synthesize a large number of novel therapeutic agents. Several analogues containing benzothiazole ring system exhibit significant antitumour, antimicrobial, antidiabetic, anti-inflammatory, anticonvulsant, antiviral, antioxidant, antitubercular, antimalarial, antiasthmatic, anthelmintic, photosensitizing, diuretic, analgesic and other activities. This article is an attempt to present the research work reported in recent scientific literature on different pharmacological activities of benzothiazole compounds.