Flexible synthesis and biological activity of uronic acid-type gem-diamine 1-N-iminosugars: a new family of glycosidase inhibitors

The Uptake of Heparanase into Mast Cells Is Regulated by Its Enzymatic Activity to Degrade Heparan Sulfate

Mast cells take up extracellular latent heparanase and store it in secretory granules. The present study examined whether the enzymatic activity of heparanase regulates its uptake efficiency. Recombinant mouse heparanase mimicking both the latent and mature forms (L-Hpse and M-Hpse, respectively) was internalized into mastocytoma MST cells, peritoneal cell-derived mast cells, and bone marrow-derived mast cells. The internalized amount of L-Hpse was significantly higher than that of M-Hpse. In MST cells, L-Hpse was continuously internalized for up to 8 h, while the uptake of M-Hpse was saturated after 2 h of incubation. L-Hpse and M-Hpse are similarly bound to the MST cell surface. The expression level of cell surface heparan sulfate was reduced in MST cells incubated with M-Hpse. The internalized amount of M-Hpse into mast cells was significantly increased in the presence of heparastatin (SF4), a small molecule heparanase inhibitor that does not affect the binding of heparanase to immobilized heparin. Enzymatically quiescent M-Hpse was prepared with a point mutation at Glu335. The internalized amount of mutated M-Hpse was significantly higher than that of wild-type M-Hpse but similar to that of wild-type and mutated L-Hpse. These results suggest that the enzymatic activity of heparanase negatively regulates the mast cell-mediated uptake of heparanase, possibly via the downregulation of cell surface heparan sulfate expression.

Molecular Basis for Inhibition of Heparanases and β-Glucuronidases by Siastatin B

Siastatin B is a potent and effective iminosugar inhibitor of three diverse glycosidase classes, namely, sialidases, β-d-glucuronidases, and N-acetyl-glucosaminidases. The mode of inhibition of glucuronidases, in contrast to sialidases, has long been enigmatic as siastatin B appears too bulky and incorrectly substituted to be accommodated within a β-d-glucuronidase active site pocket. Herein, we show through crystallographic analysis of protein-inhibitor complexes that siastatin B generates both a hemiaminal and a 3-geminal diol iminosugar (3-GDI) that are, rather than the parent compound, directly responsible for enzyme inhibition. The hemiaminal product is the first observation of a natural product that belongs to the noeuromycin class of inhibitors. Additionally, the 3-GDI represents a new and potent class of the iminosugar glycosidase inhibitor. To substantiate our findings, we synthesized both the gluco- and galacto-configured 3-GDIs and characterized their binding both structurally and kinetically to exo-β-d-glucuronidases and the anticancer target human heparanase. This revealed submicromolar inhibition of exo-β-d-glucuronidases and an unprecedented binding mode by this new class of inhibitor. Our results reveal the mechanism by which siastatin B acts as a broad-spectrum glycosidase inhibitor, identify a new class of glycosidase inhibitor, and suggest new functionalities that can be incorporated into future generations of glycosidase inhibitors.

Endothelial Protection in Lung Grafts through Heparanase Inhibition During Ex Vivo Lung Perfusion in Rats

OBJECTIVE

We hypothesized that enhancing glycocalyx preservation would reduce endothelial damage in lung grafts during ex-vivo lung perfusion (EVLP) leading to better transplant outcomes. In this study, we characterized the effects of inhibiting heparanase (HPSE), an enzyme responsible for glycocalyx shedding, on lung quality during EVLP.

METHODS

Human clinical EVLP perfusate from lung graft patients was utilized to identify a potential association between glycocalyx integrity in grafted lung tissue and clinical data. In addition, we performed pre-clinical studies in which rat lungs underwent normothermic EVLP for 4 hours with/without HPSE inhibitors, heparin (1000-U/hour) or heparastatin (SF4; 1-μM), added to the perfusate. After 4-hours EVLP, left lungs were transplanted into syngeneic rats then evaluated for graft quality 2-hours after reperfusion.

RESULTS

Clinically, increased degradation of syndecan-1 was identified in dysfunctional grafts during EVLP. Levels of heparan sulfate in perfusate after EVLP were associated with incidence of graft dysfunction after transplantation. In the pre-clinical rat study, SF4 effectively inhibited HPSE activity, and significantly attenuated dissociated glycocalyx levels, endothelial dysfunction, edema, and inflammation in lungs during EVLP compared to both controls and heparin groups. High-doses of heparin demonstrated markedly increased perfusate syndecan-1 concentrations and deteriorated lung quality during EVLP compared with controls. Post-transplant graft function and inflammation were significantly improved in SF4-treated group compared to those in both control and heparin-treated groups.

CONCLUSION

This study demonstrated that HPSE activity inhibition by SF4 can improve graft preservation during EVLP by protecting the glycocalyx and endothelial function, leading to better lung function following transplantation.

Synthesis of Uronic Acid 1-Azasugars as Putative Inhibitors of α-Iduronidase, β-Glucuronidase and Heparanase

1-Azasugar analogues of l-iduronic acid (l-IdoA) and d-glucuronic acid (d-GlcA) and their corresponding enantiomers have been synthesized as potential pharmacological chaperones for mucopolysaccharidosis I (MPS I), a lysosomal storage disease caused by mutations in the gene encoding α-iduronidase (IDUA). The compounds were efficiently synthesized in nine or ten steps from d- or l-arabinose, and the structures were confirmed by X-ray crystallographic analysis of key intermediates. All compounds were inactive against IDUA, although l-IdoA-configured 8 moderately inhibited β-glucuronidase (β-GLU). The d-GlcA-configured 9 was a potent inhibitor of β-GLU and a moderate inhibitor of the endo-β-glucuronidase heparanase. Co-crystallization of 9 with heparanase revealed that the endocyclic nitrogen of 9 forms close interactions with both the catalytic acid and catalytic nucleophile.

Antioxidant and Immunostimulatory Activities of a Submerged Culture of Cordyceps sinensis Using Spent Coffee

Spent coffee grounds (SCG) are inexpensive materials that have been used as a source of antioxidants and polysaccharides with immunostimulatory activity. In this study, we performed a microbial fermentation of SCG using Cordyceps sinensis and investigated the radical scavenging and immunostimulatory activity of fermented SCG. SCG fermentation using C. sinensis was performed at 25 °C for 8 d. The polyphenol content of the fermented SCG increased from 1022.4 to 1562.0 μg/mL. The glucosamine content of the mycelia also continuously increased during fermentation. The main polyphenol compounds of fermented SCG were chlorogenic acid and p-coumaric acid, which were increased by fermentation. Fermented SCG also showed significantly higher content of chlorogenic acid isomers than unfermented SCG. The fermented SCG exhibited significantly higher 2,2-diphenyl-2-picrylhydrazyl hydrate (half maximal inhibitory concentration: IC₅₀, 0.37 mg/mL) and 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (IC₅₀, 0.93 mg/mL) radical scavenging activities than those of the control (0.54 mg/mL and 1.20 mg/mL, respectively; p < 0.05). The fermented SCG stimulated macrophages and promoted the production of various immunostimulatory cytokines (IL-12, IL-6, and TNF-α) compared to control; therefore, microbial fermentation of SCG using C. sinensis is an effective means of generating antioxidant and immunostimulatory materials.

Imine Amidation Catalyzed by a Chiral VAPOL Calcium Phosphate

Over the last 16 years, chiral phosphoric acids (CPAs) have been shown to be excellent asymmetric catalysts, very effectively used in constructing chiral molecules with high enantiocontrol. In 2010, Ishihara et al. discovered that chiral metal phosphate complexes (or salts) could be found in substantial quantities, as contaminates, in some reported CPA-catalyzed reactions (Hatano, M.; Moriyama, K.; Maki, T.; Ishihara, K. Angew. Chem., Int. Ed. 2010, 49, 3823-3826). These metal phosphates were shown to actually catalyze the reactions in addition to CPAs. In this work, we have investigated in depth a reaction first reported to be catalyzed by CPAs based on a vaulted bis-phenanthrol (VAPOL) backbone. We have found that VAPOL metal phosphates were, in fact, superior catalysts for this reaction. Upon optimization, a wide substrate scope, low catalyst loading, and mild conditions could provide intermolecular imine amidation reactions producing chiral N,N'-aminal products in high yields and with excellent ee values (up to >99% yield, >99% ee).

Heparanase is Involved in Leukocyte Migration

Leukocyte migration is essential for exerting self-defense mechanisms. During the extravasation process, leukocytes transmigrate through the endothelial lining and the subendothelial basement membrane. Accumulating evidence supports the involvement of heparanase in this process. Altered cellular distribution resulting in relocalization of heparanase to the leading edge of migration is a key event to rapidly turn on the function of the enzyme during migration. This review presents current research investigating the cellular machinery that builds up a functional subcellular structure for leukocyte attachment to and degradation of the extracellular matrix. Recent advances in the understanding of the roles of heparanase in inflammatory diseases and pharmacological approaches to control heparanase-mediated actions during inflammation are also discussed.

Iron-catalyzed C–O bond functionalization of butyrolactam derivatives with various N-/C-nucleophiles

An iron-catalyzed C–O bond functionalization of butyrolactam derivatives with N-/C-nucleophiles to enable the synthesis of butyrolactam derivatives has been developed.

Selective trihydroxylated azepane inhibitors of NagZ, a glycosidase involved in Pseudomonas aeruginosa resistance to β-lactam antibiotics

The synthesis of a series of d-gluco-like configured 4,5,6-trihydroxyazepanes bearing a triazole, a sulfonamide or a fluorinated acetamide moiety at C-3 is described. These synthetic derivatives have been tested for their ability to selectively inhibit the muropeptide recycling glucosaminidase NagZ and to thereby increase sensitivity of Pseudomonas aeruginosa to β-lactams, a pathway with substantial therapeutic potential. While introduction of triazole and sulfamide groups failed to lead to glucosaminidase inhibitors, the NHCOCF₃ analog proved to be a selective inhibitor of NagZ over other glucosaminidases including human O-GlcNAcase and lysosomal hexosaminidases HexA and B.

Stereoselective annulation between an allene, an alkene, and two nitrosoarenes to access bis(isoxazoliodine) derivatives

This work reports metal-free annulations between one allene, two nitrosoarenes and one electron-deficient alkene to afford bis(isoxazolidine) derivatives stereoselectively. This process involves an initial formation of isoxazolidin-4-imine oxides, followed by their dipolar [3 + 2]-cycloaddition with electron-deficient alkenes. To highlight the utility, the annulations of 5-alleneyl-1-enes with nitrosoarenes were also feasible to afford the desired bis(isoxazolidine) products with excellent stereocontrol. The resulting bis(isoxazolidine) products produced from two systems were reduced with Zn/MeOH to induce reductive N-O cleavages, yielding branched polyaminols stereoselectively.

Regioselective 1,2-addition of allenamides with N-haloimides: synthesis of 2-halo allylic aminal derivatives

A strategy for the synthesis of 2-halo allylic aminal derivatives through regioselective 1,2-addition of allenamides with N-haloimides is presented. This reaction was conducted under very mild conditions and gave up to 99% yield. Moreover, the obtained halides allow functional group diversification by palladium-catalyzed coupling reactions, which could act as potential intermediates for the synthesis of valuable compounds.

Microbial metabolites and derivatives targeted at inflammation and bone diseases therapy: chemistry, biological activity and pharmacology

Microbial metabolites have attracted increasing interest as a source of therapeutics and as probes for biological mechanisms. New microbial metabolites and derivatives targeted at inflammation and bone disease therapy have been identified by focusing on prostaglandin release, osteoblast differentiation and immune cell functions. These modulators of inflammatory processes and bone disease contribute to our understanding of biological mechanisms and support identification of the therapeutic potential of drug lead candidates. The present review describes recent advances in the chemistry and analysis of inhibitors of prostaglandin release or other functional molecules of immune cells, as well as inducers of osteoblast differentiation, including biological and pharmacological activities.The Journal of Antibiotics advance online publication, 1 November 2017; doi:10.1038/ja.2017.138.

Heparanase: a rainbow pharmacological target associated to multiple pathologies including rare diseases

In recent years, heparanase has attracted considerable attention as a promising target for innovative pharmacological applications. Heparanase is a multifaceted protein endowed with enzymatic activity, as an endo-β-D-glucuronidase, and nonenzymatic functions. It is responsible for the cleavage of heparan sulfate side chains of proteoglycans, resulting in structural alterations of the extracellular matrix. Heparanase appears to be involved in major human diseases, from the most studied tumors to chronic inflammation, diabetic nephropathy, bone osteolysis, thrombosis and atherosclerosis, in addition to more recent investigation in various rare diseases. The present review provides an overview on heparanase, its biological role, inhibitors and possible clinical applications, covering the latest findings in these areas.

An iminosugar-based heparanase inhibitor heparastatin (SF4) suppresses infiltration of neutrophils and monocytes into inflamed dorsal air pouches

Local infiltration of inflammatory cells is regulated by a number of biological steps during which the cells likely penetrate through subendothelial basement membranes that contain heparan sulfate proteoglycans. In the present study, we examined whether administration of heparastatin (SF4), an iminosugar-based inhibitor of heparanase, could suppress local inflammation and degradation of heparan sulfate proteoglycans in basement membranes. In a carrageenan- or formyl peptide-induced dorsal air pouch inflammation model, the number of infiltrated neutrophils and monocytes was significantly lower in mice after topical administration of heparastatin (SF4). The concentration of chemokines MIP-2 and KC in pouch exudates of drug-treated mice was similar to control. In a zymosan-induced peritonitis model, the number of infiltrated cells was not altered in drug-treated mice. To further test how heparastatin (SF4) influences transmigration of inflammatory neutrophils, its suppressive effect on migration and matrix degradation was examined in vitro. In the presence of heparastatin (SF4), the number of neutrophils that infiltrated across a Matrigel-coated polycarbonate membrane was significantly lower, while the number of neutrophils passing through an uncoated membrane was not altered. Lysate of bone marrow-derived neutrophils released sulfate-radiolabeled macromolecules from basement membrane-like extracellular matrix, which was suppressed by heparastatin (SF4). Heparan sulfate degradation activity was almost completely abolished after incubation of lysate with protein G-conjugated anti-heparanase monoclonal antibody, strongly suggesting that the activity was due to heparanase-mediated degradation. Taken together, in a dorsal air pouch inflammation model heparastatin (SF4) potentially suppresses extravasation of inflammatory cells by impairing the degradation of basement membrane heparan sulfate.

Heparanase augments inflammatory chemokine production from colorectal carcinoma cell lines

To explore possible roles of heparanase in cancer-host crosstalk, we examined whether heparanase influences expression of inflammatory chemokines in colorectal cancer cells. Murine colorectal carcinoma cells incubated with heparanase upregulated MCP-1, KC, and RANTES genes and released MCP-1 and KC proteins. Heparanase-dependent production of IL-8 was detected in two human colorectal carcinoma cell lines. Addition of a heparanase inhibitor Heparastatin (SF4) did not influence MCP-1 production, while both latent and mature forms of heparanase augmented MCP-1 release, suggesting that heparanase catalytic activity was dispensable for MCP-1 production. In contrast, addition of heparin to the medium suppressed MCP-1 release in a dose-dependent manner. Similarly, targeted suppression of Ext1 by RNAi significantly suppressed cell surface expression of heparan sulfate and MCP-1 production in colon 26 cells. Taken together, it is concluded that colon 26 cells transduce the heparanase-mediated signal through heparan sulfate binding. We propose a novel function for heparanase independent of its endoglycosidase activity, namely as a stimulant for chemokine production.

Involvement of heparanase in migration of microglial cells

Heparanase, a matrix-degrading enzyme that cleaves heparan sulfate side chains from heparan sulfate proteoglycans (HSPGs), has been shown to facilitate cell invasion, migration, and extravasation of metastatic tumor cells or immune cells. In this study, the expression and functions of heparanase were investigated using rat primary cultured microglia, the resident macrophages in the brain. The microglia were found to express heparanase mRNA and protein. Microglia treated with lipopolysaccharide (LPS) were activated, expressed induced nitric oxide synthase and elevated the expression of heparanase. Heparanase has two molecular weights: a 65 kDa latent form and an active 50 kDa. Both forms were expressed by LPS-treated activated microglia; however, untreated microglia primarily expressed the latent form. Cell lysates from microglia actually degraded Matrigel containing HSPG. Heparanase was colocalized with the actin cytoskeleton in microglial leading edges or ruffled membranes. Microglia transmigrated through a Matrigel-coated pored membrane. This process was inhibited by SF-4, a specific heparanase inhibitor, in a concentration-dependent manner. Degraded HSPG was generated when microglia transmigrated through the coated membrane, and this was also inhibited by SF-4. The results suggest the involvement of heparanase in the migration or invasion of microglia or brain macrophages across basement membrane around brain vasculature.

Synthesis of substituted septanosyl-1,2,3-triazoles

A carbohydrate-based oxepine, derived from 2-deoxy-D-arabino-hexopyranose, was used to prepare a family of septanosyl-1,2,3-triazoles in four steps. DMDO mediated epoxidation of the oxepine followed by trapping of the intermediate 1,2-anhydroseptanose by sodium azide gave the beta-substituted glycosyl azide. The septanosyl azide was then reacted with a number of alkynes under thermal Huisgen or copper(I) mediated reaction conditions. Hydrogenolysis of benzyl protecting groups gave substituted septanosyl-1,2,3-triazoles. The new septanose-based structures were then evaluated as potential glycosidase inhibitors.

Heparanase regulates esophageal keratinocyte differentiation through nuclear translocation and heparan sulfate cleavage

Heparanase is an endo-beta-glucuronidase that specifically cleaves heparan sulfate (HS) chains. Heparanase is involved in the process of metastasis and angiogenesis through the degradation of HS chains of the extracellular matrix and cell surface. Recently, we demonstrated that heparanase was localized in the cell nucleus of normal esophageal epithelium and esophageal cancer, and that its expression was correlated with cell differentiation. However, the nuclear function of heparanase remains unknown. To elucidate the role of heparanase in esophageal epithelial differentiation, primary human esophageal cells were grown in monolayer as well as organotypic cultures, and cell differentiation was induced. Expression of heparanase, HS, involucrin, and p27 was determined by immunostaining and Western blotting. SF4, a novel pharmacological inhibitor, was used to specifically inhibit heparanase activity. Upon esophageal cell differentiation, heparanase was translocated from the cytoplasm to the nucleus. Such translocation of heparanase appeared to be associated with the degradation of HS chains in the nucleus and changes in the expression of keratinocyte differentiation markers such as p27 and involucrin, whose induction was inhibited by SF4. Furthermore, these in vitro observations agreed with the expression pattern of heparanase, HS, involucrin, cytokeratin 13, and p27 in normal esophageal epithelium. Nuclear translocation of heparanase and its catalytic cleavage of HS may play a critical role in the differentiation of esophageal epithelial cells. Our study provides a novel insight into the role of heparanase in an essential differentiation process.

1-[4-(1H-Benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea derivatives as small molecule heparanase inhibitors

A novel class of 1-[4-(1H-benzoimidazol-2-yl)-phenyl]-3-[4-(1H-benzoimidazol-2-yl)-phenyl]-ureas are described as potent inhibitors of heparanase. Among them are 1,3-bis-[4-(1H-benzoimidazol-2-yl)-phenyl]-urea (7a) and 1,3-bis-[4-(5,6-dimethyl-1H-benzoimidazol-2-yl)-phenyl]-urea (7d), which displayed good heparanase inhibitory activity (IC(50) 0.075-0.27 microM). Compound 7a showed good efficacy in a B16 metastasis model.

Synthesis and biological evaluation of gem-diamine 1-N-iminosugars related to L-iduronic acid as inhibitors of heparan sulfate 2-O-sulfotransferase

A variety of gem-diamine 1-N-iminosugars related to L-iduronic acid were synthesized and evaluated as inhibitors of heparan sulfate uronyl 2-O-sulfotransferase using an in vitro enzyme assay. Two iminosugars containing guanidino groups acted as potent in vitro inhibitors of the enzyme.

Brønsted Acid-Catalyzed Imine Amidation

A new method for the Brønsted acid-catalyzed addition of amide nucleophiles to imines to produce protected aminal products is described. Simple Brønsted acids (phenyl phosphinic acid and trifluoromethanesulfonimide) were shown to be excellent catalysts, providing high yields of the aminal product. A catalytic asymmetric imine amidation using sulfonamides as nucleophiles was successful when a hindered biaryl phosphoric acid catalyst derived from 2,2'-diphenyl-[3,3'-biphenanthrene]-4,4'-diol (VAPOL) was used. Excellent yields and enantioselectivities were found in these additions (up to 99% ee).

N-(4-{[4-(1H-Benzoimidazol-2-yl)-arylamino]-methyl}-phenyl)-benzamide derivatives as small molecule heparanase inhibitors

A novel class of N-(4-{[4-(1H-benzoimidazol-2-yl)-arylamino]-methyl}-phenyl)-benzamides are described as inhibitors of the endo-beta-glucuronidase heparanase. Among them are N-(4-{[4-(1H-benzoimidazol-2-yl)-phenylamino]-methyl}-phenyl)-3-bromo-4-methoxy-benzamide (15h), and N-(4-{[5-(1H-benzoimidazol-2-yl)-pyridin-2-ylamino]-methyl}- phenyl)-3-bromo-4-methoxy-benzamide (23) which displayed good heparanase inhibitory activity (IC(50) 0.23-0.29 microM), with the latter showing oral exposure in mice.

2,3-Dihydro-1,3-dioxo-1H-isoindole-5-carboxylic acid derivatives: a novel class of small molecule heparanase inhibitors

A novel class of 2,3-dihydro-1,3-dioxo-1H-isoindole-5-carboxylic acids are described as inhibitors of the endo-beta-glucuronidase heparanase. Several of the compounds, for example, 2-[4-propylamino-5-[5-(4-chloro)phenyl-benzoxazol-2-yl]phenyl]-2,3-dihydro-1,3-dioxo-1H-isoindole-5-carboxylic acid (9c), display potent heparanase inhibitory activity (IC(50) 200-500 nM) and have high selectivity (>100-fold) over human beta-glucuronidase. They also show anti-angiogenic effects. Such compounds should serve as useful biological tools and may provide a basis for the design of novel therapeutic agents.

Synthesis and evaluation of the glycosidase inhibitory activity of 5-hydroxy substituted isofagomine analogues

An efficient strategy for the synthesis of 5-hydroxy substituted isofagomine analogues and , having both -CH2OH/CH3 and -OH functionality at the C-5 position, and evaluation of their inhibitory potency is reported. The synthetic methodology involves the aldol-Cannizzaro reaction of easily available alpha-d-xylopentodialdose followed by hydrogenolysis to afford the triol . Selective amidation of the alpha- and beta-hydroxymethyl group at C-4, deprotection of the 1,2-acetonide group and hydrogenation gave the target molecules, which were found to be potent against beta-glycosidases with IC50 values in the micro molar range. Compound showed excellent potency against glycosidases and human salivary amylase.

Heparanase expression correlates with malignant potential in human colon cancer

PURPOSE

Heparanase cleaves carbohydrate chains of heparan sulphate proteoglycans and is an important component of the extracellular matrix. This study was designed to determine the relation between heparanase expression and prognosis of patients with colon cancer.

METHODS

The study included 54 patients (35 males and 19 females) who underwent colorectal resection for colorectal cancer between January 1992 and December 1994. Expression of heparanase protein and mRNA were determined and correlated with various clinicopathological parameters. In vitro studies were also performed to examine tumor invasion and to test the effects of heparanase inhibition, and in vivo studies were performed to examine tumor metastasis and prognosis.

RESULTS

Heparanase expression was detected in the invasion front of the tumor in 37 of 54 (69%) colon cancer samples, whereas 17 of 54 (31%) tumors were negative. Expression of heparanase was significantly more frequent in tumors of higher TNM stage (P=0.0481), higher Dukes stage (P=0.0411), higher vascular infiltration (P=0.0146), and higher lymph vessel infiltration (P=0.0010). Heparanase expression in colon cancers correlated significantly with poor survival (P=0.0361). Heparanase-transfected colon cancer cells exhibited significant invasion compared with control-transfected colon cancer cells (P=0.001), and the peritoneal dissemination model also showed the malignant potential of heparanase-transfected cells, as assayed by number of nodules (P=0.017) and survival (P=0.0062). Inhibition of heparanase significantly reduced the invasive capacity of cancer cells (P=0.003).

CONCLUSIONS

Heparanase is a marker for poor prognosis of patients with colon cancer and could be a suitable target for antitumor therapy in colon cancer.

Structure-based design of a selective heparanase inhibitor as an antimetastatic agent

Heparanase is an endo-β-d-glucuronidase that degrades heparan sulfate glycosaminoglycans in the extracellular matrix and the basement membrane and is well known to be involved in tumor cell invasion and angiogenesis. We have focused on heparanase as a target for antitumor agents, especially antimetastatic agents. (R)-3-hexadecanoyl-5-hydroxymethyltetronic acid (RK-682) was found to display an inhibitory activity against heparanase in our screening of natural sources. Because RK-682 has been reported to show inhibitory activities against several enzymes, we have tried to develop selective heparanase inhibitors using the method of rational drug design. Based on the structure of the heparanase/RK-682 complex, we speculated that selective inhibitory activity against heparanase could be acquired by arylalkylation, namely, by benzylation of the 4-position of RK-682. Among the rationally designed 4-alkyl-RK-682 derivatives, 4-benzyl-RK-682 has been found to possess a selective inhibitory activity for heparanase (IC50 for heparanase, 17 μmol/L; IC50 for other enzymes, &gt;100 μmol/L). 4-Benzyl-RK-682 also inhibited the invasion and migration of human fibrosarcoma HT1080 cells (IC50 for invasion, 1.5 μmol/L; IC50 for migration, 3.0 μmol/L). On the other hand, RK-682 had no inhibitory effect on the invasion and migration of HT1080 cells at doses of up to 100 μmol/L.

Heparanase as a molecular target of cancer chemotherapy

Cancer cells require the ability to degrade the extracellular matrix (ECM) in order to turn into invasive and metastatic cancer cells. Many proteases and glycosidases are essential in the process of dissolving the components of the ECM. An endo-beta-D-glucuronidase, heparanase, is capable of specifically degrading one of the ECM components, heparan sulfate, and this activity is associated with the metastatic potential of tumor cells. Since heparanase mRNA is overexpressed in many human tumors (e.g., hepatomas, head and neck tumors, and esophageal carcinomas), the mechanisms regulating the activity of heparanase should be clarified; considering the possible role of heparanase in cancer, the development of heparanase inhibitors would appear to be advantageous. This review will focus on recent findings that have contributed to the characterization of heparanase and to the elucidation of the transcriptional regulation of heparanase mRNA expression, as well as the development of heparanase inhibitors.

Synthesis of protected 2-amino-2-deoxy-D-xylothionolactam derivatives and some aspects of their reactivity

The synthesis of polyfunctionalized delta-lactams as key intermediates of glycomimetics in the 2-acetamido-2-deoxy sugar series is presented. Starting from a chiral gamma-amino vinylic ester synthesized from Garner's aldehyde and after regioselective reduction, 1-azido-3-(N-tert-butyloxycarbonyl-2,2-dimethyloxazolidin-4-yl)-2-propene was obtained. Next, a cis-dihydroxylation reaction provided the protected D-xylitol and L-arabinitol azides. A simple protection-deprotection sequence, followed by an oxidation and a reductive cyclization, led to protected 2-amino-delta-lactams bearing a tert-butyloxycarbonyl group on the amine functionality. To explore the reactivity of such compounds, activation of the lactam into the corresponding thionolactam was performed. The resulting 2-amino-D-xylothionolactam derivative, a versatile intermediate, allowed access to a first generation of protected 2-amino-D-xylosamidoxime derivatives which are of interest as precursors of N-acetylhexosaminidase and N-acetylglucosaminyltransferase inhibitors. In this series of compounds, epimerization at C-2 was observed. AM(1) calculations performed on these analogs showed that they adopted a B(2,5) conformation and that the axial epimer was favored in the protected series whereas the equatorial epimer was preferred in the unprotected series.

Synthesis of [(2S,3S,4R)-3,4-dihydroxypyrrolidin-2-yl]-5-methylfuran-4-carboxylic acid derivatives: new leads as selective beta-galactosidase inhibitors

The preparation of [(2S,3S,4R)-3,4-dihydroxypyrrolidin-2-yl]furan derivatives in a stereoselective route starting from D-glucose and ethyl acetoacetate is presented. Ethyl ester (6), N,N-diethylamide (7) and N-isopropylamide (8) have been tested towards 25 glycosidases. Ester (6) is a selective inhibitor of beta-galactosidases. The new compounds represent a new type of imino-C-nucleoside analogues.

N-alkyl-3-decarboxy-3-hydroxymethylsiastatin B, a new family of glycosidase inhibitors of gem-diamine 1-N-iminosugars

N-Alkyl-3-decarboxy-3-hydroxymethylsiastatin B, N-alkyl analogues of gem-diamine 1-N-iminosugars, is a new family of glycosidase inhibitors that have been synthesized from siastatin B isolated from Streptomyces culture. These compounds were evaluated as glycosidase inhibitors.

Beta-D-glycosylamidines: potent, selective, and easily accessible 1-glycosidase inhibitors

Beta-D-glycosylamidines, in which a glycon is connected via an N-glycoside linkage with a substituted amidine (aglycon), were synthesized in two steps from the corresponding sugars and served as stable and potent beta-glycosidase inhibitors with high selectivity according to the glycon- and alpha, beta-specificities of the enzymes.