Preparation of 5-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyloxy)-6-hydroxynap htho[2,3- f]quinoline-7,12-dione (FT-Alz), a new-type, potentially antitumor substance with various biological activities

The title compound (6), its structure being imaginatively created, has been prepared through coupling of alizarine blue (2), a classical dye, and 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl bromide (3). Compound 6 has considerably higher and different antitumor activity from that of doxorubicin or its analogue (10), and, further, has properties to reverse multidrug resistance (by P-glycoprotein), to inhibit topoisomerase II, and to induce apoptosis.

Total synthesis of both methyl 4a-carba-D-arabinofuranosides

[reaction: see text] The total synthesis of methyl 4a-carba-alpha-D-arabinofuranoside (1) and methyl 4a-carba-beta-D-arabinofuranoside (2) has been achieved starting from D-mannose (5). Key transformations included a ring-closing metathesis of diene 11 employing Schrock's catalyst followed by a stereoselective hydrogenation with Wilkinson's catalyst.

A total synthesis of the methyl glycoside of ganglioside GM(1)

The total synthesis of the methyl glycoside of GM(1) (1b) has been accomplished. The key step in the synthesis involves the sulfonamidoglycosidation reaction, which is used to create a beta-linkage leading to a GalNAc residue joined to the C4 hydroxyl group of a galactose unit of a C3 sialylated lactosyl moiety. The "proximal hydroxyl" directing effect, which has been postulated before, manifests in this context as well leading to the preponderant formation of the beta-glycoside. Together with asialo GM(1) and other substructures, the GM(1) methyl glycoside has been submitted for biological assays as potential ligands for bacterial and viral infection sites.

Synthesis, X-ray structure and high-resolution NMR spectroscopy of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside

The synthesis, crystal structure data and 1H and 13C NMR spectroscopy of methyl 3-azido-2,3-dideoxy-alpha-D-arabino-hexopyranoside (5b) is reported. This compound adopts the 4C1 conformation. Hydrogen-bonded molecules of 5b form helices around the crystallographic 4(1) axis.

Synthesis of 6,7-dideoxy-7-isothiocyanatoheptoses: stable fully unprotected monosaccharide isothiocyanates

Methyl 6,7-dideoxy-7-isothiocyanato-alpha-D-gluco (manno)(galacto)-heptopyranosides have been synthesized in four steps by homologation of the respective methyl hexopyranosides via the corresponding heptopyranosydurononitriles. Neither intra- nor intermolecular thiocarbamate formation was observed, even under rather strenuous acidic or basic conditions. The reducing derivative 6,7-dideoxy-7-isothiocyanato-alpha-D-gluco-heptopyranose was also a stable compound in aqueous solution in the absence of base. Formation of a six-membered intramolecular cyclic thiocarbamate was achieved in DMF solution in the presence of triethylamine. The title compounds are the first examples of stable fully unprotected monosaccharide isothiocyanates.

3,4-anhydro-1,2-O-isopropylidene-beta-D-tagatopyranose and 4,5-Anhydro-1,2-O-isopropylidene-beta-D-fructopyranose

3,4-Anhydro-1,2-O-isopropylidene-beta-D-tagatopyranose (8) and 4,5-anhydro-1,2-O-isopropylidene-beta-D-fructopyranose (10) have been prepared by treatment of 3,5-di-O-acetyl-1,2-O- isopropylidene-4-O-toluene-p-sulfonyl-beta-D-fructopyranose with methanolic sodium methoxide. The structures of 8 and 10 were assigned by 1H and 13C NMR spectroscopy and that of 10 by X-ray crystallography; both exist in half-chair conformations. Compounds 8 and 10 interconvert in aqueous sodium hydroxide, giving a ratio of 1:2 at equilibrium. The monoacetates of 8 and 10 (5-O-acetyl-3,4-anhydro-1,2-O-isopropylidene-beta-D-tagatopyranose and 3-O-acetyl-4,5-anhydro-1,2-O-isopropylidene-beta-D-fructopyranose) undergo stereospecific epoxide ring opening in 80% acetic acid to give mainly the axial monoacetates 5-O-acetyl-1,2-O-isopropylidene-beta-D-fructopyranose and 4-O-acetyl-1,2-O-isopropylidene-beta-D-tagatopyranose, respectively.

1,2-di-O-acetyl-5-O-benzoyl-3-deoxy-L-erythro-pentofuran ose, a convenient precursor for the stereospecific synthesis of nucleoside analogues with the unnatural beta-L-configuration

The title compound 1,2-di-O-acetyl-5-O-benzoyl-3-deoxy-L-erythro-pentofuranose (5), a useful precursor for the stereospecific synthesis of beta-L-nucleoside analogues as potential antiviral agents, has been synthesised by a multi-step reaction sequence from L-xylose with a 38% overall yield. The preparation involved conversion of L-xylose to 1,2-O-isopropylidene-alpha-L-xylofuranose which, upon selective 5-O-benzoylation and subsequent radical deoxygenation, provided the protected 3-deoxy sugar derivative. Finally, cleavage of the acetonide group gave the resulting 5-O-benzoyl-3-deoxy-L-erythro-pentose which was acetylated to afford crystalline alpha,beta-5.

Thermotropic and lyotropic properties of long chain alkyl glycopyranosides. Part I: monosaccharide headgroups

A systematic structure variation of a classical amphiphile (dodecyl-beta-D-glucopyranoside) is performed, demonstrating the influence of anomeric linkage, configuration, ring size and flexibility as well as electric charges on the mesophase behaviour. In addition, we have investigated the thermotropic and lyotropic properties of some long chain alkyl glycosides with monosaccharide headgroups. The thermotropism was measured with polarizing microscopy and differential scanning calorimetry, and additionally the lyotropism with FTIR spectroscopy and X-ray diffraction.

2-Deoxy-2-iodo- and 2-deoxy-2-bromo-alpha-glucopyranosyl trichloroacetimidates: highly reactive and stereoselective donors for the synthesis of 2-deoxy-beta-glycosides

[formula: see text] 2-Deoxy-2-iodo- and 2-deoxy-2-bromoglucopyranosyl trichloroacetimidates 8-10 and 22 are extremely useful precursors of 2-deoxy-beta-glycosides. These reactive glycosyl donors undergo highly stereoselective glycosidation reactions at -78 degrees C with a range of glycosyl acceptors using TBS-OTf as the activating agent. beta-Glycosides are obtained with > or = 19:1 selectivity in six of the seven examples reported herein.

2-Deoxy-2-iodo-alpha-mannopyranosyl and -talopyranosyl acetates: highly stereoselective glycosyl donors for the synthesis of 2-deoxy-alpha-glycosides

[formula: see text] TMS-OTf- or TBS-OTf-promoted glycosidation reactions of 2-deoxy-2-iodo-alpha-mannopyranosyl acetates 8-10 and the 2-deoxy-2-iodo-alpha-talopyranosyl acetate 11 provide the corresponding 2-deoxy-2-iodo-alpha-pyranosides, precursors to 2-deoxy-alpha-glycosides, as the only observed reaction products.

Chemoenzymatic synthesis and antitumor promoting activity of 6'- and 3-esters of 2-O-beta-D-glucosylglycerol

Through a simple chemoenzymatic approach 6'- and 3-esters of 2-O-beta-D-glucosylglycerol 1, with short-medium length fatty acid acyl chains, were prepared. The study of their in vitro antitumor promoting effect on Epstein-Barr virus early antigen (EBV-EA) activation, in comparison with that of the 1-esters previously described, confirms the significant activity of such monoacylated glycoglycerolipid analogues and establishes for the glucose series that the 1-substitution and the hexanoyl chain are the proper structural features for the maximum activity.

[Synthesis and biological activity of anomeric muramoyldipeptide butylglycosides]

The synthesis of anomeric butyl glycosides of muramyl dipeptide was reported. alpha-Butyl glycoside of N-acetyl-D-glucosamine was 4,6-O-benzylidenated and the benzylidene derivative was 3-O-alkylated by the Williamson reaction with sodium (S)-2-chloropropionate. The resulting protected alpha-butyl glycoside of muramic acid was then condensed with L-Ala-D-iGln-OBzl by the DCC-HOSu method. Mild acidic hydrolysis and subsequent catalytic hydrogenolysis of the resulting glycopeptide yielded the target alpha-butyl glycoside of N-acetyl-L-alanyl-D-isoglutamine. In the synthesis of beta-butyl glycoside of N-acetylmuramyl-L-alanyl-D-isoglutamine, 2-acetamido- 4,6-di-O-acetyl-2-deoxy-3-O-[(R)-1-(methoxycarbonyl)ethyl]-alpha- D-glucopyranose, a 1-OH derivative of muramic acid, was the key compound. Its interaction with the excess thionyl chloride resulted in the corresponding glycosyl halide, which was condensed with n-butanol according to Helferich. O-Deacetylation, 4,6-isopropylidenation, and subsequent alkaline hydrolysis of the resulting compound gave the protected beta-butyl glycoside of muramic acid. Its activation and condensation with L-Ala-D-iGln-OBzl and the subsequent removal of protective groups were performed in the same manner as the reactions in the synthesis of alpha-butyl glycoside of N-acetyl-L-alanyl-D-isoglutamine. The adjuvant activity of the butyl glycosides to HIV proteins rgp160 and rgp120 and their ability to affect in vitro HIV replication and the proliferation of mouse spleen T-cells were examined. The biological activity of anomeric muramyl dipeptides was shown to depend essentially on the configuration of their anomeric center.

Synthesis and use of glycosyl phosphates as glycosyl donors

Differentially protected glycosyl phosphates prepared by a straightforward synthesis from glycal precursors are used as powerful glycosyl donors. Activation of beta-glycosyl phosphates by TMSOTf at -78 degrees C achieves the selective formation of beta-glycosidic linkages in excellent yields with complete stereoselectivity. Reaction with thiols results in the conversion of glycosyl phosphates into thioglycosides in nearly quantitative yield. An orthogonal coupling strategy using glycosyl phosphate donors and thioethyl glycoside acceptors allows for the rapid synthesis of a trisaccharide.

Synthesis of the 3-methyl ether and 4-deoxy derivatives of 4-cyanophenyl 1,5-dithio-beta-D-xylopyranoside (Beciparcil)

Treatment of the 2,3-isopropylidene acetal of the title dithioxyloside with 2,4,5-triiodoimidazole-PPh3 caused replacement of the 4-hydroxyl group by iodine to afford 82% of the 4-axial iodide 6, converted by base into 4-cyanophenyl 2,3-O-isopropylidene-1,5-dithio-beta-D-glycero-pent-3-enopyranoside++ + (8). Acid treatment of 8 gave 87% of the deacetonated glycos-3-ulose, borohydride reduction of which afforded 63% of 4-cyanophenyl 4-deoxy-1,5-dithio-alpha-L-threo-pentopyranoside (3), together with 27% of the 3-axial epimer. The 3-methyl ether of the title dithioxyloside was satisfactorily prepared via 2,4-protection as the cyclic phenylboronate, methylation, and deprotection; alternative strategy via the 2,4-bis(triisopropylsilyl) ether was complicated because of silyl-group migration under methylation conditions.

Synthesis and characterization of a photoactivatable glycoaryldiazirine for surface glycoengineering

Biological systems make considerable use of specific molecular interactions. Many biomolecules involved in biorecognition are glycosylated, the carbohydrate moiety playing an essential role. Controlled surface glycoengineering is thus of crucial importance in biosensing, cell guidance, and biomedical applications. This study describes the synthesis of an aryldiazirine-derivatized galactose and the functionalization of surfaces by carbohydrates using photochemical immobilization techniques. A photoactivatable glycosylated reagent was synthesized by addition of thiogalactopyranose to the maleimide group of N-[m-[3-(trifluoromethyl)diazirin-3-yl]phenyl]-4-maleimidobutyr amide (MAD) to give N-[m-[3-(trifluoromethyl)diazirin-3-yl]phenyl]-4-[3-thio (1-D-galactopyranosyl)succinimidyl]butyramide (MAD-Gal). The structure of the newly synthesized molecule was confirmed by UV spectroscopy, photoactivation, 1H NMR, and 13C NMR. MAD-Gal was immobilized on thin diamond films by photoactivation of the diazirine function (350 nm). Surface modification was investigated by XPS (X-ray photoelectron spectroscopy) and ToF-SIMS (time-of-flight secondary ion mass spectrometry). Imaging ToF-SIMS was applied to detect glycopatterns generated by mask-assisted lithography.

Synthesis of sulfated oligosaccharide glycosides having high anti-HIV activity and the relationship between activity and chemical structure

Sulfated laminara-oligosaccharide glycosides having high anti-human immunodeficiency virus (HIV) activities were synthesized from laminara-tetraose, -pentaose and -hexaose. The oligosaccharide glycosides were synthesized by treating peracetylated beta-oligosaccharides with various alcohols and Lewis acid catalysts. The effects of the number of glucose residues and the alkyl chain-length on anti-HIV activity were examined. The anti-HIV activity of sulfated dodecyl laminara-pentaosides and -hexaosides increased with increasing degree of sulfation (DS) and the pentaoside having an almost fully-sulfated saccharide portion had the highest activity, whereas for the hexaoside a somewhat lower DS manifested the highest activity. Sulfated laminara-oligosaccharide glycosides having fluoroalkyl-containing aglycons of high hydrophobicity showed potent inhibitory effects against HIV infection. In contrast, hydrophilic substituents containing oligo(ethyleneoxy) groups as aglycons in the sulfated oligosaccharides did not show high anti-HIV activity.

[Synthesis of Neu5Ac(alpha2-->6)[Gal(alpha1-->3)]GalNAcalpha and Neu5Ac(alpha2-->6)[Gal(beta1-->3)]GalNAcalpha trisaccharides as protected trifluoroacetamidopropyl glycosides]

Protected sialo-containing trisaccharides, fragments of oligosaccharide chains of mucin glycoproteins, were synthesized. Regioselective sialylation of the primary hydroxyl group of (3-fluoroacetamidopropyl)-2-azido-2-deoxy-3-O-(2,3,4,6-tetra-O-ben zyl)-alpha -D-galactopyranosyl)-alpha-D-galactopyranoside with methyl ester of peracetyl-beta-ethylthioglycoside of N-acetylneuraminic acid in the presence of N-iodosuccinimide and trifluoromethanesulfonic acid (or its trimethylsilyl ester) yielded 39 and 25% of alpha- and beta-sialyl-(2-->6)biosides, respectively. Catalytic hydrogenolysis of the azide and benzyl groups of the alpha-anomer followed by N- and O-acetylation gave target trifluoroacetamidopropyl glycoside, Neu5Ac(alpha 2-->6)[Gal(alpha 1-->3)]GalNAc alpha-OSp, as a peracetate. An analogous coupling of the sialyl donor with (3-fluoroacetamidopropyl)-2-acetamido-2-deoxy-3-O- (2,3,4,6-tetra-O-acetyl)-beta-D-galactopyranosyl)-alpha-D-galactopyranos ide affords acetylated trifluoroacetamidopropyl glycoside Neu5Ac(alpha 2-->6)[Gal(beta 1-->3)]GalNAc alpha-OSp in a yield of 15% and the corresponding Neu5Ac(beta 2-->6)-anomer in a yield of 12%. After O-deacetylation and N-detrifluoroacetylation, these sialylbiosides can be used as ligands in preparing neoglycoconjugates.

Synthesis and antitumor activity of new glycosides of epipodophyllotoxin, analogues of etoposide, and NK 611

A series of 3-amino- and 3-alkylamino-2-deoxy-beta-D-ribo- and beta-D-arabino-glycosides of 4'-demethylepipodophyllotoxin have been synthesized by means of an improved trimethylsilyliodide procedure for the podophyllotoxin-4'-demethylepipodophyllotoxin conversion, an efficient and high yielding synthesis of silyl glycoside donors of 3-azido-2,3-dideoxy-beta-D-ribo- and beta-D-arabino-hexopyranosides and stereoselective glycosylations. In vitro evaluation of cytotoxic effects against murine L1210 leukemia critically demonstrates the essential role played by a 4,6-acetal for biological activity. Among the most cytotoxic compounds, 3-amino-2,3-dideoxy- and 3-N, N-(dimethylamino)-2,3-dideoxy etoposide analogues, 17 and 27-29 are at least as potent as etoposide on the in vivo P388 (iv/ip) murine leukemia models. However, surprisingly enough, none of these compounds inhibits the human DNA topoisomerases I or II or binds to tubulin to prevent its polymerization and microtubule assembly. Therefore, their mechanism of action remains to be cleared up.

Quanolirones I and II, two new human cytomegalovirus protease inhibitors produced by Streptomyces sp. WC76535

Two new naphthacenequinone glycosides, quanolirones I (1) and II (2) were isolated, together with the known compound galtamycin from the fermentation broth of Streptomyces sp. WC76535. The structures 1 and 2 were established by analysis of their spectroscopic data and by comparison of their data to those of galtamycin. Compounds 1, 2, and galtamycin showed inhibitory activity against HCMV protease with IC50 values of 14, 35, and 52 microM, respectively.

Synthesis of 4-cyanophenyl and 4-nitrophenyl 1,5-dithio-L- and -D-arabinopyranosides possessing antithrombotic activity

5-S-Benzoyl-2,3-O-isopropylidene-5-thio-L-arabinose, prepared from L-arabinose diethyl dithioacetal gave, on treatment with sodium methoxide in methanol, 4-O-benzoyl-2,3-O-isopropylidene-5-thio-L-arabinopyranose 12 which was converted into its 1-O-acetate 14. Hydrolysis of 12 in acetic acid-water afforded, after acetylation, 1,2,3-tri-O-acetyl-4-O-benzoyl-5-thio-L-arabinopyranose 17 which was transformed into 2,3-di-O-acetyl-4-O-benzoyl-5-thio-L-arabinopyranosyl bromide 20. Zemplén deacylation of 17 gave 5-thio-L-arabinopyranose which was converted via 1,2,3,4-tetra-O-acetyl-5-thio-beta-L-arabinopyranose 5 into 2,3,4-tri-O-acetyl-5-thio-beta-L-arabinopyranosyl bromide 6 and into O-(2,3,4-tri-O-acetyl-5-thio-L-arabinopyranosyl) trichloro-acetimidate 7. Glycosidation of 4-nitrophenol with 12 under the Mitsunobu conditions afforded 4-nitrophenyl 4-O-benzoyl-2,3-O-isopropylidene-5-thio-alpha- and beta-L-arabinopyranoside in a approximately 1:2 ratio. Condensation of the glycosyl donors 6, 7, 17, and 20 with 4-cyano- and 4-nitrobenzenethiol yielded, after deacylation, 4-cyano- and 4-nitrophenyl 1,5-dithio-alpha- and beta-L-arabinopyranosides 28 alpha, 28 beta, 29 alpha and 29 beta in different ratios and yields, depending on the reaction conditions applied. In a similar manner the corresponding D-isomers 30 alpha, 30 beta, 31 alpha and 31 beta were also prepared. All of these glycosides, except 28 alpha, showed a stronger oral antithrombotic effect in rats as compared to beciparcil, used as reference.

[Synthesis of oligosaccharides related to HNK-1 antigen. 2. Synthesis of 3'''-O-(3-O-sulfo-beta-D-glucuronopyranosyl)-lacto-N-neotetrao se beta-propylglycoside]

A derivative of allyl 3"-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-lactoside with a free OH group at C-4GlcNAc was glycosylated with trichloroacetimidate of selectively protected GlcA(beta 1-->3)Gal alpha disaccharide in dichloromethane in the presence of trimethylsilyl triflate resulting in a pentasaccharide product with an 82% yield. This product was converted to monohydroxy derivative with a free OH group at C-3GlcA via the formation and the subsequent opening of the 6,3-lactone ring in the glucuronic acid residue. The 3"'-O-sulfation of the monohydroxy derivative, the removal of the protective groups, and the reduction of the allyl aglycon yielded the pentasaccharide propyl glycoside NaSO3-3GlcA(beta 1-->3)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc beta-Opr comprising the oligosaccharide chain of the SGGL-1 glycolipid, which is recognized by HNK-1 antibodies. NaSO3-3GlcA(beta 1--> 3)Gal beta OAll, GlcA(beta 1-->3)Gal(beta 1-->4)GlcNAc(beta 1-->3)Gal(beta 1-->4)Glc beta-OPr and GlcA(beta 1-->3)Gal beta OAll were synthesized in a similar way.

Induction of KDNase Sm, a deaminoneuraminic acid (KDN) residue-specific sialidase from Sphingobacterium multivorum, using synthetic KDN-glycosides

Various aryl and alkyl alpha-glycosides of KDN were synthesized and tested as substrates for their susceptibility to a deaminoneuraminic acid (KDN)-specific sialidase from Sphingobacterium multivorum, designated KDNase Sm. The synthetic KDN-glycosides were all hydrolyzed by the action of KDNase Sm. A hydroxyl group at C-5 position of KDN was required for the recognition by the enzyme, and was shown not to be replaced by an amino- or an acylamino group for the enzymatic recognition. These synthetic KDN-glycosides were also examined for their inducing activity of KDNase in S. multivorum and were shown to induce the KDNase activity effectively when the bacterium was cultured minimum salt medium containing both 0.1% glucose and 0.1% various KDN-glycosides. No KDNase activity was induced by the KDN-glycosides without 0.1% glucose. This is the first case of using synthetic KDN-glycosides as inducers of KDNase Sm.

Studies on selectin blockers. 6. Discovery of homologous fucose sugar unit necessary for E-selectin binding

We describe a mimic of the sugar unit of the E-selectin ligand, sialyl Lewis X (sLeX). Carbohydrates are entering the realm of rational drug design, aided by the growing understanding of the structure-function relationships. We investigated a new methodology of preparing sLeX mimetics and developed a potent E-selectin blocker characterized by beta-turn dipeptides. Another characteristic point of this E-selectin blocker is that the six-membered fucose ring was replaced with a five-membered fucose ring. Interestingly, it was found that the five-membered fucose ring could also bind to a calcium ion on the E-selectin, which could be an important role of the six-membered fucose ring. Especially, the L-Ser-D-Glu and D-Ser-L-Glu derivatives 3a,b showed 65-90-fold more potent inhibitory activities than the sulfated LeX analogue 1. In addition, molecular dynamics (MD) studies indicated that the 2- and 3-OH groups of the six-membered fucose ring, which were necessary for the calcium binding, overlapped well with the 2- and 3-OH groups of the five-membered fucose ring. These new findings could be useful for the design of new types of selectin blockers.

The effects of glutathione glycoside in acetaminophen-induced liver cell necrosis

The hepatotoxic effects of high-dose acetaminophen (400 and 600 mg/kg body weight) were evaluated by determining the glutathione (GSH) and malondialdehyde (MDA) levels and the histological changes in the liver at 6 and 12 h, using C57BL/6J mice. Massive centrilobular hepatocyte necrosis associated with severe reduction of liver GSH and a significant increase in MDA levels were observed following acetaminophen intoxication. Administration of glutathione glycoside (GSH-glyc), a compound newly synthesized in our laboratory, 2 h after acetaminophen injection prevented changes in the GSH and MDA preserving their levels nearly to those of controls; in addition, histological evidence of hepatocyte necrosis was either abolished or severely reduced in the majority of animals. GSH-glyc is a nontoxic compound that can be used to transport GSH into cells, including those of brain and liver, and may prove to be useful for the prophylaxis and therapy of toxic tissue injury, including that induced by overdosage of acetaminophen.

Synthesis of hyaluronic-acid-related oligosaccharides and analogues, as their 4-methoxyphenyl glycosides, having N-acetyl-beta-D-glucosamine at the reducing end

To contribute to the possibilities to study the ability of oligosaccharide fragments of hyaluronic acid to induce angiogenesis, several hyaluronic-acid-related oligosaccharides and their 6-O-sulfated analogues were synthesised as their 4-methoxyphenyl glycosides having 2-acetamido-2-deoxy-D-glucopyranose at the reducing end. In all syntheses described, the D-glucopyranosyluronic acid residue was obtained by oxidation at C-6 of a corresponding D-glucopyranosyl residue after construction of the oligosaccharide backbone, using pyridinium dichromate and acetic anhydride.