Synthesis of regioselectively sulfated xylodextrins and crystal structure of sodium methyl β-d-xylopyranoside 4-O-sulfate hemihydrate

Methyl xylobioside and methyl xylotrioside were prepared from the peracetylated anomeric xylosyl trichloroacetimidates by reaction with methanol followed by Zemplén deacetylation. Methyl β-d-xylopyranoside, methyl β-d-xylobioside and methyl β-d-xylotrioside were subjected to treatment with dibutyltin oxide followed by reaction with the trimethylamine/sulfur trioxide complex in tetrahydrofuran. This way, preferential sulfation of the terminal 4-hydroxy group at the nonreducing xylopyranosyl unit was achieved. In addition, partial sulfation at position 2 of the distal xylose unit was observed. The substitution pattern was derived from NMR spectroscopic data and was confirmed by the X-ray structure determination of sodium methyl β-d-xylopyranoside 4-O-sulfate. The compound crystallized as a hemihydrate in a triclinic lattice of space group P1 and possesses a pseudomonoclinic 2D supramolecular structure. The sulfation of free pentose oligomers via their intermediate stannylene acetals may thus be exploited to generate biologically active oligosaccharides for biomedical applications.     

Deoxy and deoxyfluoro analogues of acetylated methyl beta-D-xylopyranoside--substrates for acetylxylan esterases

Four modified substrates for acetylxylan esterases, 2-deoxy, 3-deoxy, 2-deoxy-2-fluoro, and 3-deoxy-3-fluoro derivatives of di-O-acetylated methyl beta-D-xylopyranoside were synthesized via 2,3-anhydropentopyranoside precursors. Methyl 2,3-anhydro-4-O-benzyl-beta-D-ribopyranoside was transformed into methyl 2,3-anhydro-4-O-benzyl-beta-D-lyxopyranoside in three steps. The epoxide ring opening of 2,3-anhydropentopyranosides was accomplished either by hydride reduction or hydrofluorination. Methyl beta-D-xylopyranoside 2,3,4-tri-O-, 2,4-di-O-, and 3,4-di-O-acetates, and the prepared diacetate analogues were tested as substrates of acetylxylan esterases from Schizophyllum commune and Trichoderma reesei. Measurement of their rate of deacetylation pointed to unique structural requirements of the enzymes for the substrates. The enzymes differed particularly in the requirement for the trans vicinal hydroxy group in the deacetylation at C-2 and C-3 and in the tolerance to the presence of trans vicinal acetyl groups esterifying the OH group at C-2 and C-3.     

Synthesis of beta-D-GlcA-(1----3)-beta-D-Gal disaccharides with 4- and 6-sulfate groups and 4,6-disulfate groups.

The sodium salts of the 6-sulfate 7, the 4-sulfate 10, and the 4,6-disulfate 12 of benzyl 3-O-(beta-D-glucopyranosyl uronate)-beta-D-galactopyranoside (5) have been synthesized. Methyl (2,3,4-tri-O-acetyl-1-bromo-1-deoxy-alpha-d-glucopyran)uronate (1) was coupled with benzyl 2-O-benzoyl-4,6-O-benzylidene-beta-D-galactopyranoside (2) to yield 3. The benzylidene acetal of 3 was hydrolyzed to give benzyl 2-O-benzoyl-3-O-[methyl (2,3,4-tri-O-acetyl-beta-D-glucopyranosyl)uronate]-beta-D-galactopyra noside (4). Compound 4 was utilized as a key intermediate to prepare the sulfated disaccharides 7,10, and 12. Direct sulfation of 4 with sulfur trioxide-trimethylamine for 2 days yielded the 6-sulfate 6. The 4,6-disulfate 11 was accessible by running the reaction under the same conditions for 14 days. The 4-sulfate 9 was obtained after protecting the 6-OH group of 4 by reaction with benzoyl imidazole to give the 6-benzoate 8, followed by sulfation under vigorous conditions. Treatment of the protected compounds 4, 6, 9, and 11 with aqueous sodium hydroxide in tetrahydrofuran gave the unprotected 5, 7, 10, and 12, respectively.     

Mode of action of acetylxylan esterase from Streptomyces lividans: a study with deoxy and deoxy-fluoro analogues of acetylated methyl beta-D-xylopyranoside

Streptomyces lividans acetylxylan esterase removes the 2- or 3-O-acetyl groups from methyl 2,4-di-O-acetyl- and 3,4-di-O-acetyl beta-D-xylopyranoside. When the free hydroxyl group was replaced with a hydrogen or fluorine, the rate of deacetylation was markedly reduced, but regioselectivity was not affected. The regioselectivity of deacetylation was found to be independent of the prevailing conformation of the substrates in solution as determined by 1H-NMR spectroscopy. These observations confirm the importance of the vicinal hydroxyl group and are consistent with our earlier hypothesis that the deacetylation of positions 2 and 3 may involve a common ortho-ester intermediate. Another possible role of the free vicinal hydroxyl group could be the activation of the acyl leaving group in the deacetylation mechanism. Involvement of the free hydroxyl group in the enzyme-substrate binding is not supported by the results of inhibition experiments in which methyl 2,4-di-O-acetyl beta-D-xylopyranoside was used as substrate and its analogues or methyl beta-D-xylopyranoside as inhibitors. The enzyme requires for its efficient action the trans arrangement of the free and acetylated hydroxyl groups at positions 2 and 3.     

Transacetylations to carbohydrates catalyzed by acetylxylan esterase in the presence of organic solvent

Various conditions were applied to test the ability of acetylxylan esterase (AcXE) from Schizophyllum commune to catalyze acetyl group transfer to methyl beta-D-xylopyranoside (Me-beta-Xylp) and other carbohydrates. The best performance of the enzyme was observed in an n-hexane-vinyl acetate-sodium dioctylsulfosuccinate (DOSS)-water microemulsion at a molar water-detergent ratio (w(0)) of about 4-5. Although the enzyme was found to have a half-life of about 1 h in the system, more than 60% conversion of Me-beta-Xylp to acetylated derivatives was achieved. Under identical reaction conditions, the enzyme acetylated other carbohydrates such as methyl beta-D-cellobioside (Me-beta-Cel), cellotetraose, methyl beta-D-glucopyranoside (Me-beta-Glcp), 2-deoxy-D-glucose, D-mannose, beta-1,4-mannobiose, -mannopentaose, -mannohexaose, beta-1,4-xylobiose and -xylopentaose. This work is the first example of reverse reactions by an acetylxylan esterase and a carbohydrate esterase belonging to family 1.     

Synthesis of 2-hydroxyestriol monoglucuronides and monosulfates

The ring A monoglucuronides and monosulfates of 2-hydroxyestriol were synthesized from 2-hydroxyestriol 16,17-diacetate by means of the Koenigs-Knorr reaction with methyl alpha-acetobromoglucuronate and sulfation with sulfur trioxide-pyridine complex, respectively. The conjugated positions of these compounds were definitely established by conversion to 2-hydroxyestriol monomethyl ethers by methylation, then enzymatic hydrolysis. The ring D monoglucuronides and monosulfates of 2-hydroxyestriol were also prepared from 2-hydroxyestriol 2,3-dibenzyl ether by glucuronidation and sulfation in a similar fashion followed by debenzylation, respectively. The positions of conjugation were established on the basis of their 1H-nuclear magnetic resonance spectral data.     

Crystal and molecular structure of methyl L-glycero-α-D-manno-heptopyranoside, and synthesis of 1→7 linked L-glycero-D-manno-heptobiose and its methyl α-glycoside

Methyl l-glycero-α-d-manno-heptopyranoside was synthesized in good yield by a Fischer-type glycosylation of the heptopyranose with methanol in the presence of cation-exchange resin under reflux and microwave conditions, respectively. The compound crystallized from 2-propanol in an orthorhombic lattice of space group P2(1)2(1)2 showing a comparatively porous structure with a 2-dimensional O-H?O hydrogen bond network. As model compounds for the side chain domains of the inner core structure of bacterial lipopolysaccharide, l-glycero-α-d-manno-heptopyranosyl-(1→7)-l-glycero-d-manno-heptopyranose and the corresponding disaccharide methyl α-glycoside were prepared. The former compound was generated via glycosylation of a benzyl 5,6-dideoxy-hept-5-enofuranoside intermediate followed by catalytic osmylation and deprotection. The latter disaccharide was efficiently synthesized in good yield by a straightforward coupling of an acetylated N-phenyltrifluoroacetimidate heptopyranosyl donor to a methyl 2,3,4,6-tetra-O-acetyl heptopyranoside acceptor derivative followed by Zemplén deacetylation.     

Photoinduced electron transfer and chemical alpha-deoxygenation of D-galactono-1,4-lactone. Synthesis of 2-deoxy-D-lyxo-hexofuranosides

Two simple procedures for the synthesis of 2-deoxy-D-lyxo-hexono-1,4-lactone are described. Reductive cleavage of a 2-O-tosyl derivative of D-galactono-1,4-lactone in the presence of sodium iodide afforded the 2-deoxy derivative. On the other hand, alpha-deoxygenation of D-galactono-1,4-lactone was easily achieved by photochemical electron transfer deoxygenation of HO-2 as the 3-(trifluoromethyl)benzoate. Methyl 2-deoxy-beta-D-lyxo-hexafuranoside ('methyl 2-deoxy-beta-D-galactofuranoside') was synthesized and tested as substrate for exo beta-D-galactofuranosidase from Penicillium fellutanum. The reaction was followed by HPAEC, showing that methyl 2-deoxy-beta-D-galactofuranoside was not hydrolyzed by incubation with the enzyme. Neither the 2-deoxy lactone, nor the 2-deoxy-beta-D-galactofuranoside acted as inhibitors of the reaction with the 4-nitrophenyl beta-D-galactofuranoside. The present and our previous results show that the hydroxyl groups at C-2, C-3 and C-6 of the galactofuranoside are essential for interaction with the exo beta-D-galactofuranosidase.     

Characterisation and X-ray crystallography of products from the Bucherer-Bergs reaction of methyl 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside

Methyl 2,3-O-isopropylidene-alpha-D-mannofuranosidurononitrile [alternative name: methyl (5R)-5-C-cyano-2,3-O-isopropylidene-alpha-D-lyxofuranoside] (2), methyl 2,3-O-isopropylidene-alpha-D-mannofuranosiduronamide [methyl (5S)-5-C-carbamoyl-2,3-O-isopropylidene-alpha-D-lyxofuranoside; methyl (5S)-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosiduronamide] (3), methyl 2,3-O-isopropylidene-alpha-D-mannofuranosiduronic acid [methyl (5S)-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosiduronic acid] (4), methyl 5-deoxy-2,3-O-isopropylidene-5-ureido-beta-L-gulofuranosiduronamide [methyl (5R)-5-deoxy-2,3-O-isopropylidene-5-ureido-alpha-D-lyxo-hexofuranosiduronamide (5), and (4S,5S,6R)-5,6-dihydro-6-hydroxy-4,5-isopropylidenedioxy-4H-pyrido[2,1-e]imidazolidine-2',4'-dione [IUPAC name: (3aS,4R,8aS)-4-hydroxy-2,2-dimethyl-3a,8a-dihydro-4H-1,3-dioxa-4a,6-diaza-s-indacene-5,7-dione] (6), instead of the expected hydantoin derivative, were obtained from the Bucherer-Bergs reaction of methyl 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside (1). The structure of 6 was deduced from NMR and mass spectral data and confirmed by X-ray crystallography. The configuration at C-5 in 2-5 was confirmed by establishing the 5S configuration of 3 by X-ray crystallography. Conformations of the six- and five-membered rings in 3 and 6 are also discussed.     

Synthesis of O-alpha-D-glucopyranosyl-(1----4)-O-alpha -D-xylopyranosyl-(1----4)-O-alpha -D-xylopyranosyl-(1----4)-D-glucopyranose as a substrate analogue of alpha amylase

The tetrasaccharide a-D-Glcp-(1----4)-a-D-Xylp-(1----4)-a-D-Xylp-(1----4)-D- Glcp (1) has been synthesized, as a substrate analogue of alpha amylase, by silver perchlorate-catalyzed glycosylation of benzyl 2,3,6-tri-O-benzyl-4-O-(2,3-di-O-benzyl-a-D-xylopyranosyl)-beta-D- glucopyranoside (30) with 2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-a-D- glucopyranosyl)-a-D-xylopyranosyl chloride or by methyl triflate-promoted condensation of 30 with methyl 2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-a-D-glucopyranosyl)-1-thio- beta-D-xylopyranoside, followed by removal of protecting groups of the resulting tetrasaccharide derivative 40.     

The chemical structure of the polysaccharide from Dasyclonium incisum

The polysaccharide from Dasyclonium incisum was found to be an agar-type polymer, in which the 2-hydroxyl group on the 3,6-anhydrogalactosyl unit is partially substituted by a methyl ether, and the 4-hydroxyl group on the galactosyl unit is almost completely replaced by a sulphate ester group. Minor levels of other substitution patterns were also detected, including single branching xylose residues. Techniques used in determining the structure include selective hydrolysis, reductive hydrolysis followed by saccharide composition and methylation analysis, infrared and ¹³C-NMR spectroscopy.     

Regioselectivity in the sulfation of dermatan sulfate and methyl 4,6-O-benzylidene-alpha-D-idopyranoside.

The sulfation of dermatan sulfate by SO3-trimethylamine in N,N-dimethylformamide led to substitution initially at HO-6 of residues of 2-acetamido-2-deoxy-beta-D-galactopyranosyl 4-sulfate (1), to produce the 4,6-disulfate (6). When this step reached a level of greater than 50%, sulfation occurred with equal facility at HO-2 and HO-3 of residues of alpha-L-idopyranosyluronic acid (2), giving rise to a mixture of 2-,3-, and 2,3-disulfates. An analogous substitution pattern was observed for HO-2 and -3 of a simpler idopyranose unit, in the sulfation of methyl 4,6-O-benzylidene-alpha-D-idopyranoside (12). This lack of regioselectivity in the reaction of 2 (and 12) contrasts markedly with the high affinity of the reagent for HO-3 of residues of alpha-L-idopyranosyluronic acid present in a modified form of heparin. It is attributed to a difference between the two polymers in the relative orientation of their neighboring amino sugar residues, whereby there is an unobstructed access of the reagent in one instance, and hindrance of HO-2 selectively in the other. Enzymolysis by chondroitinase ABC was found to yield unsaturated disaccharide containing residues of 4,6-disulfate, as well as larger fragments containing unsaturated glycosyl groups derived from L-idopyranosyluronic acid 2-sulfate, evidence of a relatively broad enzyme specificity. The presence of extra sulfate groups in dermatan sulfate did not enhance its weak antithrombotic activity, as measured by anti Xa assay, in disagreement with earlier reports.     

Enhanced 3-O-sulfation of galactose in Asn-linked glycans and Maackia amurensis lectin binding in a new Chinese hamster ovary cell line

We report the characterization of two Chinese hamster ovary cell lines that produce large amounts of sulfated N-linked oligosaccharides. Clones 26 and 489 were derived by stable transfection of the glycosaminoglycan-deficient cell mutant pgsA-745 with a cDNA library prepared from wild-type cells. Peptide:N-glycanase F released nearly all of the sulfate label, indicating that sulfation had occurred selectively on the Asn-linked glycans. Hydrazinolysis followed by nitrous acid treatment at pH 4 and borohydride reduction yielded reduced sulfated disaccharides that comigrated with standard Gal3SO4beta1-4anhydromannitol. The disaccharides were resistant to periodate oxidation but became sensitive after the sulfate group was removed by methanolysis, indicating that the sulfate was located at C3 of the galactose residues. Maackia amurensis lectin bound to the sulfated glycopeptides on the cell surface and in free form, even after sialidase treatment. This finding indicates that the lectin requires only a charged group at C3 of the galactose unit and not an intact sialic acid. Growth of cells with chlorate restored sialidase sensitivity to lectin binding, indicating that sulfation and sialylation occurred largely at the same sites. The enhanced sulfation was due to elevated sulfotransferase activity that catalyzed transfer of sulfate from phosphoadenosine-5'-phosphosulfate to Galbeta1-4(3)GlcNAcbeta-O-naphthalenemethanol.     

Mutagenic and inactivating effects of methyl alkylaminosulfonates on Escherichia coli.

Methyl alkylamino methanesulfonates are mutagenic agents as shown by treating several strains of E. coli at pH 7. Methyl methylaminosulfonate (CH3-NH-SO3-CH3) was more efficient than methyl ethylaminosulfonate (C2H5-NH-SO3-CH3) which itself was more efficient than methyl isopropylaminosulfonate (C3H7-NH-SO3-CH3). Methyl methylaminosulfonate seemed to be at least as effective as methyl methanesulfonate (CH3-SO3-CH3). Methyl methylaminosulfonate produced a yield of up to 1% of auxotrophic mutants. All three new mutagens appeared to react according to the same mechanism by ester fission and methylation of nucleophilic groups as is known for methyl methanesulfonate. The reaction mechanism seems to be of the SN2 type.     

Synthèse du méthyl-2-acétamido-2-désoxy-β-D-glucofuranoside et de dérivés

Methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-β-D-glucofuranoside was prepared in excellent yield from methyl 2-benzamido-2-deoxy-5,6-O-isopropylidene-β-D-glucofuranoside by alkaline hydrolysis, followed by selective N-acetylation. Treatment with 60% acetic acid at room temperature gave syrupy methyl 2-acetamido-2-deoxy-β-D-glucofuranoside, characterized by a crystalline tri-O-p-nitrobenzoyl derivative. The same treatment, at 100° gave methyl 2-acetamido-2-deoxy-β-D-glucopyranoside. In an alternative procedure, the selective N-acetylation was performed after acetic acid hydrolysis of methyl 2-amino-2-deoxy-5,6-O-isopropylidene-β-D-glucofuranoside. Several derivatives of methyl 2-acetamido-2-deoxy-β-D-glucofuranoside were prepared and compared with the corresponding pyranosides. The furanoside structure was clearly demonstrated by mass spectrometry and periodate oxidation.     

Synthesis of the methyl thioglycosides of deoxy-N-acetyl-neuraminic acids for use as glycosyl donors.

Methyl 2-thioglycoside derivatives of 4-, 7-, 8-, and 9-deoxy-N-acetylneuraminic acids have been prepared as glycosyl donors for the synthesis of sialoglycoconjates. Reduction of a (phenoxy)thiocarbonyl group, selectively introduced at the 4 position of methyl [2-(trimethylsilyl)ethyl 5-acetamido-3,5-dideoxy-8,9-O-isopropylidene-D- glycero-alpha-D-galacto-2-nonulopyranosid]onate (1), gave the 4-deoxy compound, which was transformed via O-deisopropylidenation, acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, subsequent acetylation, and displacement of the 2-acetoxy group by a methylthio group, into methyl (methyl 5-acetamido-7,8,9-tri-O-acetyl-3,4,5-trideoxy-2-thio-D-manno-2- nonulopyranosid)onate (17). Methyl [2-(trimethylsilyl)ethyl 5-acetamido-8,9-di-O-acetyl-4-O-benzoyl- 3,5,7-trideoxy-alpha-D-galacto-2-nonulopyranosid]onate, prepared from 1 in five steps, and methyl [2-(trimethylsilyl)ethyl 5-acetamido-4,7,9-tri-O-acetyl-3,5,8-trideoxy-alpha-D-galacto-2- nonulopyranosid]onate, prepared from 1 in six steps, were converted via selective removal of the 2-(trimethylsilyl)ethyl group, O-acetylation, and displacement of the 2-acetoxy group by a methylthio group as described for 17, into the corresponding methyl 7- and 8-deoxy-2-thioglycosides. Reductive dechlorination of methyl [2-(trimethylsilyl)ethyl 5-acetamido-4,7-di-O-benzoyl-9-chloro-3,5,9-trideoxy-D-glycero-alpha-D-g alacto- 2-nonulopyranosid]onate, prepared from methyl [2-(trimethylsilyl)ethyl 5-acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosid++ +]onate by selective 9-O-tert-butyldimethylsilylation, benzoylation, removal of the 9-silyl group, and selective chlorination, gave a 9-deoxy compound. This was transformed, via O-debenzoylation, O-acetylation, selective removal of the 2(trimethylsilyl)ethyl group, 2-O-acetylation, 2-chlorination, displacement with potassium thioacetate, selective S-deacetylation, and S-methylation, into the methyl 2-thio-alpha-glycoside of 9-deoxy-N-acetylneuraminic acid.     

Convenient preparation of 3,5-anhydro- and 2,5-anhydropentofuranosides, and 5,6-anhydro-D-glucofuranose by use of the Mitsunobu reaction

Methyl 3,5-anhydro-alpha-D-xylofuranosides are obtained by use of the Mitsunobu reaction from 2-O-protected methyl alpha-D-xylofuranosides, which are easily prepared from D-xylose. The Mitsunobu reaction of methyl 3-N-benzylamino-3-deoxy- and 3-azido-3-deoxyarabinofuranosides, which are prepared from the conveniently available methyl 2,3-anhydro-alpha-D- and 2,3-anhydro-alpha-l-lyxofuranosides by nucleophilic ring opening, yields the corresponding methyl 2,5-anhydro-alpha-D- and 2,5-anhydro-alpha-l-arabinofuranosides. Ring opening of 3,5-anhydro-1,2-O-isopropylidene-alpha-D-xylofuranose with azide yields the corresponding 5-azido derivative. The structure and configuration of the products is confirmed by NMR spectroscopy. 5,6-Anhydro-1,2-O-isopropylidene-alpha-D-glucofuranose is formed by the Mitsunobu reaction of 1,2-O-isopropylidene-alpha-D-glucofuranose. Its structure is verified by single-crystal X-ray diffraction analysis.     

Identification of aromatic dihydroxy acids in biological fluids

3,5-Dihydroxyphenylpropionic acid, 3,5-dihydroxycinnamic acid and 2,3-dihydroxycinnamic acid were detected for the first time to be components of human urine. In the course of this investigation all constitutional isomers of dihydroxy-benzoic, -phenylpropionic, -phenylacetic and -cinnamic acid were synthesized. Mass spectra and retention indices of methyl and trimethylsilyl (TMS) derivatives were determined. In contrast to many other substituted aromatic compounds the mass spectra of methyl and TMS derivatives of dihydroxy aromatic acids often allow a firm distinction to be made between constitutional isomers: TMS derivatives of aromatic acids containing two hydroxy groups located in the ortho position to each other can be recognized by ions resulting from a primary cleavage reaction mainly in the side chain or ester group, followed by loss of tetramethylsilane. In methyl derivatives of 1,2,3-trisubstituted isomers, methoxy groups are lost much more easily from the ions corresponding to the benzylic cleavage than in other isomers. Methyl derivatives of dihydroxycinnamic acids containing at least one methoxy group in the ortho position to the side chain are characterized by a fragmentation reaction, corresponding to the loss of dimethyl ether. TMS and methyl derivatives of 3,5-dihydroxy aromatic acids show unique structure-specific fragmentation reactions.     

Identification and culturing of cyanobacteria isolated from freshwater bodies of Sri Lanka for biodiesel production

The present study was carried out to investigate cyanobacteria as a potential source for biodiesel production isolated from fresh water bodies of Sri Lanka. Semi mass culturing and mass culturing were carried out to obtain biomass for extracting total lipids. Fatty acid methyl ester (FAME) or biodiesel was produced from extracted lipid by trans-esterification reaction. FAME component was identified using gas chromatography (GC). Atotal of 74 uni-algal cultures were obtained from Biofuel and Bioenergy laboratory of the National Institute of Fundamental Studies (NIFS), Kandy, Sri Lanka. The total lipid content was recorded highest in Oscillatoria sp. (31.9 ± 2.01% of dry biomass) followed by Synechococcus sp. (30.6 ± 2.87%), Croococcidiopsis sp. (22.7 ± 1.36%), Leptolyngbya sp. (21.15 ± 1.99%), Limnothrixsp. (20.73 ± 3.26%), Calothrix sp. (18.15 ± 4.11%) and Nostoc sp. (15.43 ± 3.89%), Cephalothrixsp. (13.95 ± 4.27%), Cephalothrix Komarekiana (13.8 ± 3.56%) and Westiellopsisprolifica (12.80 ± 1.97%). FAME analysis showed cyanobacteria contain Methyl palmitoleate, Linolelaidic acid methyl ester, Cis-8,11,14-eicosatrienoic acid methyl ester, Cis-10-heptadecanoic acid methyl ester, Methyl myristate, Methyl pentadecanoate, Methyl octanoate, Methyl decanoate, Methyl laurate, Methyl tridecanoate, Methyl palmitoleate, Methyl pentadeconoate, Methyl heptadeconoate, Linolaidic acid methyl ester, Methyl erucate, Methyl myristate, Myristoloeic acid, Methyl palmitate, Cis-9-oleic acid methyl ester, Methyl arachidate and Cis-8,11,14-ecosatrieconoic acid methyl ester. The present study revealed that cyanobacteria isolated from Sri Lanka are potential source for biodiesel industry because of their high fatty acid content. Further studies are required to optimize the mass culture conditions to increase thelipid content from cyanobacterial biomass along with the research in the value addition to the remaining biomass.     

Lipase-catalysed preparation of acetates of 4-nitrophenyl beta-D-xylopyranoside and their use in kinetic studies of acetyl migration

Di-O-acetates and mono-O-acetates of 4-nitrophenyl beta-D-xylopyranoside were prepared by use of lipase PS-30. Polarity of organic solvents and reaction time affected the regioselectivity of the di-O-acetylation as well as the yields of monoacetates. The kinetics of acetyl groups migration in these derivatives was studied in aqueous media using HPLC. Migration of the acetyl group strongly depended on pH. The highest rate of acetyl migration was observed from O-2 to O-3 in both 2,4-di-O-acetate and 2-O-acetate. On the contrary, acetyl exchange between O-3 and O-4 in both directions was slower than between O-2 and O-3. The 2,3-di-O-acetate and 4-O-acetate showed to be the most stable towards acetyl migration. The 3,4-di-O-acetate and 4-O-acetate were dominant in the corresponding equilibration mixtures.