Improved preparations of some per-O-acetylated aldohexopyranosyl cyanides

3,4,6-Tri-O-acetyl-1,2-O-[1-(exo-, endo-cyano)ethylidene]-α-d-galacto- (1a/b), -α-d-gluco- (2a/b), and -β-d-manno-pyranose (3a/b) were stereoselectively isomerized to the corresponding per-O-acetylated 1,2-trans-aldohexopyranosyl cyanides in 75, 16, and 62% yield, respectively, by treatment with boron trifluoride etherate in dry nitromethane. The corresponding per-O-acetylated 1,2-cis-aldohexopyranosyl cyanides were obtained concurrently in respective yields of 1.9, 0.9, and 4.8%. The per-O-acetylaldohexopyranosyl cyanide products were found stable to the reaction conditions and were readily isolated following completion of the rearrangement. It had previously been proved that reaction of 2,3,4,6-tetra-O-acetyl-α-d-manno- and -gluco-pyranosyl bromide with mercuric cyanide in nitromethane generates, in the ratio of ∼1:1, the desired 1,2-trans-glycosyl cyanides and the corresponding 1,2-O-(1-cyanoethylidene) isomers (3a/b and 2a/b, respectively). Treatment of these reaction-mixtures with boron trifluoride etherate in nitromethane effected the rearrangement of 3a/b and 2a/b, thereby facilitating the isolation, and increasing the overall yields, of the per-O-acetylated 1,2-trans-d-manno and -gluco-pyranosyl cyanides (58 and 30% total yield, respectively) relative to the earlier procedures. The boron trifluoride etherate-mediated reaction of per-O-acetyl-α- and -β-d-galacto, -α- and -β-d-gluco-, -α-d-manno-, and -2-deoxy-2-phthalimido-β-d-gluco-pyranoses with trimethylsilyl cyanide in nitromethane was also investigated. This reaction provides a “one-flask” synthesis of the corresponding per-O-acetylated 1,2-trans-aldohexopyranosyl cyanides in which 1,2-O-(1-cyanoethylidene) derivatives are isomerized in situ. Finally, improved preparations of the (not readily accessible) per-O-acetylated 1,2-cis-d-manno- and -gluco-pyranosyl cyanides are described. Thus, 2,3,4,6-tetra-O-acetyl-α- and -β-d-mannopyranosyl cyanide (48 and 16% total yield, respectively) and -α- and -β-d-glucopyranosyl cyanide (12 and 39% total yield, respectively) were synthesized by fusion of the corresponding -α-d-glycosyl bromides with mercuric cyanide.     

Studies on the origin of stereoselectivity in the synthesis of 1,2-trans glycofuranosyl azides

The stereoselectivity of the 1,2-trans directed, Lewis acid-catalysed azidation of peracylated furanoses was found to depend on the reactivity of the azide donor (azide nucleophilicity) and the configuration at the anomeric centre relative to the neighbouring 2-O-acyl group. Reactions of 1,2-trans glycosyl esters with highly nucleophilic azide donors, generated from SnCl4 and Me3SiN3, were stereospecific. The results are interpreted in terms of the rapid reaction of the azide species with bicyclic 1,2-acyloxonium (1,2-O-alkyliumdiyl-D-glycofuranose) ions, which were the primarily formed reactive intermediates. When using 1,2-cis glycosyl esters as starting materials the selectivity was reduced (90-94% de); the same is true with 1,2-trans counterparts if less nucleophilic Me3SiN3 in combination with Me3SiOTf catalyst was used. This occurred due to the appearance of the more reactive but less selective oxocarbenium (glycofuranoxonium) ions either as primarily formed reactive intermediates in the former case or after equilibration with acyloxonium ions in the latter case. Protected 1,2-trans beta-D-glycofuranosyl azides with ribo, xylo and 3-deoxy-erythro-pento configurations were best prepared from the corresponding glycosyl esters using 0.05 equivalents of SnCl4, i.e., under anomerization-free conditions. Azidation of methyl glycofuranosides proceeds with inferior (80-90% de) and less predictable selectivity irrespective of the starting anomeric configuration.     

Effects of dichloroethene isomers on the induction and activity of butane monooxygenase in the alkane-oxidizing bacterium "Pseudomonas butanovora"

We examined cooxidation of three different dichloroethenes (1,1-DCE, 1,2-trans DCE, and 1,2-cis DCE) by butane monooxygenase (BMO) in the butane-utilizing bacterium "Pseudomonas butanovora." Different organic acids were tested as exogenous reductant sources for this process. In addition, we determined if DCEs could serve as surrogate inducers of BMO gene expression. Lactic acid supported greater rates of oxidation of the three DCEs than the other organic acids tested. The impacts of lactic acid-supported DCE oxidation on BMO activity differed among the isomers. In intact cells, 50% of BMO activity was irreversibly lost after consumption of approximately 20 nmol mg protein(-1) of 1,1-DCE and 1,2-trans DCE in 0.5 and 5 min, respectively. In contrast, a comparable loss of activity required the oxidation of 120 nmol 1,2-cis DCE mg protein(-1). Oxidation of similar amounts of each DCE isomer ( approximately 20 nmol mg protein(-1)) produced different negative effects on lactic acid-dependent respiration. Despite 1,1-DCE being consumed 10 times faster than 1,2,-trans DCE, respiration declined at similar rates, suggesting that the product(s) of oxidation of 1,2-trans DCE was more toxic to respiration than 1,1-DCE. Lactate-grown "P. butanovora" did not express BMO activity but gained activity after exposure to butane, ethene, 1,2-cis DCE, or 1,2-trans DCE. The products of BMO activity, ethene oxide and 1-butanol, induced lacZ in a reporter strain containing lacZ fused to the BMO promoter, whereas butane, ethene, and 1,2-cis DCE did not. 1,2-trans DCE was unique among the BMO substrates tested in its ability to induce lacZ expression.     

The synthesis of cyclic imidates from amides of glucuronic acid and investigation of glycosidation reactions

The synthesis of novel cyclic glycosyl imidates and an investigation of their potential as donors in glycosidation reactions is described. The results show that 1,2-cis glycosides obtained from the reactions of glycosyl acetates or cyclic imidates, each derived from amides of glucuronic acid, result from the anomerisation of initially formed 1,2-trans glycosides.     

N-Glycosidation of D-arabino-hex-2-ulosonic acid

Two approaches to N-functionalized D-arabino-hex-2-ulosonic acid derivatives were established by nucleophilic substitution of methyl (3,4,5-tri-O-acetyl-beta-D-arabino-hex-2-ulopyranosyl)onate bromide (1). Reaction of 1 with amino compounds in the presence of mercury(II) cyanide led to the 2,3-cis configured beta-D-arabino N-glycosides. On the other hand, the reaction of bromide 1 with azide, followed by catalytic hydrogenation led to 2,3-trans alpha-D-arabino glycosyl amine methyl 3,4,5-tri-O-acetyl-2-amino-alpha-D-arabino-hex-2-ulopyranosonate, which was easily rearranged to the thermodynamically more stable beta-D-arabino N-acetyl derivative methyl 4,5-di-O-acetyl-2-acetylamino-3-hydroxy-beta-D-arabino-hex-2-ulopyranosonate. The assignment of configuration of the tertiary anomeric centre and conformation of all products was based on 1H NMR H,H coupling constants and NOE difference experiments.     

13C solid-state NMR chemical shift anisotropy analysis of the anomeric carbon in carbohydrates

(13)C NMR solid-state structural analysis of the anomeric center in carbohydrates was performed on six monosaccharides: glucose (Glc), mannose (Man), galactose (Gal), galactosamine hydrochloride (GalN), glucosamine hydrochloride (GlcN), and N-acetyl-glucosamine (GlcNAc). In the 1D (13)C cross-polarization/magic-angle spinning (CP/MAS) spectrum, the anomeric center C-1 of these carbohydrates revealed two well resolved resonances shifted by 3-5ppm, which were readily assigned to the anomeric alpha and beta forms. From this experiment, we also extracted the (13)C chemical shift anisotropy (CSA) tensor elements of the two forms from their spinning sideband intensities, respectively. It was found out that the chemical shift tensor for the alpha anomer was more axially symmetrical than that of the beta form. A strong linear correlation was obtained when the ratio of the axial asymmetry of the (13)C chemical shift tensors of the two anomeric forms was plotted in a semilogarithmic plot against the relative population of the two anomers. Finally, we applied REDOR spectroscopy to discern whether or not there were any differences in the sugar ring conformation between the anomers. Identical two-bond distances of 2.57A (2.48A) were deduced for both the alpha and beta forms in GlcNAc (GlcN), suggesting that the two anomers have essentially identical sugar ring scaffolds in these sugars. In light of these REDOR distance measurements and the strong correlation observed between the ratio of the axial asymmetry parameters of the (13)C chemical shift tensors and the relative population between the two anomeric forms, we concluded that the anomeric effect arises principally from interaction of the electron charge clouds between the C-1-O-5 and the C-1-O-1 bonds in these monosaccharides.     

Stereoselective synthesis of 1,2-cis- and 2-deoxyglycofuranosyl azides from glycosyl halides

Protected 1,2-cis glycofuranosyl azides with alpha-D-ribo, beta-D-arabino and 2-deoxy-2-fluoro-beta-D-arabino configurations were efficiently prepared from the appropriate 1,2-trans glycosyl halides bearing non-participating 0-2 substituent by inversion with sodium azide under phase transfer catalytic conditions (80-85% yields, 90-96% de). The same method failed to result in sufficiently good beta-selectivity starting from 2-deoxy-3,5-di-O-(p-toluoyl)-alpha-D-ery-thro-pentofuranosyl chloride (5alpha) (40% de). The selectivity in favour of the protected 2-deoxy-beta-D-erythro-pentofura-nosyl azides was greatly improved (74-80% de) by treating 5alpha and its p-chlorobenzoyl analog 6alpha with cesium or potassium azide in dimethylsulfoxide at room temperature (83-85% yields).     

Synthesis of 4-cyano and 4-nitrophenyl 1,6-dithio-D-manno-, L-ido- and D-glucoseptanosides possessing antithrombotic activity

1,6-Anhydro-3,4-O-isopropylidene-1-thio-D-mannitol was converted into its sulfoxide which after hydrolysis, acetylation and subsequent Pummerer rearrangement gave the penta-O-acetyl-1-thio-D-mannoseptanose anomers in excellent yield. This anomeric mixture was used as donor for the glycosylation of 4-nitro- and 4-cyanobenzenethiol in the presence of boron trifluoride etherate and trimethylsilyl triflate, respectively, to yield the corresponding thioseptanosides in high yield. The same strategy was applied for the synthesis of the corresponding L-idothioseptanosides using 1,6-anhydro-3,4-O-isopropylidene-1-thio-L-iditol as starting material. The penta-O-acetyl-D-glucothioseptanose donors could not be synthesised the same way, as the Pummerer reaction of the corresponding tetra-O-acetyl-1,6-thioanhydro-1-thio-D-glucitol sulfoxides led to an inseparable mixture of the corresponding L-gulo- and D-glucothioseptanose anomers. Therefore, D-glucose diethyl dithioacetal was converted via its 2,3,4,5-tetra-O-acetyl-6-S-acetyl derivative into an anomeric mixture of its 6-thio-septanose and -furanose peracetates which could be separated by column chromatography. Condensation of the 6-thio-glucoseptanose peracetates with 4-cyano- and 4-nitrobenezenethiol in the presence of boron trifluoride etherate afforded anomeric mixtures of the corresponding thioseptanosides. The D-manno-, L-ido- and D-glucothioseptanosides obtained after Zemplén deacetylation of these mixtures were tested for their oral antithrombotic activity.     

Syntheses of amphiphilic glycosylamides from glycosyl azides without transient reduction to glycosylamines

Protected glycosyl azides react with acyl chlorides in the presence of triphenylphosphine to afford glycosylamides in high yields, at room temperature. Starting from the beta-glycosyl azides, the reaction is highly stereoselective and occurs with retention of configuration, whereas the alpha-azido anomers display a lower stereoselectivity giving rise to alpha/beta mixtures of glycosylamides. The reaction was applied to several monosaccharidic azides and to lactosyl azide with various acyl chlorides; it was shown to be of general use for preparing 1,2-trans beta-glycosylamides.     

Regiospecific effect of 1-octanol on cis-trans isomerization of unsaturated fatty acids in the solvent-tolerant strain Pseudomonas putida S12

The solvent-tolerant bacterium Pseudomonas putida S12, which adapts its membrane lipids to the presence of toxic solvents by a cis to trans isomerization of unsaturated fatty acids, was used to study possible in vivo regiospecificity of the isomerase. Cells were supplemented with linoleic acid (C18:2delta9-cis,delta12-cis), a fatty acid that cannot be synthesized by this bacterium, but which was incorporated into membrane lipids up to an amount of 15% of total fatty acids. After addition of 1-octanol, which was used as an activator of the cis-trans isomerase, the linoleic acid was converted into the delta9-trans,delta12-cis isomer, while the delta9-cis,delta12-trans and delta9-trans,epsilon12-trans isomers were not synthesized. Thus, for the first time, regiospecific in vivo formation of novel, mixed cis/trans isomers of dienoic fatty acid chains was observed. The maximal conversion (27-36% of the chains) was obtained at 0.03-0.04% (v/v) octanol, after 2 h. The observed regiospecificity of the enzyme, which is located in the periplasmic space, could be due to penetration of the enzyme to a specific depth in the membrane as well as to specific molecular recognition of the substrate molecules.     

Functional characterization of Delta3,Delta2-enoyl-CoA isomerases from rat liver.

The degradation of unsaturated fatty acids by beta-oxidation involves Delta(3),Delta(2)-enoyl-CoA isomerases (enoyl-CoA isomerases) that catalyze 3-cis --> 2-trans and 3-trans --> 2-trans isomerizations of enoyl-CoAs and the 2,5 --> 3,5 isomerization of dienoyl-CoAs. An analysis of rat liver enoyl-CoA isomerases revealed the presence of a monofunctional enoyl-CoA isomerase (ECI) in addition to mitochondrial enoyl-CoA isomerase (MECI) in mitochondria, whereas peroxisomes contain ECI and multifunctional enzyme 1 (MFE1). Thus ECI, which previously had been described as peroxisomal enoyl-CoA isomerase, was found to be present in both peroxisomes and mitochondria. This enzyme seems to be identical with mitochondrial long-chain enoyl-CoA isomerase (Kilponen, J.M., Palosaari, P.M., and Hiltunen, J.K. 1990. Biochem. J. 269, 223-226). All three hepatic enoyl-CoA isomerases have broad chain length specificities but are distinguishable by their preferences for one of the three isomerization reactions. MECI is most active in catalyzing the 3-cis --> 2-trans isomerization; ECI has a preference for the 3-trans --> 2-trans isomerization, and MFE1 is the optimal isomerase for the 2,5 --> 3,5 isomerization. A functional characterization based on substrate specificities and total enoyl-CoA isomerase activities in rat liver leads to the conclusion that the 3-cis --> 2-trans and 2,5 --> 3,5 isomerizations in mitochondria are catalyzed overwhelmingly by MECI, whereas ECI contributes significantly to the 3-trans --> 2-trans isomerization. In peroxisomes, ECI is predicted to be the dominant enzyme for the 3-cis --> 2-trans and 3-trans --> 2-trans isomerizations of long-chain intermediates, whereas MFE1 is the key enzyme in the 2,5 --> 3,5 isomerization.     

]A potentially versatile synthesis of glycosides

Phenyl 1-thio-D-glucopyranosides in the presence of mercury(II) salts are readily solvolysed to give alkyl D-glucopyranosides with inverted anomeric configuration. Methanolyses of the β and α anomers afford the methyl α and β-glycosides which were isolated in yields of 74 and 87%, respectively; n.m.r. examinations indicated that, whereas the β-glycoside was produced stereospecifically, the α-glycoside was formed together with ≈6% of its β isomer. The approach can be extended to the synthesis of complex glycosides (the α anomers of which are of special interest) as was illustrated by the preparation of cholestanyl and 1-naphthyl α-D-glucopyranoside and a disaccharide derivative.     

Biosynthesis of trans,trans- and cis,trans-farnesols by soluble enzymes from tissue cultures of Andrographis paniculata

A cell-free system obtained from tissue cultures of Andrographis paniculata produces 2-trans,6-trans-farnesol (trans,trans-farnesol) and 2-cis,6-trans-farnesol (cis,trans-farnesol) (5:1), incorporating 10% of the radioactivity from 3R-[2-(14)C]mevalonate. There is total loss of (3)H from 3RS-[2-(14)C,(4S)-4-(3)H(1)]mevalonate and total retention from the (4R) isomer in both the trans,trans-farnesol and cis,trans-farnesol formed. When 3RS-[2-(14)C,5-(3)H(2)]mevalonate is used as substrate, there is total retention of (3)H in the trans,trans-farnesol, but loss of one-sixth of the (3)H in the cis,trans-farnesol. With (1R)- and (1S)-[4,8,12-(14)C(3),1-(3)H(1)]-trans,trans -farnesol and (1R)- and (1S)-[4,8,12-(14)C(3),1-(3)H(1)]-cis, trans-farnesol as substrates, the label is lost from the (1R)-cis,trans and (1S)-trans,trans isomers but retained in the (1R)-trans,trans and (1S)-cis,trans isomers; this shows that the pro-1S hydrogen is exchanged in the conversion of trans,trans-farnesol into cis,trans-farnesol and the pro-1R hydrogen in the conversion of cis,trans-farnesol into trans,trans-farnesol. (1R)-[1-(3)H(1)]-trans,trans-Farnesol and (1R)-[1-(3)H(1)]-cis,trans-farnesol have been synthesized by asymmetric chemical synthesis and exchanged with liver alcohol dehydrogenase. Both the trans- and the cis-alcohol exchange the pro-1R hydrogen atom.     

Investigations of different carbohydrate anomers in copper(II) complexes with D-glucose, D-fructose, and D-galactose by Raman and EPR spectroscopy

With the aim of verifying different carbohydrate anomers coordinated to copper(II) ions, some copper(II) complexes with D-glucose (Glc), D-fructose (Fru), and D-galactose (Gal) were prepared and investigated by spectroscopic techniques. Their compositions were verified by elemental, ICP-AES and thermal analyses, in addition to conductivity measurements. The compounds isolated were consistent with the formula Na2[Cu2(carbohydrate)3].8H2O and Na[Cu2(carbohydrate)3].6H2O for the aldoses Glc and Gal, respectively, and Na2[Cu3(carbohydrate)4].8H2O in the case of the ketose, Fru. EPR spectra of these solids showed a rhombic environment around the metal center and suggested the presence of different anomers of the carbohydrates in each case. By Raman spectroscopy, it was possible to verify the predominance of the beta anomer of d-glucose in the corresponding copper complex, while in the free ligand the alpha anomer is predominant. In the case of the analogous complex with d-galactose, the spectrum of the complex shows bands of both anomers (alpha and beta) in approximately the same relative intensities as those observed in the isolated free ligand spectrum. On the other hand, for the complex with d-fructose a mixture of both furanose (five-membered ring) and pyranose (six-membered ring) structures was detected with prevalence of the furanose structure. Based on variations in the relative intensities of characteristic Raman bands, the binding site for copper in the fructose ligand was identified as most likely the 1-CH2OH and the anomeric 1-OH, while in beta-D-glucose it is presumably the anomeric 1-OH and the O-5 atom. These results indicated that EPR and Raman spectroscopy are suitable supporting techniques for the characterization of carbohydrate anomers coordinated to paramagnetic ions.     

Reductive and oxidative synthesis of saturated and unsaturated fatty aldehydes

Saturated and unsaturated fatty aldehydes were synthesized 99+% pure with yields of up to 80% by the reduction of 1-acylaziridines with lithium aluminium hydride, and in yields of up to 87% by oxidation of the corresponding alcohol with 1-chlorobenzotriazole. It was found for the reduction that optimum aldehyde yield was obtained with a mole ratio of reactants, consisting of acid chloride-ethylenimine-triethylamine-LiAlH(4), equal to 1:2:2:2. Optimum conditions for alcohol oxidation were found to be a mole ratio of oxidant to alcohol of 1:1.3 with refluxing for 45 min in methylene chloride containing 25% pyridine. Methods for the purification of the final product are also described. Purity criteria were thin-layer and gas-liquid chromatography and infrared and nuclear magnetic resonance spectroscopy.     

Some properties of synthetic fucopyranosylserines and -threonines

alpha Fuc-Ser, alpha Fuc-Thr, beta Fuc-Ser, and beta Fuc-Thr were synthesized stereoselectively in good yields, and their properties were investigated. beta-Fucosylserine (and -threonine) was synthesized by Koenigs-Knorr reaction of per-O-acetylfucopyranosyl bromide with N-carbobenzoxy-L-serine (and -threonine) benzyl ester using mercuric cyanide, followed by hydrogenolysis and deacetylation. alpha-Fucosylserine (and -threonine) was synthesized by the halide-ion catalyzed reaction of per-O-benzylfucopyranosyl bromide with the serine (and threonine) derivative described above, followed by hydrogenolysis. These substances each gave a single peak on an amino acid analyzer. The anomeric configurations of these compounds were determined by 1H-NMR spectroscopy, optical rotation measurement and enzymatic degradations of these compounds. On acid hydrolysis, alpha Fuc-Ser and alpha Fuc-Thr were more rapidly hydrolyzed than the corresponding beta-series compounds. Under mild alkaline conditions in the presence of sodium borohydride, per-protected beta Fuc-Thr released about 50% of fucose but free beta Fuc-Thr did not However, free alpha Fuc-Thr and beta Fuc-Thr were cleaved to give acetylated fucose during acetylation with acetic anhydride-pyridine. alpha-L-Fucosidases, which were purified from abalone and rabbit livers by affinity chromatography, acted very well on alpha Fuc-Ser and alpha Fuc-Thr, but not on the beta-series compounds.     

Synthesis and characterisation of N-glycosyl amines from the reaction between 4,6-O-benzylidene-D-glucopyranose and substituted aromatic amines and also between 2-(o-aminophenyl)benzimidazole and pentoses or hexoses

Twelve N-glycosyl amines were synthesised using 4,6-O-benzylidene-D-glucopyranose and different substituted aromatic amines, including some diamines that resulted in bis-glycosyl amines. Another set of six N-glycosyl amines was synthesised using different hexoses and pentoses and 2-(o-aminophenyl)benzimidazole. All compounds were isolated as solid products and purified, their elemental compositions were established, and these were characterised by NMR (1H and 13C), UV-Vis, and FTIR spectroscopy, by FAB mass spectrometry (molecular-ion peaks gave molecular weights), and by their optical rotations. While the protected saccharide, 4,6-O-benzylidene-D-glucopyranose, exists as a mixture of beta and alpha anomers in solution, the corresponding N-glycosyl amines were of only the beta anomeric form as determined by NMR and FTIR spectroscopy. On the other hand, N-glycosyl amines synthesised from 2-(o-aminophenyl)benzimidazole prefer the alpha anomeric form, and in two cases a mixture of both the beta and the alpha anomers were observed. The trends observed in the chemical shifts were compared among different products.     

Recent knowledge and innovations related to hexofuranosides: structure, synthesis and applications

Hexofuranosides are widely spread in nature, and notably in numerous pathogenic microorganisms. This particular five-membered ring for hexosides leads to novel biological properties and, as usual in glycochemistry, to completely different reactivity and selectivity. Far from being exhaustive, this review will first focus on the structure of the oligosaccharidic part of hexofuranosyl conjugates found in natural sources. Original syntheses will then be presented, stressing more particularly on the development of chemical and chemo-enzymatic tools for the access to 1,2-trans or 1,2-cis linkages. Finally, innovative applications related to biological, chemical and physicochemical fields for both natural and synthetic hexofuranosyl compounds will be described.     

D-Galactose 6-phosphate: anomeric distribution and analysis of its synthesis from D-galactose and polyphosphoric acid

D-Galactose 6-phosphate as synthesized by direct phosphorylation of D-galactose with polyphosphoric acid is contaminated with two of its positional isomers. These were separated from D-galactose 6-phosphate and from each other, and identified as D-galactose 3- and 5-phosphate by enzymic, chromatographic, and mass-spectral analysis. The previous misidentification of these isomers as furanose forms of D-galactose 6-phosphate has led to erroneous reports concerning the anomeric distribution of D-galactose 6-phosphate. The anomeric distribution of D-galactose 6-phosphate in a purified preparation was determined by gas-liquid chromatography and ¹³C-n.m.r. spectroscopy to be 32% α-pyranose, 64% β-pyranose, and no more than 4% furanose anomers.     

Preparation of anomeric pairs of 1-thioglycosides: use of anomerization catalyzed by boron trifluoride

Anomeric pairs of some alkyl 1-thioaldopyranosides of d-galactose, d-glucose, d-mannose, 2-acetamido-2-deoxy-d-glucose, 2-acetamido-2-deoxy-d-galactose, and l-fucose were prepared. The per-O-acetylated, 1,2-trans anomers of 6-(trifluoroacetamido)hexyl 1-thioaldopyranosides and 5-(methoxycarbonyl)pentyl 1-thioaldopyranosides were anomerized with boron trifluoride in dichloromethane. The anomeric mixtures were then separated by chromatography, using columns of either silica gel or an ion-exchange resin. De-blocking of the separated compounds provided pure anomers of 6-aminobexyl 1-thioaldopyranosides or 5-carboxypentyl 1-thioaldopyranosides. The aglycons of the latter glycosides were further extended by reaction with aminoacetaldehyde diethyl acetal, which, after deacetalization of the products, provided an ω-aldehydo group. These series of glycosides could be readily coupled to proteins or solid matrices.