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The article traces the history of the journal Carbohydrate Research from its debut in 1964 and its subsequent evolution to the present day, viewed from the perspective of one of the founding editors who served as a receiving editor until 2005. The concept of an international journal focused on the broad aspects of carbohydrate science found ready acceptance in the research community, and its volumes now serve as a unified archive of a significant proportion of published research data on all molecular aspects of carbohydrates. Changes in the editor line-up over the years are noted, along with the transition to electronic publishing, and the role of key people in the Elsevier Company toward the success of the journal.

Acetylated d -pentose diethyl dithioacetals were coupled by way of 1-bromo-1-ethylthio derivatives with 2,4-bis(trimethylsilyl)thymine to afford diastereomeric pairs of acyclic-sugar nucleoside analogues bearing a thymin-1-yl and an ethylthio group at C-1. Free-radical desulfurization by the action of tributylstannane removed the ethylthio group to afford the corresponding acetylated 1-(1-deoxy- d -pentitol-1-yl)thymines and subsequently the free title compounds in the arabino, lyxo, ribo, and xylo series. Conformations of the intermediates and products were studied in detail and the final products were evaluated for their potential as agents active against plant viruses and rice blast fungus.

1,6-Anhydro-4-deoxy-4-diazo-2,3-O-isopropylidene-β- d -lyxo-hexopyranose (4) is a stable crystalline compound readily accessible by an improved synthetic procedure. It has been used as a model for evaluating the reactivity of the diazo group, when not stabilized by an adjacent carbonyl function, in a rigid chiral matrix. A range of carbene-type, electrophile-promoted, and 1,3-dipolar reactions were evaluated, leading to 4,4′-alkene dimers, 4-deoxy-3-enose and related derivatives, 4,4-dihalo compounds, 4-spirocyclopropane derivatives, 4-spiropyrazole structures, and by skeletal rearrangement, branched-chain anhydropentose structures having a bicyclo[2.2.2] skeleton.

The methyl beta-glycoside of the title sugar, obtained from 2-deoxy-2-fluoro-beta-D-glucopyranose tetraacetate by a sequence with detailed characterization of all intermediates, was converted by acetolysis-bromination into 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl bromide, coupling of which with (7S,9S)-4-demethoxydaunomycinone afforded the 3,4-diacetate of 4-demethoxy-9-O-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl)daunomycinone (19). The antitumor-active 19 was converted by way of its 14-bromo derivative into the 14-hydroxy analogue, the antitumor-active 4-demethoxyadriamycinone glycoside 21.

Based on a literature precedent, preparation of methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-mannopyranoside (18) was attempted via fluorination of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-altropyranoside with diethylaminosulfur trifluoride (DAST). Contrary to expectations, the reaction took place with retention of configuration at the site of the fluorination yielding methyl 4-azido-2-O-benzyl-3,4,6-trideoxy-3-fluoro-alpha-D-altropyranoside. Treatment with DAST of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-allopyranoside (8), or its 2-(p-methoxybenzyl) analog 9 resulted in fluorination with inversion of configuration at position 3, to give the corresponding 3-deoxy-3-fluoro glucopyranosides 10 and 11, respectively. Accordingly, compound 18 was prepared from 11, by de-p-methoxybenzylation at O-2, followed by inversion of configuration at C-2 in the resulting methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-glucopyranoside. The 2-O-methyl analog of 18 (19) was prepared by methylation of 18. Compounds 18 and 19 were converted, conventionally, into the 3-fluoro analogs of the terminal determinants of the O-PS of Vibrio cholerae O:1, serotype Inaba and Ogawa, respectively.

3-Deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) (1) acts as a tetradentate ligand of the N2S2 type which forms stable coordination complexes with metal(II) cations. The Cu(II), Pt(II), and Pd(II) chelates (2, 4, and 6, respectively) of 1 were synthesized and characterized by elemental analysis and NMR spectroscopy. The NMR spectra of the Pt complex (4) showed the coupling of H-1 and C-1, C-2 of the bis(thiosemicarbazone) with 195Pt (33.7% naturally occurring), which supports the structure proposed for the chelate. The complexes 2, 4, and 6 were acetylated to give the corresponding tri-O-acetyl derivatives 3, 5, and 7. Elimination of Cu(II) from 3 with hydrogen sulfide afforded 8, the tri-O-acetyl derivative of 1. Preliminary studies have shown antiviral activity of chelates 2, 4, and 6 against poliovirus type 1.

This article reviews recent developments in the methodology for the measurement of anthocyanins that offer several advantages over classical methods of analysis. The use of UV-diode array and mass spectrometric (MS) detectors, with improved methods of liquid chromatography analysis has facilitated identification of these analytes. The use of capillary electrophoresis (CE) analysis of the anthocyanins under acid conditions has significantly increased peak resolution and improved the detection limits by several orders of magnitude. CE offers the advantage of economies of very small sample size, very small solvent consumption, and short analysis times along with the future possibility of being combined with MS detection.

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.

This study compares conventional solid–liquid extraction, supercritical fluid extraction (SFE), and pressurized fluid extraction (PFE) for their efficiency in extracting xanthones and flavanones from the root bark of the osage orange tree (Maclura pomifera). Seven compounds were extracted from the plant material by solvent extraction at room temperature for 48 h. The same compounds were removed from the root bark by 45- and 35-min extractions using SFE and PFE, respectively, and under optimized conditions, in same or higher yields than those obtained by the conventional 48-h solvent extraction. Although all seven compounds were present in the SFE extracts when only CO2 was used as the fluid, the addition of 20 vol.% methanol (MeOH) to the CO2 proved essential for achieving high yields. Use of SFE with CO2–MeOH also led to the recovery of an additional flavanone from a wet sample of root bark. This flavanone is absent from the conventional solvent extracts and appears in small amounts in the PFE extracts. An optimized LC separation for the analysis of the different extracts is presented, and it is demonstrated that the separation of xanthones and flavanones is considerably improved by the use of deactivated C18 columns in conjunction with a mobile phase containing acetonitrile and a weak organic acid.

The 4,6-benzylidene acetal of methyl 2-deoxy-2-fluoro-α,β- d -glucopyranoside underwent inversion at C-3 via an oxidation–reduction sequence, and treatment of the derived 3-acetate with N -bromosuccinimide in carbon tetrachloride gave methyl 3- O -acetyl-4- O -benzoyl-6-bromo-2,6-dideoxy-2-fluoro-α- d -allopyranoside ( 6 ). Dehydrobromination of 6 and reduction of the resultant 5,6-ene gave the 5-epimer of 6 , which after removal of the ester substituents, afforded the title compound in good overall yield.

The title dithioxyloside 1 , an orally active antithrombotic agent, as its 2,3-isopropylidene acetal, was converted into the corresponding glycos-4-ulose, which served as precursor via reduction to the 4-epimer of 1 and via oximation–reduction to the 4-acetamido-4-deoxy 4-epimer of 1 .

Preparative routes for anomerically specific 1- C -allylation of 2-amino-2-deoxy sugars have been evaluated in a comparative study of various N -substituents and aglycons as precursors for glycosyl radicals that effectively capture an allyl group from allyltributyltin. The crystalline triacetate 4 of 3-(2-acetamido-2-deoxy- α - d -glucopyranosyl)-1-propene ( 6 ) was obtained in 70% yield when 2-acetamido-3,4,6-tri- O -acetyl-2-deoxy- α - d -glucopyranosyl chloride ( 1 ) was treated with allyltributyltin under free-radical conditions, whereas the corresponding bromide 3 led only to an oxazolidine derivative; the β -1-ethylxanthate analogue of 1 gave 4 , but in only 25% yield. The 2-trifluoroacetamido 1-bromide analogue of 1 was also an effective radical source, giving the 2-trifluoroacetamido analogue 8 of 4 in 60% yield. The free amino analogue 7 of 4 was conveniently obtained via the 2- p -methoxybenzylideneamino 1-bromide analogue of 1 . Use of 3,4,6-tri- O -acetyl-2-deoxy-2-phthalimido- β - d -glucopyranosyl bromide as radical precursor allowed stereospecific access to β -1- C -allyl derivatives of the amino sugar. The crystalline galactosamine analogue 12 of 4 was obtained by using the galacto analogue of chloride 1 , but the corresponding manno chloride gave only an oxazoline product. The 1- C -allylated amino sugar derivatives are conformationally more mobile than derivatives not having a 1- C -linked substituent.

The four major anthocyanins present in juice of the blackcurrant (Ribes nigrum) may be completely separated by capillary zone electrophoresis under strongly acidic conditions. The separation, resolution and peak shapes of the anthocyanins are critically influenced by the pH of the running buffer and the presence of an organic solvent. Fused-silica and polyacrylamide-coated capillary columns were evaluated for their ability to resolve the closely migrating analytes. Optimum qualitative separation was achieved on a fused-silica capillary with a phosphate running buffer containing 30% (v/v) acetonitrile at an apparent pH of 1.5.

3,4,5,6-Tetra-O-benzoyl-D-glucose diethyl dithioacetal (2) reacts with ethanethiol under acidic conditions to afford 3,4,5,6-tetra-O-benzoyl-2-S-ethyl-2-thio-D-mannose (3), the stereochemistry at C-2 of which has been assigned by chemical conversions on its debenzoylated derivative, the crystalline 2-S-ethyl-2-thio-D-mannose diethyl dithioacetal (4). In the presence of mercuric chloride (1.1 molar equiv), 4 is converted into crystalline ethyl 2-S-ethyl-1,2-dithio-alpha-D-mannofuranoside (5). Complete demercaptalation of 4 affords syrup 2-S-ethyl-2-thio-D-mannopyranose (6), which was characterized as its phenylhydrazone 7 and the crystalline alpha-pyranose tetraacetate 9. Extended treatment of 4 with mercuric chloride and aqueous sodium hydrogencarbonate resulted in isolation of 6, along with its crystalline 2-epimer, 2-S-ethyl-2-thio-beta-D-glucopyranose (10). Remercaptalation of 6 affords the manno diethyl dithioacetal 4 as the major product, whereas similar treatment of 10 yields ethyl 2-S-ethyl-1,2-dithio-alpha-D-glucopyranoside (13). The mechanism of conversion of 2 into 3, as well as the unusually facile interconversion of 2-S-ethyl-2-thio-D-mannose (6) and its D-gluco epimer 10, has been investigated.

Acyclic trans -2,3-unsaturated aldoheptonate derivatives ( 1–9 ) obtained from d -aldopentoses by Witting chain-extension served as dienophiles for a detailed comparative study of their asymmetric Diels-Alder cycloaddition with cyclopentadiene. Cycloaddition under uncatalyzed thermal conditions gave mixtures of the four possible stereoisomeric norbornene adducts. The endo:exo ratios and the diastereofacial selectivities in the formation of the adducts were determined by NMR spectroscopy and by chemical transformations. The quantitative distribution of adducts as a function of stereochemistry of the dienophile is discussed.

Cycloaddition of cyclopentadiene with a d -arabinose-derived cis -dienophile, methyl ( Z )-4,5,6,7-tetra- O -acetyl-2,32-dideoxy- d - arabino -hept-2-enonate ( 2 ), under thermal conditions gave essentially a single norbornene aduct, isolated crystaline in 81% yield and identified by NMR spectroscopy and X-ray crystallography as methyl ( 5R ,6S)-6- endo -(1,2,3,4-tetra- O -acetyl- d - arabino -tetritol-1-yl) bicyclo[2.2.1]-hept-2-ene-5- endo -carboxylate ( 3 ). The diene adds exclusively from the si -face of the dienophile and give only the endo product. The same sequence starting from l -arabinose gave the enantiomer ( 7 ) of 3 . In contrast, a related cis -dienophile ( 9 ) having a butenolide ring with cyclopentadiene from the opposite ( re ) face giving mainly the endo adduct (5S,6R)-6- endo -(2,3,4-tri- O -acetyl)- d - arabino -tetritol-1-yl) bicyclo[2.2.1]hept-2-ene-5- endo -carboxylic acid 1,4-lactone ( 10 ), isolated crystalline in 70% yield, whose structure was again established by NMR spectroscopy, and firmly consolidated by X-ray crystallography. The minor (11%) product was the exo (5S,6R)isomer 11 . A cis -enonate 14 , analogous to 2 but deoxygenated at the allylic position, showed negligible diastereofacial selectivity ans reacted with cyclopentadiene to give a mixture of all four possible adducts. A 6-membered ring dienophile 16 was also subjected to the same cycloaddition for comparison with the butenolide 9 ; it gave principally the two endo products 17 and 19 in 31 and 38% yields, respectively, accompanied by 12% of a mixture of the two exo products ( 18 and 20 ). The quantitative distribution of cycloaddition products as a function of dienophile stereochemistry is discussed. The high degree of asymmetric induction observed, especially with the readily accesible dienophiles 2 and 7 , providesa valuable route of access to enantiomerically pure tetra- C -substituted cycloalkanes.

The title glycoside undergoes acetonation with 2-methoxypropene to give a 2:1 mixture of the crystalline 2,3- and 3,4-isopropylidene acetals in 94% yield, which upon methylation under controlled conditions followed by deacetonation afforded the respective 4- and 2-monomethyl ethers. The 2,3-acetal underwent reaction with diethylaminosulfur trifluoride to introduce fluorine at C-4 with net retention of stereochemistry, but the 3,4-acetal under comparable conditions underwent migration of the arylthio group to C-2 and fluorination at C-1, with stereochemical retention at both positions.

A convenient preparative route is described for 3-deoxyaldulosonic acids. Glycal precursors are oxidatively converted into 2-deoxyaldonolactones, which react with 1,3-dithian-2-yl anion to afford 1,3-propanediyl dithioacetals of higher 3-deoxyaldosuloses. Deprotection with mercuric salts in wet or dry alcohols gave high yields of the corresponding alkyl aldulosonates. Preparative reaction conditions were optimized and the anomeric configurations of the ketopyranose products were established by 13C NMR.

The chiral norbornene derivative 2 obtained from Lewis acid-catalyzed reaction of an l -arabinose-derived dienophile 1 and cyclopentadiene was oxidized with OsO 4 NaIO 4 to the dialdehyde 3 , a tetrasubstituted cyclopentane. Mild treatment of 3 with [Rh(dppp) 2 ]Cl (dppp = Ph 2 P(CH 2 ) 3 PPh 2 ] ( 4 selectively epimerized the aldehyde adjacent to the methoxycarbonyl group to give the epi-aldehyde 8 . Under more vigorous conditions, this group was decarbonylated to give the monoaldehyde 11 , and more strenuous treatment removed the second aldehyde group to give the didecarbonylated cyclopentane derivative 5 . The structure and optical purity of 5 was confirmed by its transformation into (1 S ,2 S )-cyclopentane-1,2-dicarboxylic acid ( 7 ).

The C 7 acyclic unsaturated-sugar ester 1 , derived from l -arabinose, and its enantiomer serve as convenient dieneophiles for chirality transfer for synthesis of optically pure carbocyclic derivatives through cycloaddition reactions. Reaction of 1 with cyclopentadiene may be controlled to give preparative access to the 5,6-disubstituted norbornene adducts 4a , 5a , and 7a , according to the conditions used. The distribution of the four possible isomeric products from this cycloaddition was quantitated, and the effect of substitutional variation on the precursor dienophile 1 was also examined. Adducts 4a and 5a were transformed into such substituted carbocycles of known absolute configuration as the methyl esters ( 11 and 12 ) of norbornene (bicyclo[2.2.1]hept-2-ene)-6-carboxylic acid and nortricyclane (tricyclo[2.2.1.0 2,6 ]heptane)-3-carboxylic acid in optically pure form, specifically through decarbonylation reactions using RhCl(PPh 3 ) 3 (Wilkinson's complex) and [Rh(dppp) 2 ]Cl[dppp = Ph 2 P(CH 2 ) 3 PPh 2 ]. The optical purity of 12 was established by the use of a chiral lanthanide shift-reagent.

Cyclopentadiene reacts with a D-glucose-derived hex-3-enose derivative to give norbornene derivatives attached at the 2,3-position of a 1,6-anhydrohexose skeleton; although the bicyclic enone isolevoglucosenone is a plausible intermediate in this reaction, the products actually appear to arise through initial cycloaddition to a rearranged acyclic sugar derivative with subsequent generation of the anhydro ring.

A set of cis -dienophiles ( 2, 6, 9 ) derived from D - or L -arabinose reacts with high yield and stereospecificity to give enantiomerically pure 5,6-disubstituted norbornenes.

Each of the four d -aldopentoses (1–4) reacts in the unprotected form with Ph3PCHCO2Me (5) in THF to give stereoslectively the coresponding trans-α,β-unsaturated C7 Wittig adducts, isolated as the corresponding 4,5,6,7-tetraacetates (7–10) or 4,5:6,7-di-O-isopropylidene derivatives (11–14). Concurrently formed are also bicyclic, 1,4-lactone derivatives, isolated as their 5,7-diacetates (15–18) or 5,7-O-isopropylidene derivatives (19), arising through intramolecular Michael addition from the initial acyclic adducts. Formation of the cyclized products is suppressed by incorporation of Cu(OAc)2 in the reaction mixture, permitting preparative isolation of the hept-3-enonate derivatives 7–10, useful as dienophiles in Diels-Alder carbocyclizations with chirality transfer. Optimized yields were 25% ( d -ribo), 50% ( d -arabino), 49% ( d -xylo), and 61% ( d -lyxo). Under Cu(OAc)2-catalyzed conditions, the formation of small proportions of 3,7-anhydroheptonic acid esters (21 and 23) was observed in the d -arabino and d -xylo series, but not with the other two pentoses.

Cycloaddition of cyclopentadiene with a d -arabinose-derived cis -dienophile, methyl ( Z )-4,5,6,7-tetra- O -acetyl-2,32-dideoxy- d - arabino -hept-2-enonate ( 2 ), under thermal conditions gave essentially a single norbornene aduct, isolated crystaline in 81% yield and identified by NMR spectroscopy and X-ray crystallography as methyl ( 5R ,6S)-6- endo -(1,2,3,4-tetra- O -acetyl- d - arabino -tetritol-1-yl) bicyclo[2.2.1]-hept-2-ene-5- endo -carboxylate ( 3 ). The diene adds exclusively from the si -face of the dienophile and give only the endo product. The same sequence starting from l -arabinose gave the enantiomer ( 7 ) of 3 . In contrast, a related cis -dienophile ( 9 ) having a butenolide ring with cyclopentadiene from the opposite ( re ) face giving mainly the endo adduct (5S,6R)-6- endo -(2,3,4-tri- O -acetyl)- d - arabino -tetritol-1-yl) bicyclo[2.2.1]hept-2-ene-5- endo -carboxylic acid 1,4-lactone ( 10 ), isolated crystalline in 70% yield, whose structure was again established by NMR spectroscopy, and firmly consolidated by X-ray crystallography. The minor (11%) product was the exo (5S,6R)isomer 11 . A cis -enonate 14 , analogous to 2 but deoxygenated at the allylic position, showed negligible diastereofacial selectivity ans reacted with cyclopentadiene to give a mixture of all four possible adducts. A 6-membered ring dienophile 16 was also subjected to the same cycloaddition for comparison with the butenolide 9 ; it gave principally the two endo products 17 and 19 in 31 and 38% yields, respectively, accompanied by 12% of a mixture of the two exo products ( 18 and 20 ). The quantitative distribution of cycloaddition products as a function of dienophile stereochemistry is discussed. The high degree of asymmetric induction observed, especially with the readily accesible dienophiles 2 and 7 , providesa valuable route of access to enantiomerically pure tetra- C -substituted cycloalkanes.

Summary 5-Azido-2,3,4-tri-O-benzoyl-5-deoxy-D-xylose diethyl dithioacetal (3) undergoes smooth Lewis acid-catalyzed demercaptalation (boron trifluoride etherate/HgO) to afford the unstable aldehydo-azide 4, which in the presence of Lewis acids yields the tribenzoate 6 of the title compound (7) via an apparent intramolecular Schmidt rearrangement.

Two unrelated molecules of the title compound, ethyl 1-(5-deoxy-1,2-O-isopropylidene-alpha-D-xylofuranos-5-C- yl)-1,2,3-triazole-5-carboxylate, C13H19N3O6, that are not linked by hydrogen bonding, comprise the asymmetric unit. There are no unusual bond lengths or angles. The two molecules differ in the degree of rotation around the methylene C atom that joins the triazole ring to the sugar part of the molecule. Molecules of the same conformation form infinite chains joined by hydrogen bonding between a H atom on the hydroxyl group of one molecule and an N atom in the triazole ring of another molecule generated by the 2(1) screw axis. Relevant intermolecular N...O distances are 3.013 (3) and 2.806 (3) A.

Preparative routes for anomerically specific 1- C -allylation of 2-amino-2-deoxy sugars have been evaluated in a comparative study of various N -substituents and aglycons as precursors for glycosyl radicals that effectively capture an allyl group from allyltributyltin. The crystalline triacetate 4 of 3-(2-acetamido-2-deoxy- α - d -glucopyranosyl)-1-propene ( 6 ) was obtained in 70% yield when 2-acetamido-3,4,6-tri- O -acetyl-2-deoxy- α - d -glucopyranosyl chloride ( 1 ) was treated with allyltributyltin under free-radical conditions, whereas the corresponding bromide 3 led only to an oxazolidine derivative; the β -1-ethylxanthate analogue of 1 gave 4 , but in only 25% yield. The 2-trifluoroacetamido 1-bromide analogue of 1 was also an effective radical source, giving the 2-trifluoroacetamido analogue 8 of 4 in 60% yield. The free amino analogue 7 of 4 was conveniently obtained via the 2- p -methoxybenzylideneamino 1-bromide analogue of 1 . Use of 3,4,6-tri- O -acetyl-2-deoxy-2-phthalimido- β - d -glucopyranosyl bromide as radical precursor allowed stereospecific access to β -1- C -allyl derivatives of the amino sugar. The crystalline galactosamine analogue 12 of 4 was obtained by using the galacto analogue of chloride 1 , but the corresponding manno chloride gave only an oxazoline product. The 1- C -allylated amino sugar derivatives are conformationally more mobile than derivatives not having a 1- C -linked substituent.

The title dithioxyloside 1 , an orally active antithrombotic agent, as its 2,3-isopropylidene acetal, was converted into the corresponding glycos-4-ulose, which served as precursor via reduction to the 4-epimer of 1 and via oximation–reduction to the 4-acetamido-4-deoxy 4-epimer of 1 .

The 4,6-benzylidene acetal of methyl 2-deoxy-2-fluoro-α,β- d -glucopyranoside underwent inversion at C-3 via an oxidation–reduction sequence, and treatment of the derived 3-acetate with N -bromosuccinimide in carbon tetrachloride gave methyl 3- O -acetyl-4- O -benzoyl-6-bromo-2,6-dideoxy-2-fluoro-α- d -allopyranoside ( 6 ). Dehydrobromination of 6 and reduction of the resultant 5,6-ene gave the 5-epimer of 6 , which after removal of the ester substituents, afforded the title compound in good overall yield.

Based on a literature precedent, preparation of methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-mannopyranoside (18) was attempted via fluorination of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-altropyranoside with diethylaminosulfur trifluoride (DAST). Contrary to expectations, the reaction took place with retention of configuration at the site of the fluorination yielding methyl 4-azido-2-O-benzyl-3,4,6-trideoxy-3-fluoro-alpha-D-altropyranoside. Treatment with DAST of methyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-allopyranoside (8), or its 2-(p-methoxybenzyl) analog 9 resulted in fluorination with inversion of configuration at position 3, to give the corresponding 3-deoxy-3-fluoro glucopyranosides 10 and 11, respectively. Accordingly, compound 18 was prepared from 11, by de-p-methoxybenzylation at O-2, followed by inversion of configuration at C-2 in the resulting methyl 4-azido-3,4,6-trideoxy-3-fluoro-alpha-D-glucopyranoside. The 2-O-methyl analog of 18 (19) was prepared by methylation of 18. Compounds 18 and 19 were converted, conventionally, into the 3-fluoro analogs of the terminal determinants of the O-PS of Vibrio cholerae O:1, serotype Inaba and Ogawa, respectively.

The C 7 acyclic unsaturated-sugar ester 1 , derived from l -arabinose, and its enantiomer serve as convenient dieneophiles for chirality transfer for synthesis of optically pure carbocyclic derivatives through cycloaddition reactions. Reaction of 1 with cyclopentadiene may be controlled to give preparative access to the 5,6-disubstituted norbornene adducts 4a , 5a , and 7a , according to the conditions used. The distribution of the four possible isomeric products from this cycloaddition was quantitated, and the effect of substitutional variation on the precursor dienophile 1 was also examined. Adducts 4a and 5a were transformed into such substituted carbocycles of known absolute configuration as the methyl esters ( 11 and 12 ) of norbornene (bicyclo[2.2.1]hept-2-ene)-6-carboxylic acid and nortricyclane (tricyclo[2.2.1.0 2,6 ]heptane)-3-carboxylic acid in optically pure form, specifically through decarbonylation reactions using RhCl(PPh 3 ) 3 (Wilkinson's complex) and [Rh(dppp) 2 ]Cl[dppp = Ph 2 P(CH 2 ) 3 PPh 2 ]. The optical purity of 12 was established by the use of a chiral lanthanide shift-reagent.

d -Lyxose ( 1 ) undergoes acetonation under kinetic conditions with 2-methoxypropene to give 2,3- O -isopropylidene-α- d -lyxofuranose ( 2 ) in high yield, further characterized as its 1,5-diacetate 3 , thus affording a preparative route to 2 . Forcing conditions are required to bring d -xylose ( 5 ) into reaction, leading to 39% of 3,5- O -isopropylidene-α-β- d -xylofuranose ( 7 , further characterized as its 1,2-diacetate 9 ), 33% of 1,2:3,5-di- O -isopropylidene-α- d -xylofuranose ( 6 ), and 20% of 2,3:4,5-di- O -isopropylidene- aldehydo - d -xylose ( 8 , further characterized as its aldehydrol diacetate 10 ). The results are all readily rationalized within the framework of the general principles earlier advanced for kinetic acetonation of sugars.

Exclusive trans -addition is observed in the iodoalkoxylation of the 6-membered cyclic enol ethers 3,4-di- O -acetyl- l -rhamnal ( 1 ), 3,4-di- O -acetyl- l -fucal ( 2 ), and related glycal derivatives. The main products from 1 and from 3,4,6-tri- O -acetyl- d -glucal ( 3 ) thus had the α- manno configuration. Similarly, α- talo products were obtained from 2 in 87–93% yield. The product distribution is not affected by the electronegativity of the 5-substituent. It is concluded that steric factors in the glycal and the nucleophile affect only the step of trans -diaxial opening of the intermediate iodonium ion. Enhanced yields of the desired trans -diaxial products were observed in reactions of glycals having the lyxo configuration when the reactions were conducted in tetrahydrofuran or methanol.

The scope and limitations of radical-mediated 3′-C-substitution of pyrimidine nucleosides was evaluated with 5′- O -( tert -butyldimethylsilyl)thymidine or its tert -butyldiphenylsilyl analogue having thionoester or thionoamide groups at O-3′, including (methylthio)thiocarbonyl, (phenoxy)thiocarbonyl, (pentafluorophenoxy)thiocarbonyl, and (1-imidazolyl)thiocarbonyl. Their reaction with acrylonitrile, methyl acrylate, and allyltributyltin under radical-generating conditions affords corresponding 3′-C-alkylated products, together with the product of simple deoxygenation at C-3′. The conditions for optimizing the yield of 3′-C-substituted product are presented.

Acetylation of the 2,3-O-isopropylidene derivative (1) of D-glyceraldehyde with hot acetic anhydride in the presence of sodium acetate give a mixture of (Z)- and (E)-enol acetates (2 and 3), together with the acetylated racemic aldehydrol (4) of 1. Likewise, the acyclic aldehydo 2,3:4,5-diisopropylidene acetals of D- and L-arabinose, D-xylose, and D-ribose underwent conversion into enol acetates, with the (Z) isomers preponderating, and convertible photochemically into the corresponding (E) isomers. Under other conditions of acetylation, the aldehydo derivatives were converted into the corresponding aldehydrol diacetates.

Mercuric-ion promoted condensation of 6-chloropurine with acetylated dimethyl dithioacetals of D-ribose and D-arabinose in nitromethane afforded a separable mixture of 1'(S)-2,3,4,5-tetra-O-acetyl-1-(6-chloropurin-9-yl)-1-S-methyl-1-thio-D-ribitol (4) and its 1'(R) diastereomer, and the corresponding 1'(R)-arabinitol analogue (5); the structure of 4 was confirmed by X-ray crystallography. Desulfurization of 4 and 5 by tributylstannane in toluene gave 2,3,4,5-tetra-O-acetyl-1-(6-chloropurin-9-yl)-1-deoxy-D-ribitol (7) and the arabinitol analogue 8, convertible by the action of thiourea into the 1,6-dihydro-6-thioxopurin-9-yl analogues 9 and 10, which on deacetylation furnished the corresponding acyclic-sugar nucleosides 11 and 12.

Two unrelated molecules of the title compound, ethyl 1-(5-deoxy-1,2-O-isopropylidene-alpha-D-xylofuranos-5-C- yl)-1,2,3-triazole-5-carboxylate, C13H19N3O6, that are not linked by hydrogen bonding, comprise the asymmetric unit. There are no unusual bond lengths or angles. The two molecules differ in the degree of rotation around the methylene C atom that joins the triazole ring to the sugar part of the molecule. Molecules of the same conformation form infinite chains joined by hydrogen bonding between a H atom on the hydroxyl group of one molecule and an N atom in the triazole ring of another molecule generated by the 2(1) screw axis. Relevant intermolecular N...O distances are 3.013 (3) and 2.806 (3) A.

Each of the four d -aldopentoses (1–4) reacts in the unprotected form with Ph3PCHCO2Me (5) in THF to give stereoslectively the coresponding trans-α,β-unsaturated C7 Wittig adducts, isolated as the corresponding 4,5,6,7-tetraacetates (7–10) or 4,5:6,7-di-O-isopropylidene derivatives (11–14). Concurrently formed are also bicyclic, 1,4-lactone derivatives, isolated as their 5,7-diacetates (15–18) or 5,7-O-isopropylidene derivatives (19), arising through intramolecular Michael addition from the initial acyclic adducts. Formation of the cyclized products is suppressed by incorporation of Cu(OAc)2 in the reaction mixture, permitting preparative isolation of the hept-3-enonate derivatives 7–10, useful as dienophiles in Diels-Alder carbocyclizations with chirality transfer. Optimized yields were 25% ( d -ribo), 50% ( d -arabino), 49% ( d -xylo), and 61% ( d -lyxo). Under Cu(OAc)2-catalyzed conditions, the formation of small proportions of 3,7-anhydroheptonic acid esters (21 and 23) was observed in the d -arabino and d -xylo series, but not with the other two pentoses.

The chiral norbornene derivative 2 obtained from Lewis acid-catalyzed reaction of an l -arabinose-derived dienophile 1 and cyclopentadiene was oxidized with OsO 4 NaIO 4 to the dialdehyde 3 , a tetrasubstituted cyclopentane. Mild treatment of 3 with [Rh(dppp) 2 ]Cl (dppp = Ph 2 P(CH 2 ) 3 PPh 2 ] ( 4 selectively epimerized the aldehyde adjacent to the methoxycarbonyl group to give the epi-aldehyde 8 . Under more vigorous conditions, this group was decarbonylated to give the monoaldehyde 11 , and more strenuous treatment removed the second aldehyde group to give the didecarbonylated cyclopentane derivative 5 . The structure and optical purity of 5 was confirmed by its transformation into (1 S ,2 S )-cyclopentane-1,2-dicarboxylic acid ( 7 ).