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The synthesis and biological evaluation of some new glycose esters bearing the 1,2- O -isopropylidene- d -hexofuranose functionality and belonging to the 3- O -acyl- d -allose and 6- O -acyl- d -glucose series are reported. When the results concerning cell growth inhibition are compared, it appears that the 6- O -acyl- d -glucose derivatives are more active than the 3- O -acyl- d -allose compounds. Within both 6- O -acyl- d -glucose and 3- O -acyl- d -allose derivatives, butyric esters displayed the highest inhibitory effects. Inhibition of cell growth is not associated with high induction levels of erythroid differentiation, despite the fact that pivaloates induce erythroid differentiation to an extent similar to that exhibited by previously reported molecules [ Bioorg. Med. Chem. Lett. 1999 , 9 , 3153–3158].

Replacement of specific hydroxyl groups by fluorine in carbohydrates is an ongoing challenge from chemical, biological, and pharmaceutical points of view. A rapid and efficient two-step, regio- and stereoselective synthesis of 2-deoxy-2-(R)-fluoro-beta-d-allose (2-(R)-fluoro-2-deoxy-beta-d-allose; 2-FDbetaA), a fluorinated analogue of the rare sugar, d-allose, is described. TAG (3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxy-d-arabino-hex-1-enitol or 3,4,6-tri-O-acetyl-d-glucal), was fluorinated in anhydrous HF with dilute F(2) in a Ne/He mixture or with CH(3)COOF at -60 degrees C. The fluorinated intermediate was hydrolyzed in 1N HCl and the hydrolysis product was purified by liquid chromatography and characterized by 1D (1)H, (13)C, and (19)F NMR spectroscopy as well as 2D NMR spectroscopy and mass spectrometry. In addition, (18)F-labeled 2-deoxy-2-(R)-fluoro-beta-d-allose (2-[(18)F]FDbetaA) was synthesized for the first time, with an overall decay-corrected radiochemical yield of 33+/-3% with respect to [(18)F]F(2), the highest radiochemical yield achieved to date for electrophilic fluorination of TAG. The rapid and high radiochemical yield synthesis of 2-[(18)F]FDbetaA has potential as a probe for the bioactivity of d-allose.

D-allose, an all-cis aldo-hexose, is non-caloric and possesses antioxidant properties. We investigated the effects of oral D-allose supplementation on the development of high blood pressure and the oxidative status in two genetically hypertensive animal models: Dahl salt-sensitive hypertensive (DS) rats and spontaneously hypertensive rats.The systolic blood pressure of DS rats fed a 4% salt diet for 4 weeks significantly increased from 122+/-8 to 161+/-5 mmHg as compared with DS rats fed a normal salt diet (138+/-5 mmHg at 4 weeks), whereas concordant supplementation of D-allose, but not D-glucose, with a dose of 2 g/kg daily to salt-loaded DS rats suppressed the development of high blood pressure (135+/-7 mmHg at 4 weeks), accompanied with decreases in superoxide production in the aorta that was determined by the lucigenin chemiluminescence and dihydroethidium staining. The increases of urinary protein secretion of salt-loaded DS rats were prevented by D-allose supplementation (DS rats fed 0.5% salt, 18.2+/-6.3 mg/day; DS rats fed 4% salt alone, 81.8+/-16.5 mg/day; DS rats fed 4% salt+D-allose, 31.3+/-11.8 mg/day; DS rats fed 4% salt+D-glucose, 85.3+/-20.5 mg/day). On the other hand, D-allose supplementation in spontaneously hypertensive rats had no significant effect on the blood pressure or the aortic superoxide production during the early developing stage of hypertension.These results underscore the role of enhanced oxidative stress in the pathogenesis of high blood pressure development in DS rats, and suggest the possibility of D-allose supplementation for prevention of salt-sensitive hypertension.

A recombinant thermophilic Thermus caldophilus GK24 hexokinase, one of the ROK-type (repressor protein, open reading frames, and sugar kinase) proteins, exists uniquely as a 120 kDa molecule with four subunits (31 kDa), in contrast to eukaryotic and bacterial sugar kinases which are monomers or dimers. The optimal temperature and pH for the enzyme reaction are 70–80 °C and 7.5, respectively. This enzyme shows broad specificity toward glucose, mannose, glucosamine, allose, 2-deoxyglucose, and fructose. To understand the sugar specificity at a structural level, the enzyme–ATP/Mg 2+ –sugar binding complex models have been constructed. It has been shown that the sugar specificity is probably dependent on the interaction energy occurred by the positional proximity of sugars bound in the active site of the enzyme, which exhibits a tolerance to modification at C2 or C3 of glucose.

Mycosamine is a dideoxyaminosugar found in medicinally relevant macrolides, including amphotericin B and nystatin. Herein we report a reliable, high yielding, scalable synthesis of a mycosamine donor. A major goal of our approach was to minimize purifications via judicious selection of protecting groups; the inherent properties of the allose framework created some deprotection obstacles that were ultimately solved.

Vibrational circular dichroism (VCD) spectra in the entire 2000-900 cm(-1) region have been recorded, for the first time, for films of carbohydrates prepared from aqueous solutions. Eight different carbohydrates, alpha-D-glucopyranosyl-(1--4)-D-glucose, cyclomaltohexaose, alpha-D-glucopyranosyl alpha-D-glucopyranoside, beta-D-glucopyranosyl-(1--6)-D-glucose, beta-D-glucopyranosyl-(1--4)-D-glucose, D-glucose, and both enantiomers of 6-deoxygalactose and of allose, were investigated. The VCD spectra obtained for films are found to be identical to the corresponding spectra obtained for aqueous solutions of carbohydrates. These measurements demonstrate several advantages of significant importance. The strong infrared absorption of water has prevented, in the past, the pursuit for routine applications of VCD in determining the structures of carbohydrates in aqueous solutions. This limitation is not present for film studies because water solvent is removed in the process of preparing the films. Also, strong infrared absorption of water at 1650 cm(-1) requires the use of very short-pathlength (6 microm) cells for measurements on aqueous solutions. This requirement and concomitant inconveniences (such as laborious assembling of a demountable liquid cell or purchasing an expensive variable pathlength liquid cell) have been eliminated for film measurements. The removal of interfering water absorption in film studies resulted in higher light throughput and better signal-to-noise ratios for VCD measurements. Another point of significance is that the amount of carbohydrate sample required for VCD measurements on films is approximately one to two orders of magnitude smaller than that required for corresponding VCD measurements on aqueous solutions. Since carbohydrate samples can now be studied as films, VCD spectroscopy becomes much more broadly applicable for carbohydrates than previously believed. The present work, in combination with other film measurements in our laboratory, indicate that VCD studies on films can be used more generally, providing a convenient and powerful approach for probing structural information for biologically important compounds.

Studies of carbohydrates have been hampered by the lack of chemical strategies for the expeditious construction and coupling of differentially protected monosaccharides. Here, a synthetic route based on aldol coupling of three aldehydes is presented for the de novo production of polyol differentiated hexoses in only two chemical steps. The dimerization of α-oxyaldehydes, catalyzed by l -proline, is then followed by a tandem Mukaiyama aldol addition-cyclization step catalyzed by a Lewis acid. Differentially protected glucose, allose, and mannose stereoisomers can each be selected, in high yield and stereochemical purity, simply by changing the solvent and Lewis acid used. The reaction sequence also efficiently produces 13 C-labeled analogs, as well as structural variants such as 2-amino– and 2-thio–substituted derivatives.

6,6′-Linked ethers derived from D-allose, D-galactose, D-glucose, and D-mannose have been prepared in order to allow comparisons with the reported 6,6′-linked hexopyranose coyolosa, an hypoglycemic compound which has been isolated by extraction of the root of the palm Acrocomia mexicana. Comparison of NMR data from the ethers and their derived peracetates with corresponding reported data from coyolosa and its peracetate indicate that coyolosa is not a 6,6′-linked disaccharide. The synthesised compounds are representatives of a novel class of disaccharide derivatives which are linked tail to tail in contrast to the more usual head to tail (e.g. maltose) or head to head (e.g. trehalose) disaccharides.

The crystal structure of a new polymorph, Form II, of β-D-allose has been determined by X-ray powder diffraction. The unit cell is hexagonal, a = b = 16.598 A, c = 4.856 A, α = β = 90°, γ = 120°, space group P62 with Z = 6, Z′ = 1. The molecule adopts the 4C1 chair-conformation, with a torsional change of conformation of the O6 side-chain compared to the orthorhombic Form I. The two polymorphs share a common feature of a stacked hydrogen bonded column of molecules in the short axis direction. The structures differ in hydrogen linking of these columns. The more stable Form I has more immediate neighbours linked by hydrogen bonds to a reference molecule, and higher crystal density than Form II.

The C‐glycoside of methyl α‐d‐altropyranosyl‐(1→4)‐α‐d‐glucopyranoside 2 was prepared in a convergent fashion, from readily available precursors, 4‐O‐tert‐butyldiphenylsilyl‐1,2‐O‐isopropylidene‐d‐erythro‐S‐phenyl monothiohemiacetal 13 (five steps from D‐ribose) and the known acid, methyl 2,3,6‐tri‐O‐benzyl‐4‐C‐(carboxymethyl)‐4‐deoxy‐α‐d‐glucopyranoside 17 (seven steps from methyl α‐d‐glucopyranoside). The key reactions in the synthesis are the oxocarbenium ion cyclization of thioacetal‐enol ether 19 to a C1 substituted glycal 20, and the stereoselective hydroboration of 20 to the α‐C‐altroside 21. †This paper is Dedicated to Professor Gerard Decotes on the occasion of his 70th birthday.

The title compound, C6H12O6, a C-3 position epimer of glucose, was crystallized from an equimolar mixture of D- and L-allose. It was confirmed that D-allose (L-allose) formed β-pyranose with a4C1(1C4) conformation in the crystal. In the crystal, molecules are linked by O—H...O hydrogen bond, forming a three-dimensional framework. The cell volume of the racemic β-D,L-allose is 739.36 (3) Å3, which is about 10 Å3smaller than that of chiral β-D-allose [V= 751.0 (2) Å3].

The analysis of the polar fraction of Melittis melissophyllum L. subsp. melissophyllum led to the identification of several iridoid glycosides: monomelittoside (1), melittoside (2), harpagide (3), acetyl-harpagide (4) and ajugoside (5). Compounds 3 and 4 are considered marker compounds for the genus and, as well as compounds 1, 2 and 5, were already evidenced in a previous study on the nominal species. It was noteworthy of the presence of allobetonicoside (6) which was never reported for this genus. The isolation of 6 is very relevant because of its allose residue on the structure. Allose has been often found in the species of the subfamily Lamioideae even if it mostly regarded flavonoids considered of chemotaxonomical relevance for some correlated genera of Lamiaceae. Same as allosyl-glycosidic flavonoids, the presence of allosyl-glycosidic iridoids may also be an additional chemosystematic evidence of botanical relationships among Lamiaceae species and genera.

1-(Z)-Alkoxy-4-(E)-methoxybutadiene derivatives have been reacted with ethylgyoxylate and diethyl ketomalonate under thermal or hyperbaric conditions. They provide, with a total regioselectivity and fair to total endoselectivities, the expected dihydropyranic cycloadducts. Three of those pseudo-glycals have been converted in a few classical steps (deprotection, reduction, and dihydroxylation) into (racemic) allose, mannose, and gullose derivatives. The order of these three steps has a direct influence on the efficiency of the transformation and determines the stereochemistry of the final sugar.

Conformational changes of periplasmic binding proteins are essential for their function in chemotaxis and transport. The allose-binding protein from Escherichia coli is, like other receptors in its family, composed of two α/β domains joined by a three-stranded hinge. In the previously determined structure of the closed, ligand-bound form (Chaudhuri, B. N., Ko, J., Park, C., Jones, T. A., and Mowbray, S. L. (1999) J. Mol. Biol. 286, 1519–1531), the ligand-binding site is buried between the two domains. We report here the structures of three distinct open, ligand-free forms of this receptor, one solved at 3.1-A resolution and two others at 1.7-A resolution. Together, these allow a description of the conformational changes associated with ligand binding. A few large, coupled torsional changes in the hinge strands are sufficient to generate the overall bending motion, with only minor disruption of the individual domains. Integral water molecules appear to act as structural “ball bearings” in this process. The conformational changes of the related ribose-binding protein follow a distinct pattern. The observed differences between the two proteins can be interpreted in the context of changes in sequence and in crystal packing and provide new insights into the nature of hinge bending motion in this class of periplasmic binding proteins.

A stereodivergent entry to 5a-carba-D- and L-pyranoses from a single precursor is described. The approach is based on the selective deoxygenation of polyoxygenated methylcyclohexane intermediates, readily available from radical cyclization of D-mannose derivatives. This strategy has been applied to the preparation of 5a-carba-α-D-allo-, 5a-carba-β-L-talo-, and 5a-carba-α-L-gulopyranose pentaacetates.

Thirteen glycosides and methyl (3R,5R)-5-hydroxy-(beta-D-glucopyranosyloxy)-hexanoate were newly isolated from the Japanese fern Hymenophyllum barbatum, although our previous work revealed the isolation of hemiterpene glycosides, hymenosides A-J, from the same species. The structures of the newly isolated glycosides were elucidated by extensive two-dimensional (2D) NMR and/or chemical evidence. The structures of those aglycones were divided into four types, 2-methyl-but-2-ene-1,4-diol, 2-hydroxymethyl-but-2-ene-1,4-diol, 2-methylene-butane-1,3,4-triol, and 3-hydroxy-5-hexanolide. The sugar moieties, which were acylated by phenylacetic acid derivatives, were also established by chemical and spectroscopic methods. Eight glucosides of the isolated compounds in the present investigation had a bitter or weakly pungent taste. It is clear that a phenylacetyl group attached to glucose or allose as an ester is necessary for the bitter taste.

The first analytical method is presented for the identification and absolute configuration determination of all 24 aldohexose and 2-ketohexose isomers, including the D and L enantiomers for allose, altrose, galactose, glucose, gulose, idose, mannose, talose, fructose, psicose, sorbose, and tagatose. Two unique fixed ligand kinetic method combinations were discovered to create significant enough energetic differences to achieve chiral discrimination among all 24 hexoses. Each of these 24 hexoses yields unique ratios of a specific pair of fragment ions that allows for simultaneous determination of identification and absolute configuration. This mass spectrometric-based methodology can be readily employed for accurate identification of any isolated monosaccharide from an unknown biological source. This work provides a key step towards the goal of complete de novo carbohydrate analysis.

The synthesis of 2,3-epoxyamide derivatives of 2-amino-2-deoxy- d -allose is described. Epoxidation of the corresponding α,β-unsaturated amides with m -CPBA took place with better stereoselectivity when an oxazolidine ring was fused to the 2,3-positions of the sugar molecule. In most cases, both stereoisomers could be isolated and characterized. The stereochemistry of the new stereogenic centers was then determined by cleavage of the oxirane moiety from the chiral auxiliary, which was also recovered.

Pyrimidine 1′-aza-C-nucleosides are synthesised by the fusion of 5-bromouracil, 5-bromocytosine and 5-bromoisocytosine with (3R,4R)-4-(hydroxymethyl)pyrrolidin-3-ol in 40–41% yield. A homologue of 1′-aza-Ψ-uridine is obtained in a Mannich reaction in 65% yield by treatment of the azasugar, paraformaldehyde and uracil. N-Alkylation of (3R,4R)-4-(hydroxymethyl)pyrrolidin-3-ol with 6-chloromethyluracil gives the 6-regioisomeric homologue. (3R,4R)-4-(Hydroxymethyl)pyrrolidin-3-ol is synthesised in 25% overall yield from diacetone- d -glucose via 3-C-(azidomethyl)-3-deoxy- d -allose which is subjected to an intramolecular reductive amino alkylation reaction to give (3R,4S)-4-[(1S,2R)-1,2,3-trihydroxypropyl]pyrrolidin-3-ol followed by Fmoc protection, oxidative cleavage of the triol group with further reduction of the obtained aldehyde and subsequent deprotection of the nitrogen atom.

Intramolecular 1,3-dipolar cycloadditions of nitrones formed from 3-O-allyl- d -glucose and d -altrose (both with threo-configuration at C-2,3) afford oxepanes selectively whereas the same reactions of nitrones derived from 3-O-allyl- d -allose and d -mannose (both with erythro-configuration at C-2,3) give tetrahydropyrans selectively.

The synthesis of 3-spirohydantoin derivatives of d -allose and d -ribose is reported. The key step is the stereoselective conversion of glyco-α-aminonitriles from ulose derivatives of d -glucose and d -xylose using titanium(IV) isopropoxide as a mild and efficient catalyst. Cyclisation of the glyco-α-aminonitriles give the target spirohydantoins.

The use of 2-amino-2-deoxy- d -allose in the synthesis of oxazolidines is described. The reaction takes place with total stereoselectivity in the preparation of both simple oxazolidines (from aldehydes as reagent) and bicyclic oxazolidines (from chlorocarbonyl compounds and keto-acids as reagents). The reactivity of the obtained oxazolidines with hydride and alkylmagnesium chlorides is also described.

A novel diaza-18-crown-6-based saccharide receptor (4) bearing two boronic acid groups has been developed. In 4 boronic acid groups in the side arms interact as Lewis acids with amines and boron atoms are changed to sp3 hybridization through the B···N interaction. Because of this hybridization, the boronic acid groups can bind saccharides even in a neutral pH region. Judging from the distance between two boronic acid groups in 4 assuming a syn conformation, one can expect that 4 forms 1:1 cyclic complexes with monosaccharides. These are confirmed by circular dichroism spectroscopy of 4 in the presence of glucose and allose. UV photometric titration studies showed that the boronic acid groups and metal cation bound to the crown cavity competitively interact as Lewis acids with the crown amines. As a result, saccharides and metal cations “communicate” with each other in an allosteric manner. It was shown that added metal cations can affect the saccharide binding ability of 4 through the competitive interact...

The phosphorylation reaction by inorganic cyclo -triphosphate (P 3m ) having a six-membered ring was examined for d -aldohexoses and d -aldopentoses in aqueous solution. Similar to the process for d -glucose, d -galactose, d -xylose or d -allose were phosphorylated with P 3m to give stereoselectively β- d -galactopyranosyl 1-triphosphate, β- d -xylopyranosyl 1-triphosphate or β- d -allopyranosyl 1-triphosphate with maximum yields of 31.3, 32.5 or 32.1%, respectively. On the other hand, in the reaction of d -ribose, d -lyxose, d -mannose or d -arabinose with P 3m , the yields of β- d -ribopyranosyl 1-triphosphate, α- d -lyxopyranosyl 1-triphosphate, α- d -mannopyranosyl 1-triphosphate or α- d -arabinopyranosyl 1-triphosphate were 8.0, 16.5, 9.6 or 14.1%, respectively. The phosphorylation mechanism of d -aldopyranoses with P 3m was also discussed.

The molecular modeling program STR3DI.EXE, and its molecular mechanics module, QVBMM, were used to simulate, and evaluate, the stereo-electronic effects in the mono-alkoxides of the 4,6- O -ethylideneglycopyranosides of allose, mannose, galactose and glucose. This study has confirmed the ability of these molecular modeling tools to predict the regiochemistry and reactivity of these sugar derivatives, and holds considerable implications for unraveling the chemistry of the rare monosaccharides.

A new branched-chain aldose, 2- C -(hydroxymethyl)- d -allose ( 3 ), was obtained by a base-catalysed addition of 2,3:5,6-di- O -isopropylidene-β- d -allofuranose to formaldehyde followed by acid hydrolysis of the aldol product. On treatment with a catalytic amount of molybdic acid at 90 °C, 3 afforded its equilibrium mixture with sedoheptulose tautomeric and anhydro forms in the ratio 12:1. Sedoheptulose in its 2,7-anhydro form, 2,7-anhydro-β- d - altro -heptulopyranose, was obtained from this mixture by treatment with 0.5 M H 2 SO 4 and crystallisation (overall 63% yield).

Immobilised glucose isomerase (EC 5.3.1.5) accepted various (2 R ,3 R ,4 R )-configured hexoses such as 5-deoxy- d - ribo -hexose, 5-azido-5-deoxy- d -allose, as well as the corresponding epimer at C-5, 5-azido-5-deoxy- l -talose, as substrates. From the resulting azidodeoxyketoses, 5-azido-5-deoxy- d -psico- and - l -tagatopyranose, the powerful d -galactosidase inhibitors 2,5-dideoxy-2,5-imino- d -galactitol and - d -altritol were obtained in one additional step.

Oxidation of the aldoses (Ald) d -glucose, d -allose, d -mannose, d -galactose, 6-deoxy- d -galactose ( d -fucose) and 2,6-dideoxy- d - ribo -hexose (digitoxose) by Cr VI yields the aldonic acid and Cr 3+ as final products when an excess of sugar over Cr VI is used. The redox reaction occurs through Cr VI →Cr III and Cr VI →Cr V →Cr III paths. The rate laws for the Cr VI and Cr V oxidation reactions are expressed by: −d[Cr VI ]/d t = k H [Ald][Cr VI ] and −d[Cr V ]/d t = k b K b [Ald][Cr V ]/(1+ K b [Ald]), where k H , k b and K b are the kinetic parameters independent of the [Ald] and [oxidant], and the relative aldoses reactivity with both Cr VI and Cr V is 2,6-dideoxy- d - ribo -hexose> d -galactose> d -allose> d -glucose≈6-deoxy- d -galactose, at 33 °C. Intermediate sugar alkoxide radicals could be trapped with 5,5-demethyl-1-pyrroline N -oxide (DMPO) and observed by electron paramagnetic resonance (EPR) as a multiline signal at g =2.003. Cr V is formed in a rapid step by the reaction of the sugar radical with Cr VI . The substrate is oxidised at a comparable rate by Cr VI and Cr V , especially at higher [Ald], and the reduction of Cr VI occurs concurrently with Cr V . The EPR spectra show that five- and six-coordinate oxochromate(V) intermediates are formed, with the aldose and/or the aldonic acid acting as bidentate ligands. Penta-coordinate Cr V species are present at any [H + ], whereas hexa-coordinate ones require stronger acid conditions.

ABC transport systems for import or export of nutrients and other substances across the cell membrane are widely distributed in nature. In most bacterial systems, a periplasmic component is the primary determinant of specificity of the transport complex as a whole. We report here the crystal structure of the periplasmic binding protein for the allose system (ALBP) from Escherichia coli , solved at 1.8 A resolution using the molecular replacement method. As in the other members of the family (especially the ribose binding protein, RBP, with which it shares 35 % sequence homology), this structure consists of two similar domains joined by a three-stranded hinge region. The protein is believed to exist in a dynamic equilibrium of closed and open conformations in solution which is an important part of its function. In the closed ligand-bound form observed here, d -allose is buried at the domain interface. Only the β-anomer of allopyranose is seen in the crystal structure, although the α-anomer can potentially bind with a similar affinity. Details of the ligand-binding cleft reveal the features that determine substrate specificity. Extensive hydrogen bonding as well as hydrophobic interactions are found to be important. Altogether ten residues from both the domains form 14 hydrogen bonds with the sugar. In addition, three aromatic rings, one from each domain with faces parallel to the plane of the sugar ring and a third perpendicular, make up a hydrophobic stacking surface for the ring hydrogen atoms. Our results indicate that the aromatic rings forming the sugar binding cleft can sterically block the binding of any hexose epimer except d -allose, 6-deoxy-allose or 3-deoxy-glucose; the latter two are expected to bind with reduced affinity, due to the loss of some hydrogen bonds. The pyranose form of the pentose, d -ribose, can also fit into the ALBP binding cleft, although with lower binding affinity. Thus, ALBP can function as a low affinity transporter for d -ribose. The significance of these results is discussed in the context of the function of allose and ribose transport systems.

New 3′,6′-dideoxy-3′,6′-epithio and 2′,6′-dideoxy-2′,6′-epithionucleosides were prepared from 3′,6′-dideoxy-3′,6′-epithioglucofuranose derivatives, which were obtained from 3-trifluoromethanesulfonyl diacetone allose.

d -(1,3,6- 13 C 3 )Allose ( 1 ), ( 13 C)methyl α - d -(1,2- 13 C 2 )glucopyranoside ( 2 ) and ( 13 C)methyl β - d -(1,2- 13 C 2 )glucopyranoside ( 3 ) were synthesized and used to establish the signs of their constituent 2 J CCC or 2 J COC values ( 2 J C1,C3 in the α -pyranose of 1 ( 15 ), and 2 J C1,CH 3 in 2 and 3 ). Compounds 2 , 3 and 15 contain three mutually coupled labeled carbons, thus creating a three-spin system from which crosspeak displacements in 13 C– 13 C COSY-45 spectra were used to determine coupling signs. In all compounds, at least one 3 J CC value was present as an internal reference: 3 J C2,CH 3 in 2 and 3 , and 3 J C1,C6 and 3 J C3,C6 in 15 . 2 J C1,CH 3 in 2 and 3 , and 2 J C1,C3 in 15 , were found to be negative, thus providing experimental confirmation of the sign predictions made via the projection resultant rule described recently.

Cyclophosphamides derived from alkyl 2-amino-4,6- O -benzylidene-2-deoxy- β - d -allopyranosides have been synthesized with good yield by treatment of the corresponding 2-amino-2-deoxy- d -allose derivatives with bis(2-chloroethyl)phosphoramide dichloride. The ring-forming reaction took place with very high diastereoselectivity. Subsequent hydrogenolysis gave excellent yields of cyclophosphamides derived from alkyl 2-amino-2-deoxy- β - d -allopyranosides, with hydrophilicity greater than that of the precursors. The starting material was easily available from 2-acetamido-2-deoxy- d -glucose.

The transesterification of D-allose (the C-3 epimer of D-glucose) with vinyl octanoate using Candida antarctica lipase in tetrahydrofuran proceeded with high regioselectivity to produce 6-O-octanoyl-D-allose with nearly complete conversion. The growth-inhibiting activity of 6-O-octanoyl-D-allose on lettuce seedlings was about 6-fold greater than that of D-allose.

This study investigated the formation of oxo groups in pure solutions of barley mixed-linkage (1 → 3),(1 → 4)-β- d -glucans (MLGs) incubated in the presence of hydrogen peroxide or Fenton reaction-generated hydroxyl radicals ( OH), and it gives a fingerprint of products obtained after enzymic and acidic hydrolysis of OH-attacked MLG. Hydroxyl radical, but not hydrogen peroxide, introduced a range of NaB3H4-reducible functions into MLG chains. Driselase or lichenase digestion of NaB3H4-reduced MLGs released a complex mixture of 3H-labelled products due to the presence of unusual and incompletely digestible residues in OH-attacked polysaccharide chains. Complete acid hydrolysis of OH-treated MLGs yielded a mixture of 3H-aldoses (mainly glucose, mannose, galactose and allose) deriving from random OH attack at positions 2, 3 or 4 to form glycosulose residues which were NaB3H4-reducible to epimeric mixtures of 3H-aldose residues. Furthermore, the production of [3H]glucitol demonstrated the radical-mediated cleavage of mid-chain glucose residues to create new reducing termini. Oxidative scission of MLGs by hydroxyl radical caused a decrease in molecular weight of about 96%, which was partially inhibited by the addition of DMSO, an OH scavenger. The results can be a starting point for developing an assay to detect changes due to OH attack of MLGs in vivo, or during food processing and storage, based on the chemical or enzymic release of unusual sugar residues such as allose as diagnostic products after reduction/labelling treatment and partial purification (or selective digestion by lichenase) of polymeric material.

Escherichia coli K-12 can utilize D-allose, an all-cis hexose, as a sole carbon source. The operon responsible for D-allose metabolism was localized at 92.8 min of the E. coli linkage map. It consists of six genes, alsRBACEK, which are inducible by D-allose and are under the control of the repressor gene alsR. This operon is also subject to catabolite repression. Three genes, alsB, alsA, and alsC, appear to be necessary for transport of D-allose. D-Allose-binding protein, encoded by alsB, is a periplasmic protein that has an affinity for D-allose, with a Kd of 0.33 microM. As was found for other binding-protein-mediated ABC transporters, the allose transport system includes an ATP-binding component (AlsA) and a transmembrane protein (AlsC). It was found that AlsE (a putative D-allulose-6-phosphate 3-epimerase), but not AlsK (a putative D-allose kinase), is necessary for allose metabolism. During this study, we observed that the D-allose transporter is partially responsible for the low-affinity transport of D-ribose and that strain W3110, an E. coli prototroph, has a defect in the transport of D-allose mediated by the allose permease.

Pseudomonas fluorescens lipase (PFL)-catalyzed asymmetric hydrolysis of meso -2,5-bis(acetoxymethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran 3 afforded the optically active monoacetate (−)- 7 of high enantiomeric excess (92% ee) in 94% yield. Transesterification of meso -bis(hydroxymethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran 6 using PFL in vinyl acetate gave the monoacetate (+)- 7 of 69% ee in low yield (15%). The absolute configuration of (−)- 7 was determined to be 2 S ,3 S ,4 R ,5 R , by chemical correlation with d -allose 10 .

The synthesis of a novel compound, 3-deoxy-3-fluoro-β-d-allopyranoside, is described. It involves blocking the 4- and 6-positions of allose to cause fluorination only at the 3-position. This six-step synthesis gave pure crystalline compound in a 5% overall yield. The crystal structure, determined by X-ray diffraction, confirmed the chemical formula and configuration of the product. It showed that the C-F bond isaxial, while the C-(OH) bonds areequatorial. The overall conformation of this fluoroallose is similar to that of allose (Acta Cryst.1984,C40, 1863) (with OH instead of F), but the packing in the two crystals is different in the region of C3, the site of chemical variation.

The acylation of the rare sugar, D-allose (the C-3 epimer of D-glucose), with fatty acid vinyl esters was successfully carried out using Candida antarctica lipase in acetonitrile at 45 degrees C to give D-allose 6-alkanoates with high regioselectivity in good yields.

A practical access to glucose-based and allose-based spirooxazolidinones is reported. The synthetic sequence consisting of TEMPO-catalyzed oxidation of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose, Henry reaction, and reduction provides amino alcohol with allo-configuration on a multigram scale. Alternatively, water elimination from Henry products followed by a rehydration gives an access to diastereomerically pure glucose-based nitro alcohol which upon reduction provides complementary amino alcohol with gluco-configuration. The latter amino alcohols are transformed into spirooxazolidinones (3-spiropseudonucleosides) via their N-Cbz or N-phenylcarbamate derivatives. The title compounds easily undergo N-derivatization and give highly crystalline materials. Two of the newly obtained (5+5) 3-spiropseudonucleosides are characterized by X-ray crystallography.

A series of eight potential peptidomimetics has been synthesised based on the use of gluco- and allo- carbohydrate derivatives as scaffolds to support appropriate side-chains which mimic the D- and L- aminoacid residues of the cyclic peptide endothelin antagonist BQ123 .

A new efficient synthesis of 3-amino-3-deoxy- d -altrose (13), 3-amino-3-deoxy- l -allose (17), and 4-amino-4-deoxy- d -talose (21) from 2,3-O- isopropylidene- d -glyceraldehyde (6) using N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsiloxy)pyrrole (TBSOP) as homologative nucleophile is described. The procedure highlights the merits of densely functionalized homochiral heptonolactam 9 as a key divergent intermediate.

In an unconventional but interesting synthetic enterprise, the commercially available hydrocarbon cyclooctatetraene (COT) has been elaborated to the rare hexose sugar (DL)-β-allose and its 2C-branched analogue. The synthetic sequence delineated here is notable for its high regio- and stereoselectivity and is flexible enough to enable access to polyoxygenated systems, hexose sugars, and their siblings from a cyclic polyene precursor.

The structure previously reported for coyolosa, a hypoglycemic substance isolated from natural sources, as a 6,6 ′ -ether linked pseudo-disaccharide derived from allose, is incorrect since 6- O -(6-deoxy- d -allos-6-yl)- d -allose 10 , synthesised by an unequivocal route, and its derived peracetate 11 , both have spectral properties, which differ from those reported for coyolosa and its peracetate. A versatile synthesis has been developed for this type of compound, containing two carbohydrate moieties joined through an ether linkage at their primary centres, which involves the displacement of a primary carbohydrate triflate with a carbohydrate alkoxide, and it allows the preparation of both symmetrical and unsymmetrical representatives of this class of compound.

The gene coding for ribose-5-phosphate isomerase (Rpi) from Thermotoga lettingae TMO was cloned and expressed in E. coli. The recombinant enzyme was purified by Ni-affinity chromatography. It converted d-psicose to d-allose maximally at 75 °C and pH 8.0 with a 32 % conversion yield. The k m, turnover number (k cat), and catalytic efficiency (k cat k m −1 ) for substrate d-psicose were 64 mM, 6.98 min−1 and 0.11 mM−1 min−1 respectively.

Unusual deoxy sugars are often attached to natural products such as antibiotics, antifungals, and chemotherapeutic agents. One such sugar is mycinose, which has been found on the antibiotics chalcomycin and tylosin. An intermediate in the biosynthesis of mycinose is dTDP-6-deoxy-D-allose. Four enzymes are required for the production of dTDP-6-deoxy-D-allose in Streptomyces bikiniensis, a soil-dwelling microbe first isolated from the Bikini and Rongelap atolls. Here we describe a combined structural and functional study of the enzyme ChmJ, which reportedly catalyzes the third step in the pathway leading to dTDP-6-deoxy-D-allose formation. Specifically, it has been proposed that ChmJ is a 3'-epimerase that converts dTDP-4-keto-6-deoxyglucose to dTDP-4-keto-6-deoxyallose. This activity, however, has never been verified in vitro. As reported here, we demonstrate using (1)H nuclear magnetic resonance that ChmJ, indeed, functions as a 3'-epimerase. In addition, we determined the structure of ChmJ complexed with dTDP-quinovose to 2.0 A resolution. The structure of ChmJ shows that it belongs to the well-characterized "cupin" superfamily. Two active site residues, His 60 and Tyr 130, were subsequently targeted for study via site-directed mutagenesis and kinetic analyses, and the three-dimensional architecture of the H60N/Y130F mutant protein was determined to 1.6 A resolution. Finally, the structure of the apoenzyme was determined to 2.2 A resolution. It has been previously suggested that the position of a conserved tyrosine, Tyr 130 in the case of ChmJ, determines whether an enzyme in this superfamily functions as a mono- or diepimerase. Our results indicate that the orientation of the tyrosine residue in ChmJ is a function of the ligand occupying the active site cleft.

A new type of rearrangement is described for 3-C-branched chain aldoses. The studied transformation is based on the Mo(VI)-catalyzed isomerization of carbohydrate carbon skeleton and allows preparation of C-3 isomers of 3-C-branched aldoses in a simple way without formation of side products. This rearrangement at C-3 carbon differs from the previously described epimerization at C-2 of aldoses catalyzed by Mo(VI) ions, known as Bilik reaction. The potential of this new transformation is illustrated on the preparation of new, 3- C -methyl- d -glucose and 3- C -vinyl- d -glucose from 3- C -methyl- d -allose and 3- C -vinyl- d -allose, respectively.

Molecular biosensors were developed and applied to measure individual sugars in biological mixtures such as bacterial culture broths. As the sensing units, four sugar-binding proteins (SBPs for allose, arabinose, ribose, and glucose) were selected from the Escherichia coli genome and connected to a cyan fluorescent protein and yellow fluorescent protein via dipeptide linkers (CFP-L-SBP-YFP). The putative sensors were randomized in the linker region (L) and then investigated with regard to the intensity of fluorescence resonance energy transfer on the binding of the respective sugars. As a result, four representatives were selected from each library and examined for their specificity using 16 available sugars. The apparent dissociation constants of the allose, arabinose, ribose, and glucose sensors were estimated to be 0.35, 0.36, 0.17, and 0.18 μM. Finally, the sugar sensors were applied to monitor the consumption rate of individual sugars in an E. coli culture broth. The individual sugar profiles exhibited a good correlation with those obtained using an HPLC method, confirming that the biosensors offer a rapid and easy-to-use method for monitoring individual sugars in mixed compositions.

The molecular mechanics algorithm MM3 was used to compute energy surfaces for aldopyranosyl rings having a full range of shapes. Energies were plotted against the ΦΘ puckering coordinates of Cremer and Pople. The 4 C 1 conformations of the model pyranosyl rings are dominant for both anomers of d -allose, d -galactose, d -glucose, d -mannose, and d -talose, as are the 4 C 1 conformations of β- d -altropyranose, β- d -gulopyranose, and β- d -idopyranose. α- d -Altropyranose is predicted to exist as an equilibrium of 1 C 4 and 4 C 1 , α- d -idopyranose as an equilibrium among O S 2 , 1 C 4 , and 4 C 1 , and α- d -gulopyranose is predominately 4 C 1 but has some contribution from 1 C 4 (18%) and O S 2 (9%). The calculated and measured hydrogen-hydrogen coupling constants agree well, although the energies for the β anomers in water are systematically low by an average of 0.4 kcal/mol. Because the errors in the predicted anomeric ratios are small and are similar for the eight hexoses, and because the only concession to the solvent was a dielectric constant of 3.0, specific solvent effects are apparently small.

Diels-Alder cycloaddition of sorbic aldehyde derivative 9 and of sorbic acid 10 with the chiral chloro-nitroso dienophile 7 led with excellent regio- and diastereoselectivity to the chiral cycloadducts 11a and 12 , respectively. Catalytic osmylation of their Bzl-derivatives 11b and 13b , followed by reductive cleavage of the NO bonds, gave ultimately the chiral aminoallose derivatives D-5 and D-6 which are potential glycosidase inhibitors.

The optically pure Diels-Alder adduct of furan to 1-cyanovinyl (1R)-camphanate was converted to methyl(methyl 5-bromo-5-deoxy-2,3-O-isopropylidene-β-l-allo-hexo-furanosid)uronate. Ester reduction, followed by HBr elimination afforded (+)-methyl 5,6-anhydro-2,3-O-isopropylidene-d-β-talo-hexofuranoside. Applying the method of Adley and Owen, (+)-methyl 5,6-dideoxy-5,6-epithio-2,3-O-isopropylidene-l-β-allo-hexofuranoside was obtained and acetolysed to give, after deprotection, (-)-5-deoxy-5-thio-l-allose.