Conformational studies on aldonolactones by n.m.r. spectroscopy. Conformations of d-glucono-1,5-lactone and d-mannono-1,5-lactone in solution

Wałaszek, Zbigniew; Horton, Derek; Ekiel, Irena

doi:10.1016/s0008-6215(00)81073-3

Cited by 56 publications

(50 citation statements)

References 28 publications

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“…Comparison of the NMR spectroscopic data for δ--galactonolactone (6a) with those of δ--gluconolactone (4a) and δ--mannonolactone (5a) in [D 6 ]DMSO (Author: qui ϭ quintuplett; o ϭ octuplett). [a] Value as reported by Walaszek et al [23] and measured in the presence of CF 3 CO 2 H. [b] Not reported by the authors because of the presence of CF 3 CO 2 H.…”

Section: Synthesis and Isolation Of δ-Lactonesmentioning

confidence: 99%

δ‐Galactonolactone: Synthesis, Isolation, and Comparative Structure and Stability Analysis of an Elusive Sugar Derivative

Bierenstiel

Schlaf

2004

Eur J Org Chem

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δ‐D‐Gluconolactone, δ‐D‐mannonolactone, and — for the first time — the thermodynamically unstable δ‐D‐galactonolactone have been prepared and isolated from DMF solution by oxidizing the corresponding sugars with Shvo’s catalyst [(C4Ph4CO)(CO)2Ru]2 and a hydrogen acceptor. The preferred conformation of δ‐D‐galactonolactone in [D6]DMSO solution has been determined by 1H NMR spectroscopy experiments and DFT calculations to be 4H3 and is compared to those of the previously established conformations of δ‐D‐gluconolactone (4H3) and δ‐D‐mannonolactone (B2,5). The conformations of the lactones suggest an explanation for their relative rates of isomerization to their respective γ‐D‐lactones by an intramolecular mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Section: Synthesis and Isolation Of δ-Lactonesmentioning

confidence: 99%

δ‐Galactonolactone: Synthesis, Isolation, and Comparative Structure and Stability Analysis of an Elusive Sugar Derivative

Bierenstiel

Schlaf

2004

Eur J Org Chem

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“…Additional evidence for the relevance of the B 2,5 conformation comes from the observations that d-mannono-1,5-lactone and 5- amino-5-deoxy-d-mannono-1,5-lactam, both sp 2 hybridized at C1, also favor this unusual boat conformation. [14] The proposal of a 1 S 5 !B 2,5 ! O S 2 conformational change for a retaining b-mannanase predicted both that retaining amannosidases could utilize a "reverse" conformational agenda (…”

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confidence: 99%

“…Subsequently, the b-linked covalent intermediate for the family of GH38 retaining a-mannosidases has indeed been observed in 1 S 5 conformation [15] and likewise, a significant number of compounds with "pseudoequatorial" C2 substituents have been shown to be inhibitors of b-mannosidases. [12,14,16] One of the important, indeed controversial, aspects of glycosidase catalysis is whether sequence and structurally related enzymes working on different glycoside substrates adopt similar, or markedly different, conformational approaches to catalysis; does the enzyme, the substrate, or a subtle interplay of both dictate the catalytic itinerary and transition-state conformation? Comparison of the family GH26 b-mannanases and lichenses that are specific for manno-and gluco-configured substrates, respectively, in the light of wider work on other glycosidase families, suggests that the conformational agenda adopted is necessarily a subtle interplay of enzyme-structure-derived geometric constraints and the stereoelectronic and steric dictates of the substrate.…”

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Substrate Distortion by a Lichenase Highlights the Different Conformational Itineraries Harnessed by Related Glycoside Hydrolases

et al. 2006

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“…[12] Glycoside hydrolases thus appear to be harnessing the full conformational itinerary in a way that is both enzyme and substrate dependent (this was recently reviewed in the context of inhibition by Vasella and colleagues).…”

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confidence: 99%

Common Inhibition of Both β‐Glucosidases and β‐Mannosidases by Isofagomine Lactam Reflects Different Conformational Itineraries for Pyranoside Hydrolysis

et al. 2004

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The ninety sequence-based families of glycoside hydrolases (GHs) [1] and the correspondingly large diversity of protein topologies [2] are a rich framework for studying variations in the catalytic mechanism of enzymatic glycoside hydrolysis. Such hydrolysis features oxocarbenium-ion-like transition states in which the anomeric centre becomes sp 2 hybridised and partial positive charge accumulates, primarily across the endocyclic O5ÀC1 bond. For pyranosides, such a species demands planarity of C5, O5, C1 and C2 at or near the transition state; a situation accommodated only by the 4 H 3 and 3 H 4 (half-chair) conformations (or their closely related envelope forms) and 2,5 B and B 2,5 boats. Initial assumptions that all glycosidases harness 4 H 3 conformations are incorrect; indeed, the utilisation of different transition states for the hydrolysis of glycosides is an emerging theme in glycobiology (Scheme 1) [3] and one that suggests a route for specific enzyme inhibition. Isofagomine lactam (1) displays an "in-plane" carbonyl at C2 and is, not surprisingly, a reasonable b-glucosidase inhibitor, with family GH1 b-glucosidases from Thermotoga maritima (TmGH1) and sweet almond inhibited with K i values of 130 nm (this work, Figure 1) and 29 mm, [4] respectively. Compound 1 has previously been shown to be an equally potent b-mannosidase inhibitor, [4] with the snail b-mannosidase inhibited with a K i of 9 mm; this is superficially extremely counter-intuitive. Here, such K i values for mannosidases are rationalised through structural analysis of 1 in complex with both an exo b-mannanase/b-mannosidase and a b-glucosidase. This work strongly supports previous proposals that b-mannosidases utilise a novel conformational itinerary, featuring a B 2,5 transition state. The ground-state axial O2 of mannose is thus pseudo-equatorial at the transition state in a way that should be harnessed in future generations of mannosidase inhibitors.Recently we described the conformational agenda of a retaining GH26 b-mannanase.[6] Trapping of the 1 S 5 conformation for the "Michaelis" complex of unhydrolysed substrate, together with the O S 2 conformation for the covalent intermediate, suggested a novel conformational itinerary for these enzymes through a B 2,5 transition state consistent with earlier proposals, notably by Sinnott [11] and Horton. [12] Glycoside hydrolases thus appear to be harnessing the full conformational itinerary in a way that is both enzyme and substrate dependent (this was recently reviewed in the context of inhibition by Vasella and colleagues).[13] Conformational considerations suggest that retaining mannosidase transition-state mimics should thus feature the pseudo-equatorial O2 of the B 2,5 conformation of mannose.Isofagomine lactam 1, synthesised by both Stick [14] and Bols, [4] contains an in-plane carbonyl at C2. In elegant work, Bols reports a K i of 9 mm for the snail b-mannosidase;[4] this inspired us to study the three-dimensional structures of 1 bound to both TmGH1 and a Cellvibrio mixtus exo b-mannanase...

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Conformational studies on aldonolactones by n.m.r. spectroscopy. Conformations of d-glucono-1,5-lactone and d-mannono-1,5-lactone in solution

Cited by 56 publications

References 28 publications

δ‐Galactonolactone: Synthesis, Isolation, and Comparative Structure and Stability Analysis of an Elusive Sugar Derivative

δ‐Galactonolactone: Synthesis, Isolation, and Comparative Structure and Stability Analysis of an Elusive Sugar Derivative

Substrate Distortion by a Lichenase Highlights the Different Conformational Itineraries Harnessed by Related Glycoside Hydrolases

Common Inhibition of Both β‐Glucosidases and β‐Mannosidases by Isofagomine Lactam Reflects Different Conformational Itineraries for Pyranoside Hydrolysis

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