Solvation effects on conformational equilibria. Studies related to the conformational properties of 2-methoxytetrahydropyran and related methyl glycopyranosides

Lemieux, R. U.; Pavia, A. A.; Martin, J. C.; Watanabe, K. A.

doi:10.1139/v69-731

Cited by 239 publications

(81 citation statements)

References 5 publications

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“…The starting alcohol (14) was prepared as previously reported (26). Glycosylation of 14 with acetobromoarabinose (7) under Helferich conditions produced 15, which on deacetylation provided the p-linked disaccharide (16) in 54% yield. Reaction of 16 with 2,2-dimethoxypropane in the presence of p-toluenesulfonic acid led to the alcohol (17) (91% yield), which in turn was reacted with 11 under halide-ion catalyzed conditions.…”

Section: Et3nmentioning

confidence: 99%

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

Spohr¹,

Paszkiewicz-Hnatiw²,

Morishima³

et al. 1992

Can. J. Chem.

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ULRIKE SPOHR, EUGENIA PASZKIEWICZ-HNATIW, NAOHIKO MORISHIMA, and RAYMOND U. LEMIEUX. Can. J . Chem. 70, 254 (1992).The relative potencies of a wide variety of deoxygenated derivatives of the methyl glycoside of a-L-Fuc-(1 -+ 2)-P-D-Gal-(1 -+ 4)-p-~-GlcNAc (the H-type 2 human blood group related trisaccharide) for the inhibition of the binding of an artificial H-type 2 antigen by the lectin I of Ulex europaeus confirmed the previous evidence that the key and productive interaction involves only the three hydroxyl groups of the a-L-fucose unit, the hydroxyl at the 3-position of the P-D-galactose residue, and the nonpolar groups in their immediate environment. Except for the acetamido group and the hydroxymethyl of the P -D -G~~ unit, which stay in the aqueous phase, on complex formation the remaining three hydroxyl groups appear to come to reside at or near the periphery of the combining site since their replacement by hydrogen causes relatively small changes (<* 1 kcal/mol) in the stability of the complex (AGO). Relatively much larger but compensating changes occur for the enthalpy and entropy terms, and these may arise primarily from the differences in the water structure about the periphery of the combining site and the oligosaccharide both prior to and after complexation. It is proposed that steric constraints lead to an ordered state of the water molecules hydrogen-bonded to the polar groups within the cleft formed by the key region of the amphiphilic combining site. Their release to form less ordered clusters of more strongly hydrogen-bonded water molecules in bulk solution would contribute importantly to the driving force for complexation. It is demonstrated that the surface used for the binding of H-type 2-OMe by a monoclonal anti-H antibody is virtually identical to that used by the Ulex lectin.Key words: molecular recognition, H-type 2 blood group determinant and deoxygenated derivatives, lectin I of Ulex europaeus, anti-H-type 2 monoclonal antibody, enthalpy-entropy compensation. Les efficacitCs relatives d'un grand nombre de dCrivCs dCsoxygCnCs du glycoside de mCthyle de l'a-L-Fuc-(I -+ 2)-P-D-Gal-(I -+ 4)-P-D-GlcNAc (trisaccharide reliC au groupe sanguin H de type 2 de l'homme) comme inhibiteurs de la fixation d'un antigkne artificiel du H de type 2 par la lectine I de 1'Ule.x europaeus ont confirmi les donnCes antCrieures suggCrant que cette interaction importante et productive n'implique que les trois groupes hydroxyles de I'unitC a-L-fucose, le groupe hydroxyle.en position 3 du rCsidu P-D-galactose et les groupes non-polaires qui se trouvent dans leur environnement immCdiat. A l'exception du groupe acetamido et de I'hydroxymCthyle de I'unitC P-D-Gal qui restent dans la phase aqueuse lors de la formation du complexe, il semble que les trois autres groupes hydroxyles se retrouvent a, ou pres de, la pCriphCrie du site qui effectue la combinaison; en effet, leur remplacement par de l'hydrogkne ne provoque que de faibles changements (<* 1 kcal/mol) dans la stabilitk du complexe (AGO). Des changements r...

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Section: Et3nmentioning

confidence: 99%

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

Spohr¹,

Paszkiewicz-Hnatiw²,

Morishima³

et al. 1992

Can. J. Chem.

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“…' The 2-alkoxytetrahydropyrans (3,11,12,13) were prepared, in the usual manner, by hydrogen chloride catalyzed addition of the alcohol to 2,3-dihydro-4H-pyran; 12: bp 69"C, 17 Torr (1 Torr = 133.3 Pa); 13: bp 126-127"C, 20 Torr. Deacetylation of 13 provided the 2-(2-hydroxyethoxy)tetrahydropyran (15) (bp 73-77"C, 3 Torr).…”

Section: General Proceduresmentioning

confidence: 99%

Influence of solvent on the magnitude of the anomeric effect

Praly¹,

Lemieux²

1987

Can. J. Chem.

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222

150

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This paper is dedicated to Dr. 0. E. (Ted) Edwards J.-P. PRALY and R. U. LEMIEUX. Can. J. Chem. 65, 213 (1987). A novel application of I3c nuclear magnetic resonance provided the effects of solvent polarity and hydrogen-bond formation on the conformational equilibria for a range of 2-substituted tetrahydropyrans and the results are interpreted in terms of how solvent affects the competition between the endo-and exo-anomeric effects in determining the magnitude of the anomeric effect. In accord with the generally accepted origin of the endo-and exo-anomeric effects (anti-periplanar n-a* interaction of the oxygen lone-pair orbital with the antibonding orbital of the adjacent C-0 bond), the exo-anomeric effect for the a anomer is expected to be weaker because charge delocalization from the glycosidic oxygen to anomeric center is in competition with delocalization from the ring-oxygen atom. The effects of solvent on the relative magnitudes of the endo-and exo-anomeric effects are then considered to arise from the formation of specific complexes with the solvent, and the exo-anomeric effect of a P-glycoside is more strongly influenced. It is contended that hydrogen bonding of solvent to the ring oxygen increases the exo-anomeric effects. For this reason water is particularly effective for the strengthening of the exo-anomeric effect and, thereby, the conformational rigidity of glycosides. Experimental evidence is presented that indicates that the anomeric hydroxyl groups of free sugars dissolved in water tend to prefer the equatorial orientation because these provide stronger hydrogen bonds as proton donors to water.

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“…Unless one of the oxygen is a hydroxyl group and can form a strong intramolecular hydrogen bond with the other gauehe oxygen one would expect a strong electrostatic repulsion between the two oxygen atoms. I would like now to present some NMR data which have suggested to us that this is indeed the case for certain methoxy derivatives of tetrahydropyran 12 and dioxan 13 in non-polar solvents. However, we are led to the tentative conclusion that water tends to substantially stabilize that conformation with the oxygens in gauehe relationship as compared to other solvents and that this may be for reasons of specific solvation effects.…”

mentioning

confidence: 89%

Newer developments in the conformational analysis of carbohydrates

Lemieux¹

1971

Pure and Applied Chemistry

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ABSTRACT·The lecture is mainly concerned with research from the author's laboratory on substitutional and solvation effects on conformational equilibria as estimated from NMR and optical rotation data. Reference is made to the use of empirical rules of rotation for estimating conformational preferences and to how x-ray crystallographic data on the torsional angles defined by vicinal atoms may become of importance to both the interpretation of rotation and NMR data. The anomeric and reverse anomeric effects on glycoside conformation are considered and reference is made to solvation effects on the interaction between oxygen atoms in gaueheandin syn-axial relationships. Effects of solvation on the orientation of the hydroxymethyl group of hexopyranoses and on intramolecular hydrogen bonding are presented.Remarkable advances were made in the past fifteen years in observing the conformational properties of carbohydrate structures. However, we are only beginning to probe the effects of the solvent in establishing the conformational preferences observed. The real value of conformational analysis will only be realized with a thorough understanding ofhow the carbohydrate solute interacts with the molecules in its environment and how this is related to conformational preferences as well as to how such interactions affect the energy requirements for changes in the environment of the carbohydrate. Answers to these questions are obviously of basic importance towards the eventual understanding ofthe enzyme-catalysed transformations of the carbohydrates, the antigenic properties of carbohydrate structures, the structure-activity relationships for carbohydrate antibiotics, etc. This lecture will be mainly concerned with our efforts to make contributions to this aspect of conformational analysis. Basic to our approach is the synthesis of model structures for which there should exist a substantial population of more than one conformation. Thus, solvation effects on the conformational equilibria for such compounds can be expected to be sufficiently large, to allow their observation, particularly through changes in nuclear magnetic resonance spectra and changes in optical rotation.As seen in Figure 1, this objective was realized by the preparation of methyl 3-deoxy-ß-L-erythro-pentopyranoside 1 . lt could be expected that in non-basie media, such as chloroform, an intramolecular hydrogen bond 527 P.A.C.-27/4---B

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Solvation effects on conformational equilibria. Studies related to the conformational properties of 2-methoxytetrahydropyran and related methyl glycopyranosides

Cited by 239 publications

References 5 publications

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

Molecular recognition XI. The synthesis of extensively deoxygenated derivatives of the H-type 2 human blood group determinant and their binding by an anti-H-type 2 monoclonal antibody and the lectin 1 of Ulexeuropaeus

Influence of solvent on the magnitude of the anomeric effect

Newer developments in the conformational analysis of carbohydrates

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