Preface

Szarek, Walter A.; Horton, Derek

doi:10.1021/bk-1979-0087.pr001

Cited by 12 publications

(22 citation statements)

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“…Compound (II) was obtained by heating (I) in 60% acetic acid at 348 K for 40 min, followed by evaporation of the solvent under reduced pressure and crystallization of the product from a mixture of ethyl acetate and hexane. The analytical data for (I) and (II) were in accordance with those published previously (Szarek et al, 1997;Beaupere et al, 1989). Colourless single crystals of a quality adequate for diffraction analysis were obtained by slow crystallization of (I) from a 2:1 (v/v) mixture of diethyl ether and n-hexane under moderate cooling in a refrigerator.…”

Section: Methodsmentioning

confidence: 53%

“…The title isopropylidene derivatives of l-sorbofuranose, namely 2,3:4,6-di-O-isopropylidene--l-sorbofuranose, (I), and 2,3-O-isopropylidene--l-sorbofuranose, (II), are useful intermediates in organic synthesis. They have been used as starting materials for the stepwise synthesis of 1-deoxynojirimycin (Beaupere et al, 1989), the 6,6-difluoro analog (Szarek et al, 1997) and N-butyl-1-deoxynojirimycin (N-Bu DNJ, Zavesca 1 ) (Boucheron et al, 2005;Godin et al, 2002), known as a very efficient glycosidase inhibitor used, inter alia, as a therapeutic agent in the treatment of lysosomal disease. In the context of studies on the synthesis of imino-sugar derivatives related to nojirimycin and mannojirimycin, we have prepared (I) from l-sorbose using acetone as an isopropylidenation agent and concentrated sulfuric acid as a catalyst.…”

Section: Commentmentioning

confidence: 99%

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2,3:4,6-Di-O-isopropylidene-α-L-sorbofuranose and 2,3-O-isopropylidene-α-L-sorbofuranose

2009

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In the title compounds, C(12)H(20)O(6), (I), and C(9)H(16)O(6), (II), the five-membered furanose ring adopts a (4)T(3) conformation and the five-membered 1,3-dioxolane ring adopts an E(3) conformation. The six-membered 1,3-dioxane ring in (I) adopts an almost ideal (O)C(3) conformation. The hydrogen-bonding patterns for these compounds differ substantially: (I) features just one intramolecular O-H...O hydrogen bond [O...O = 2.933 (3) A], whereas (II) exhibits, apart from the corresponding intramolecular O-H...O hydrogen bond [O...O = 2.7638 (13) A], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) A]. This study illustrates both the similarity between the conformations of furanose, 1,3-dioxolane and 1,3-dioxane rings in analogous isopropylidene-substituted carbohydrate structures and the only negligible influence of the presence of a 1,3-dioxane ring on the conformations of furanose and 1,3-dioxolane rings. In addition, in comparison with reported analogs, replacement of the -CH(2)OH group at the C1-furanose position by another group can considerably affect the conformation of the 1,3-dioxolane ring.

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Section: Methodsmentioning

confidence: 53%

Section: Commentmentioning

confidence: 99%

2,3:4,6-Di-O-isopropylidene-α-L-sorbofuranose and 2,3-O-isopropylidene-α-L-sorbofuranose

2009

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“…The anomeric effect itself was first identified in carbohydrate chemistry by Lemieux in 1964 and is now recognized as having importance for many molecules with the X–C–Y linkage, where X and Y may be O, S, or Se. − The initial observation for sugars, contrary to expectations, was that the axial methoxyl at the anomeric carbon was more stable than its equatorial form. The anomeric effect in a molecule such as 1,3-dioxole is believed to involve donation of electron density from a lone pair on one oxygen atom into the adjacent carbon–oxygen bond.…”

Section: Introductionmentioning

confidence: 99%

“…The anomeric effect in a molecule such as 1,3-dioxole is believed to involve donation of electron density from a lone pair on one oxygen atom into the adjacent carbon–oxygen bond. The interaction results from n to σ* overlap ,− and is strongest when the −C–O–C–O torsional angle is at 90°. Thus, a planar conformation for the 1,3-dioxole ring would not have any anomeric interaction, but the experimentally determined puckering angle of 24° does allow substantial interaction.…”

Section: Introductionmentioning

confidence: 99%

Anomeric Effect in Five-Membered Ring Molecules: Comparison of Theoretical Computations and Experimental Spectroscopic Results

Ocola

Laane

2020

J. Phys. Chem. A

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analysis of the ring-puckering potential energy function (PEF) of a "pseudo-four-membered ring" molecule can provide insight into understanding the magnitude of the anomeric effect. In the present study, high-level CCSD/cc-pVTZ and somewhat lower-level MP2/ cc-pVTZ ab initio computations have been utilized to calculate the PEFs for 1,3-dioxole and 1,3-benzodioxole and 10 related molecules containing sulfur and selenium atoms and possessing the anomeric effect. The potential energy parameters derived for the PEFs directly provide a comparison of the relative magnitudes of the anomeric effect for molecules possessing OCO, OCS, OCSe, SCS, SCSe, and SeCSe linkages. The torsional potential energies produced by the anomeric effect for these linkages were estimated to range from 5.97 to 1.91 kcal/mol. The ab initio calculations also yielded the structural parameters, barriers to planarity, and ring-puckering angles for each of the 12 molecules studied. Based on the refined structural parameters for 1,3-dioxole and 1,3-benzodioxole, improved PEFs for these molecules were also calculated. The calculations also support the conclusion that the relatively low barrier to planarity of 1,3-benzodioxole results from competitive interactions between its benzene ring and the oxygen atom p orbitals.

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“…These orbital interactions govern, for instance, the conformational preference of a-glucosides over ß-glucosides and are collectively known as the anomeric effect, the generalized anomeric effect, or negative hyperconjugation. [15][16][17][18][19][20][21][22] In an a-glucoside, the electron density is donated from the ring oxygen lone pair to the s * orbital between the carbon atom and the polar oxygen atom. This favorable interaction is maximized when the recipient s * orbital is in the axial position, thus a-glucosides are preferred energetically over ß-glucosides.…”

Section: Introductionmentioning

confidence: 99%

What governs nitrogen configuration in substituted aminophosphines?

Wodrich

Vargas

Morgantini

et al. 2008

J of Physical Organic Chem

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The trigonal planar geometry of the nitrogen atom in commonly used phosphoramidite ligands is not in line with the traditional valence shell electron pair repulsion (VSEPR) model. In this work, the effects governing nitrogen configuration in several substituted aminophosphines, A 2 PNB 2 (A or B ¼ H, F, Cl, Br, Me, OMe, BINOP), are examined using modern computational analytic tools. The electron delocalization descriptions provided by both electron localization function (ELF) and block localized wavefunction analysis support the proposed relationships between conformation and negative hyperconjugative interactions. In the parent H 2 PNH 2 , the pyramidal nitrogen configuration results from nitrogen lone pair electron donation into the s * P-H orbital. While enhanced effects are seen for F 2 PNMe 2 , placing highly electronegative fluorine substituents on nitrogen (i.e., Me 2 PNF 2 ) eliminates delocalization of the nitrogen lone pair. Understanding and quantifying these effects can lead to greater flexibility in designing new catalysts.

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Preface

Cited by 12 publications

References 0 publications

2,3:4,6-Di-O-isopropylidene-α-L-sorbofuranose and 2,3-O-isopropylidene-α-L-sorbofuranose

2,3:4,6-Di-O-isopropylidene-α-L-sorbofuranose and 2,3-O-isopropylidene-α-L-sorbofuranose

Anomeric Effect in Five-Membered Ring Molecules: Comparison of Theoretical Computations and Experimental Spectroscopic Results

What governs nitrogen configuration in substituted aminophosphines?

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