Spacer-Mediated Synthesis of Contra-Thermodynamic Spiroacetals: Stereoselective Synthesis of C2-Symmetric Difructose Dianhydrides
| Autor: | M. Isabel García-Moreno, Fernando J. Lahoz, José Manuel García Fernández, Patricia Balbuena, Enrique M. Rubio, Eleuterio Alvarez, Carmen Ortiz Mellet |
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| Rok vydání: | 2006 |
| Předmět: |
Models
Molecular Anomer Stereochemistry Organic Chemistry Intermolecular force Molecular Conformation Diastereomer Stereoisomerism Fructose Crystallography X-Ray Molecular conformation Chemical synthesis Anhydrides chemistry.chemical_compound Acetals chemistry Spiro compounds Thermodynamics Moiety Spiro Compounds Stereoselectivity Xylylene Triflic acid |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 1520-6904 0022-3263 |
| DOI: | 10.1021/jo052184b |
| Popis: | 10 pages, 4 figures, 4 schemes. The xylylene moiety (ortho, meta, and para) was employed as a rigid tether in the spacer-mediated synthesis of difructose dianhydrides (DFAs), a unique class of bis-spiroacetal derivatives present in food products. The synthetic methodology exploits the suitability of triflic acid to promote spirocyclization in organic solvents under irreversible reaction conditions, using anomeric isopropylidene fructose derivatives as precursors. Advantage was taken of the strong dependence of the conformational properties of DFAs on the relative configuration of the spiroketal centers. Highly stereoselective syntheses of the contra-thermodynamic difructofuranose and difructopyranose diastereomers, namely the C2-symmetric derivatives having the β-configuration at both anomeric centers, have been accomplished by judicious choice of the xylylene positional isomer and of the linking position to the fructose building blocks. Interestingly, the rigid spacer concept has also been implemented to favor intermolecular processes leading to higher macrocyclic architectures that incorporate the bis-spiro fructodisaccharide subunit. We thank the Spanish Ministerio de Educación y Ciencia for financial support (Contract Nos. BQU2003-00937, CTQ2004-05854/BQU, and BQU2002-1729) and for a doctoral fellowship (to P.B.). E.M.R. thanks the CSIC and the Institut fu¨r Technologie der Kohlenhydrate e. V. for a fellowship. We also gratefully thank CCLRC Daresbury Laboratory for allocation of synchrotron beam time (AP41) and Dr. S. J. Teat for experimental assistance. |
| Databáze: | OpenAIRE |
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