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Spacer-Mediated Synthesis of Contra-Thermodynamic Spiroacetals: Stereoselective Synthesis of C₂-Symmetric Difructose Dianhydrides

Supporting Info

Enrique M. Rubio,^† M. Isabel García-Moreno,^‡ Patricia Balbuena,^† Fernando J. Lahoz,^§ Eleuterio Álvarez,^† Carmen Ortiz Mellet,*^‡ and José M. García Fernández*^†;

Instituto de Investigaciones Qumicas, CSIC, Amrico Vespucio 49, Isla de la Cartuja, E-41092 Sevilla, Spain, Departamento de Qumica Orgnica, Facultad de Qumica, Universidad de Sevilla, Aptdo. 553, E-41071 Sevilla, Spain, and Departamento de Qumica Inorgnica - I.C.M.A. Facultad de Ciencias, Universidad de Zaragoza - CSIC, 50009 Zaragoza, Spain

J. Org. Chem., 2006, 71 (6), pp 2257–2266

DOI: 10.1021/jo052184b

Publication Date (Web): February 18, 2006

†

Instituto de Investigaciones Químicas, CSIC.

‡

Universidad de Sevilla.

Universidad de Zaragoza - CSIC.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, jogarcia@iiq.csic.es, ; , mellet@us.es

Abstract

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.

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