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Synthetic Approaches to Novel Archaeal Tetraether Glycolipid Analogues
Grégory Lecollinet1, Rachel Auzély-Velty, Mathieu Danel
1Ecole Nationale Supérieure de Chimie de Rennes, Laboratoire de Synthèses et Activations de Biomolécules, associé au CNRS, Avenue du Général Leclerc, 35700 Rennes, France, and The Department of Chemistry, Faculty of Science and the Environment, The University of Hull, Hull HU6 7RX, U.K.
Abstract:
Symmetrical and unsymmetrical archaeal tetraether glycolipid analogues have been prepared. The syntheses are based upon the elaboration of lipid cores from versatile chiral starting materials followed by simultaneous or sequential introduction of polar headgroups. Three pathways (A-C) were elaborated for the synthesis of stereochemically defined lipids 14-16 characterized by a straight bridging spacer and two dihydrocitronellyl chains attached to glycerol units at the sn-3 and sn-2 positions, respectively. Pathway C appeared to be particularly advantageous for the synthesis of tetraether 9, which possesses a cyclopentane unit as found in thermoacidophilic lipids. Diglycosylated lipids 4-6 were produced in 49-53% yields by reaction of diols 14-16 with beta-D-galactofuranosyl donor 31, whereas unsymmetrical lipids possessing either two different carbohydrate units 7 or a saccharidic moiety and a phosphate group 8 were efficiently prepared from monoprotected diol 35. These compounds represent the first examples of tetraether-type analogues containing a phosphate unit and/or glycosyl moieties.