Towards Functional Fluorous Surfactants. Synthesis and Spectroscopic Features of Systematically Modified Sugar-Substituted Fluorous 1,2,3-Triazoles

Abstract

ABSTRACT A library of 10 series of homologous compounds making up a total of 30 new, fluorous 1-substituted 1,2,3-triazol-4-ylmethyl(and ethyl) ether surfactant candidates, with highly systematic variations in substituent position and type, have been synthesised in consistently good yields by processes involving copper(I)-accelerated Huisgen-Meldal dipolar cycloaddition reactions. Each series contains a perfluorobutylethyl, perfluorohexylethyl or perfluorooctylethyl substituents at triazole position N(1) or attached through the triazole ether oxygen, and either a 1-β-D-glucosyl or 6-α-D-galactosyl substituent at the alternative triazole position. Half the library was prepared directly with the sugar components in a protected form (peracetylated glucose derivatives and 1,2:3,4-bisacetonide galactose derivatives) while the other series with unprotected sugars were obtained following a secondary deprotection step by trans-esterification using sodium methoxide or acid catalysed acetal solvation. All the triazoles are candidates for study as fluorous surfactants that are switchable between amphiphilic partner states, hydrophobic in the case of protected sugars and hydrophilic in unprotected sugars. As a prelude to surfactant studies, the NMR spectroscopic characteristics of the newly establish library of compounds were examined. Data were compared and contrasted within and between each series with reference to related literature analogues. Analysis of unprotected 6-galactosyl derivatives was complicated by the well known generation of inseparable, epimeric mixtures of hemiacetal pyranose and furanose products and the general paucity in the literature of NMR spectroscopic data assignments of signals from 1-β-hydroxygalactopyranose compounds. These matters have been addressed in this paper and the comparisons include analyses of unprotected 1'-α- and 1'-β-hydroxy-pyranose derivatives.