Synthesis and Characterization of Four Diastereomers of Monorhamnolipids

Ricardo Palos Pacheco, Ryan J. Eismin, Clifford S. Coss, Hui Wang, Raina M. Maier, Robin Polt, Jeanne E. Pemberton

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Rhamnolipids are amphiphilic glycolipids biosynthesized by bacteria that, due to their low toxicity and biodegradability, are potential replacements for synthetic surfactants. The previously limited access to pure materials at the gram scale has hindered extensive characterization of rhamnolipid structure-performance behavior. Here, we present an efficient and versatile synthetic methodology from which four diastereomers of the most common monorhamnolipid, α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate, are prepared and subsequently characterized. Exploration of their behavior at the air-water interface is reported and analyzed in terms of the absolute configuration of the lipid tail carbinols at pH 4.0 and 8.0. All diastereomers exhibit a minimum surface tension of about 28 mN/m without a significant difference between the protonated (nonionic) or deprotonated (anionic) states. At pH 4.0 (nonionic), all diastereomers have a critical micelle concentration (CMC) in the micromolar range. At pH 8.0 (anionic), CMC values for the (R,R), (S,S), and (S,R) diastereomers are approximately an order of magnitude higher than in their nonionic states, whereas the (R,S) diastereomer exhibits a CMC about five times larger.

Original languageEnglish (US)
Pages (from-to)5125-5132
Number of pages8
JournalJournal of the American Chemical Society
Volume139
Issue number14
DOIs
StatePublished - Apr 12 2017

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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