title: Design, synthesis and stimuli responsive gelation of novel stigmasterol-amino acid conjugates.
abstract: An efficient synthesis of three novel stigmasterol-amino acid (glycine, L-leucine and L-phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and L-leucinate form gels in n-alcohols (n=4-10) and in ethane-1,2-diol, and that of stigmasteryl L-phenylalaninate forms gels in aromatic solvents and in tetrachloromethane. These unique properties of the gelators were explored to prepare stimuli responsive, "acid-base" triggered reversible sol-gel transitions. The gelators and their gels were characterized by liquid and solid-state NMR as well as FT-IR. The morphology of their corresponding xerogels was investigated by SEM.
authors.affiliation: Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland. hana.svobodova@jyu.fi
authors.forename: Hana
authors.initials: H
authors.lastname: Svobodová
authors.lastname: Nonappa
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Wimmer
authors.forename: Erkki
authors.initials: E
authors.lastname: Kolehmainen
mesh_terms: D001688:Biological Products / Q000138:chemical synthesis*; D003692:Delayed-Action Preparations / Q000138:chemical synthesis*; D005782:Gels / Q000138:chemical synthesis*; D005998:Glycine / Q000737:chemistry; D006851:Hydrochloric Acid / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007930:Leucine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D044367:Phase Transition; D010649:Phenylalanine / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013265:Stigmasterol / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D001688:Biological Products; D003692:Delayed-Action Preparations; D005782:Gels; D012997:Solvents; D014867:Water; D010649:Phenylalanine; D013265:Stigmasterol; D007930:Leucine; D006851:Hydrochloric Acid; D005998:Glycine