Macrocyclic Ionic Liquids with Amino Acid Residues: Synthesis and Influence of Thiacalix[4]arene Conformation on Thermal Stability

Abstract

Novel thiacalix[4]arene based ammonium ionic liquids (ILs) containing amino acid residues (glycine and L-phenylalanine) in cone, partial cone, and 1,3-alternate conformations were synthesized by alkylation of macrocyclic tertiary amines with N-bromoacetyl-amino acids ethyl ester followed by replacing bromide anions with bis(trifluoromethylsulfonyl)imide ions. The melting temperature of the obtained ILs was found in the range of 50–75 °C. The effect of macrocyclic core conformation on the synthesized ILs’ melting points was shown, i.e., the ILs in partial cone conformation have the lowest melting points. Thermal stability of the obtained macrocyclic ILs was determined via thermogravimetry and differential scanning calorimetry. The onset of decomposition of the synthesized compounds was established at 305–327 °C. The compounds with L-phenylalanine residues are less thermally stable by 3–19 °C than the same glycine-containing derivatives.

Towards Protection of Nucleic Acids from Herbicide Attack: Self-Assembly of Betaines Based on Pillar[5]arene with Glyphosate and DNA

“…A significant number of synthesized macrocyclic compounds (cyclodextrins, cucurbiturils, calixarenes, and their thia-analogues, pillararenes) are capable of binding guest molecules in water [45][46][47][48][49][50]. Furthermore, the introduction of small peptide fragments into the structure of macrocycles has shown the possibility of creating water-soluble receptors, which adopt a well-defined and precisely controlled secondary structure [51,52].…”

Recent Advances in the Synthesis and Applications of Ionic Liquids Derived from Natural Products

“…Aiming to study the influence of macrocycle conformation and amino acids on the thermal stability of macrocyclic ionic liquids, Padnya, Stoikov, and their co-workers reported the synthesis 64 of p - tert -butylthiacalixarenes bearing at the lower rim quaternary ammonium groups linked to glycine ( 161 ) or l -phenylalanine ( 162 ) in cone, partial cone, and 1,3-alternate blocked conformations (Scheme 29 ). First, glycine 153 and l -phenylalanine 148 were transformed into the corresponding bromoamido esters 154 and 155 by esterification followed by coupling with bromoacetyl bromide.…”

“…The individual stereoisomeric 157 was reacted with N , N -dimethyl-1,3-diaminopropane to afford the known 66 cone - 158 (90%), or the known 67 1,3 -alternate - 158 (95%), or the partial cone - 158 (yield and analytical data not provided). These compounds were then coupled 64 with glycine ( 154 ) or l -phenylalanine ( 155 ) derivatives in refluxing acetonitrile to give the ammonium bromide salts 159 and 160 , respectively. Finally, standard anion metathesis in the presence of lithium bistriflimide led to ILs 161 and 162 in almost quantitative yield.…”