Vesna Čaplar

11-Aminoundecanoic acid: a versatile unit for the generation of low molecular weight gelators for water and organic solvents

The use of 11-aminoundecanoic acid as a synthetic building-block allows the systematic preparation of (oligo)amide organogelators-including chiral ones-which display remarkable gelation properties in organic solvents and water.

Novel bis-phenanthridine derivatives with easily tunable linkers, study of their interactions with DNA and screening of antiproliferative activity

Series of novel peptide-bridged bis-phenanthridine derivatives as well as corresponding monomers were prepared by solid phase peptide synthesis, which allowed easy and fast tuning of compound properties. Interactions of new derivatives with double stranded DNA were strongly structure-dependent, among which the most interesting is bis-phenanthridine derivative forming intramolecular excimer, with specific fluorescence band sensitive to the pH as well as on the interactions with ds-DNA. Moreover, at variance to commonly high cytotoxic effects of phenanthridine derivatives, here studied monomeric as well as bis-phenanthridine derivatives exhibited negligible antiproliferative activity on a panel of human cell lines, which makes them promising lead compounds for development of new spectrophotometric markers.

Oxalyl retro-peptide gelators. Synthesis, gelation properties and stereochemical effects

Summary In this work we report on gelation properties, self-assembly motifs, chirality effects and morphological characteristics of gels formed by chiral retro-dipeptidic gelators in the form of terminal diacids (1a–5a) and their dimethyl ester (1b–5b) and dicarboxamide (1c–5c) derivatives. Terminal free acid retro-dipeptides (S,S)-bis(LeuLeu) 1a, (S,S)-bis(PhgPhg) 3a and (S,S)-bis(PhePhe) 5a showed moderate to excellent gelation of highly polar water/DMSO and water/DMF solvent mixtures. Retro-peptides incorporating different amino acids (S,S)-(LeuPhg) 2a and (S,S)-(PhgLeu) 4a showed no or very weak gelation. Different gelation effectiveness was found for racemic and single enantiomer gelators. The heterochiral (S,R)-1c diastereoisomer is capable of immobilizing up to 10 and 4 times larger volumes of dichloromethane/DMSO and toluene/DMSO solvent mixtures compared to homochiral (S,S)-1c. Based on the results of 1H NMR, FTIR, CD investigations, molecular modeling and XRPD studies of diasteroisomeric diesters (S,S)-1b/(S,R)-1b and diacids (S,S)-1b/(S,R)-1a, a basic packing model in their gel aggregates is proposed. The intermolecular hydrogen bonding between extended gelator molecules utilizing both, the oxalamide and peptidic units and layered organization were identified as the most likely motifs appearing in the gel aggregates. Molecular modeling studies of (S,S)- 1a/(S,R)-1a and (S,S)-1b/(S,R)- 1b diasteroisomeric pairs revealed a decisive stereochemical influence yielding distinctly different low energy conformations: those of (S,R)-diastereoisomers with lipophilic i-Bu groups and polar carboxylic acid or ester groups located on the opposite sides of the oxalamide plane resembling bola amphiphilic structures and those of (S,S)-diasteroisomers possessing the same groups located at both sides of the oxalamide plane. Such conformational characteristics were found to strongly influence both, gelator effectiveness and morphological characteristics of gel aggregates.

BIS-ADENINYL AND BIS-URACILYL HEXADIYNE DERIVATIVES OF NUCLEOBASES

Abstract Propaggyl derivatives of adenine, uracil and N(3)-substituted uracil have been prepared. Rigid 2,4-hexadiyne chains in dimeric compounds were obtained by Eglintonss oxidative dimerization with copper (II) acetate.

Hydrogen bonding topology influences gelating properties of malonamides

Preparation, structural characterisation and topology of hydrogen bonding networks of bis(phenylglycinol)malonamide, as well as its Cα mono- and dialkyl-substituted derivatives are described. Their hydrogen bonding motifs are described in view of their gelling properties. Topology of hydrogen bonding typical of malonamide gelators is compared with those of well-examined oxalamide gelators.