142975-31-3Relevant academic research and scientific papers
Steroidal guanidinium receptors for the enantioselective recognition of N-acyl α-amino acids
Davis, Anthony P.,Lawless, Laurence J.
, p. 9 - 10 (1999)
Guanidinium cations 4 and 5 extract N-acetyl α-amino acids into CHCl3 from an aqueous medium with enantiomeric excesses of up to 80%.
Two-channel dansyl/tryptophan emitters with a cholic acid bridge as reporters for local hydrophobicity within supramolecular systems based on bile salts
Gomez-Mendoza,Marin, M. Luisa,Miranda, Miguel A.
, p. 8499 - 8504 (2014)
The aim of the present work is to develop two-channel emitters to probe local hydrophobicity by means of fluorescence quenching within different biomimetic supramolecular environments. To achieve this goal, the dansyl (Dns) and tryptophan (Trp) fluorophores have been covalently attached to cholic acid (CA) in order to ensure simultaneous incorporation of the two emitting units into the same compartment. In principle, the two fluorophores of the synthesized Dns-CA-Trp probes could either exhibit an orthogonal behavior or display excited state interactions. The fluorescence spectra of 3β-Dns-CA-Trp showed a residual Trp emission band at ca. 350 nm and an enhanced Dns maximum in the 500-550 nm region. This reveals a partial intramolecular energy transfer, which is consistent with the Dns and Trp singlet energies. Thus, the two photoactive units are not orthogonal; nevertheless, 3β-Dns-CA-Trp seems appropriate as a two-channel reporter for the supramolecular systems of interest. Fluorescence quenching of 3β-Dns-CA-Trp by iodide (which remains essentially in bulk water) was examined within sodium cholate, sodium taurocholate, sodium deoxycholate and mixed micelles. Interestingly, a decrease in the emission intensity of the two bands was observed with increasing iodide concentrations. The most remarkable effect was observed for mixed micelles, where the quenching rate constants were one order of magnitude lower than in solution. As anticipated, the quenching efficiency by iodide decreased with increasing hydrophobicity of the microenvironment, a trend that can be correlated with the relative accessibility of the probe to the ionic quencher. This journal is
Influence of Conformational Change and Interligand Hydrogen Bonding in a Chiral Metal-Organic Cage
Sen, Shovan Kumar,Natarajan, Ramalingam
, p. 7180 - 7188 (2019)
We report about the coordination-driven self-assembly of a chiral bis-pyridyl ligand (1), synthesized from steroidal cholic acid, with Pd(II) ions to form a chiral metal-organic Pd2(1)4 cage. The self-assembly of the cage was facilitated by favorable conformational change in the alkyl chain of the cholic acid. Interligand hydrogen bonding played a crucial role in directing the formation of a C4 symmetric cage among different possible isomers, as suggested by DFT studies, and control experiments with different ligands.
Oligomeric cholates: Amphiphilic foldamers with nanometer-sized hydrophilic cavities
Zhao, Yan,Zhong, Zhenqi
, p. 17894 - 17901 (2005)
The hydroxyl at the C-3 of cholic acid was converted to an amino group, and the resulting amino-functionalized cholic acid was used as a monomer to prepare amide-linked oligomeric cholates. These cholate oligomers fold into helical structures with nanometer-sized hydrophilic internal cavities in solvent mixtures consisting of mostly nonpolar solvents such as carbon tetrachloride or ethyl acetate/hexane and 2-5% of a polar solvent such as methanol or DMSO. The conformations of the foldamers were studied by UV, fluorescence, fluorescence quenching, and fluorescence resonance energy transfer. The nature of the polar/nonpolar solvents and their miscibility strongly influenced the folding reaction. Folding was cooperative, as evidenced by the sigmoidal curves in solvent denaturation experiments. The folded conformers became more stable with an increase in the chain length. The folding/unfolding equilibrium was highly sensitive toward the amount of polar solvent. One percent variation in the solvent composition could change the folding free energies by 0.5-1.4 kcal/mol.
Improving reactivity and selectivity of aqueous-based Heck reactions by the local hydrophobicity of phosphine ligands
Roberts, Gina M.,Zhang, Shiyong,Zhao, Yan,Woo, L. Keith
, p. 8263 - 8270 (2015/10/05)
Modification of a triarylphosphine with a cholate moiety affords a new ligand, 1, which is effective in palladium-catalyzed Heck cross-couplings between acrylates and aryl iodides under mild, aqueous reaction conditions. High yields, up to 99%, were achieved in water at 40 °C. In competition studies, a more hydrophobic substrate (n-Bu acrylate) was preferred over the least hydrophobic substrate (methyl acrylate), supportive of a localized hydrophobic microenvironment near the catalytic center. The enhanced reactivity and selectivity for hydrophobic substrates disappeared when the local hydrophobicity was eliminated using a standard water-soluble phosphine or in organic solvents.
One-pot Mitsunobu-Staudinger preparation of 3-aminocholan-24-oic acid esters from 3-hydroxychlan-24-oic acid esters
Anelli, Pier Lucio,Lattuada, Luciano,Uggeri, Fulvio
, p. 109 - 117 (2007/10/03)
3-Hydroxycholan-24-oic acid esters are easily converted into the corresponding 3-amino derivatives via Mitsunobu reaction with diphenylphosphoryl azide (DPPA) and Staudinger reduction with PPh3/H2O of the intermediate azido compound
