Search results for "DISCOVERY"
showing 10 items of 4119 documents
Cyclodextrin-[60]fullerene conjugates: synthesis, characterization, and electrochemical behavior
2006
Three different functionalized β-cyclodextrins (β-CDs) bearing the C60 moiety linked covalently have been prepared in good yields by reaction between the parent β-CD and [60]fullerene via 1,3-dipolar cycloaddition. These compounds have been fully spectroscopically characterized and their electrochemical behavior has been investigated. Surprisingly, the electrochemical properties of the C60 cage remain unaltered even after chemical functionalization, making these systems very appealing as supramolecular hosts for electron-transfer processes.
Synthesis of a Fullerene Derivative of Benzo[18]crown-6 byDiels-Alder Reaction: Complexation Ability, Amphiphilic Properties, and X-Ray Crystal Struc…
1993
A fullerene derivative 1 of benzo[18]crown-6 was obtained by Diels-Alder addition of fullerene[60](C60) to the ortho-quinodimethane prepared in situ from 4,5-bis(bromomethyl)benzo[18]crown-6 (3) with Bu4NI in toluene. Extraction experiments show that the complexation of K+ ions strongly increases the solubility of 1 in protic solvents like MeOH. Using Langmuir-Blodgett techniques, monolayers of the highly amphiphilic fullerene-derived crown ether 1 and its K+ ion complex were prepared. An X-ray crystal structure was obtained from a benzene clathrate of comparison compound 2, synthesized by Diels-Alder reaction of C60 with the ortho-quinodimethane derived from 1,2-bis(bromomethyl)-4,5-dimeth…
A novel germacranolide-aminoacid adduct dimer from centaurea aspera
1991
Abstract The novel germacronolide-valine adduct dimer 1 has been isolated from aerial parts of Centaurea aspera var. aspera . Its structure has been determined by spectroscopic methods.
Cyclodextrin-assisted Glycan Chain Extension on a Protected Glycosyl Amino Acid
2000
By the use of cyclodextrins, we have enhanced the solubility of the protected amino acid glycan Fmoc-Thr(GalNAcα1)-OtBu (1b) up to 100-fold. This improvement enabled us to carry out an enzymatic glycosylation employing a β-galactosidase in combination with an α2,3-sialyltransferase without the aid of organic cosolvents. After optimization of the one-pot reaction, the sialylated core 1 structure Fmoc-Thr[Neu5Ac(α2-3)Gal(β1-3)GalNAcα1]-OtBu (3b) could be obtained with 50% yield.
Carbohydrates as chiral templates: Diastereoselective Ugi synthesis of (S)-amino acids using O-acylated D-arabinopyranosylamine as the auxiliary
1989
Abstract Enantiomerically pure (S)-amino acids are synthesized via a highly diastereoselective Ugi reaction using 2,3,4-tri-O-pivaloyl-α-D-arabinopyranosylamine as the chiral template.
Enzymatic glycosylation of o-glycopeptides
1992
Abstract O-Glycosylation of serine derivatives carried out with N-urethane protected glucosamine yields O-glycopeptides which are regio- and stereoselectively galactosylated with the aid of β-1,4-galactosyltransferase (EC 2.4.1.22).
Tailor‐Made Amino Acids and Fluorinated Motifs as Prominent Traits in Modern Pharmaceuticals
2020
Structural analysis of modern pharmaceutical practices allows for the identification of two rapidly growing trends: the introduction of tailor-made amino acids and the exploitation of fluorinated motifs. Curiously, the former represents one of the most ubiquitous classes of naturally occurring compounds, whereas the latter is the most xenobiotic and comprised virtually entirely of man-made derivatives. Herein, 39 selected compounds, featuring both of these traits in the same molecule, are profiled. The total synthesis, source of the corresponding amino acids and fluorinated residues, and medicinal chemistry aspects and biological properties of the molecules are discussed.
Calix[4]arenes with resorcinol units incorporated in 2,6-position
1990
Abstract Calix[4]arenes containing one or two resorcinol units incorporated via their 2,6-positions were prepared by fragment condensation. Due to the cyclic array of intramolecular hydrogen bonds these molecules assume the cone-conformation.
Fluorescent 3-amino-1,8-naphthalimide Tröger’s bases (3-amino-TBNaps) incorporating protected α-amino acids
2021
Abstract The synthesis of 3-amino-1,8-naphthalimide Troger’s base’s (TBNaps) 2–4, possessing several amino acids at the imide terminus, from the corresponding 3-amino-1,8-naphthalimide (Naps) units is described. The solid-state X-ray crystal structure of the related 3-amino-TBNaps piperidino-ethyl derivative 1, and its supramolecular packing is also outlined. In these molecules (as demonstrated from the X-ray structure of 1), the two Naps units have an orthogonal arrangement that makes them potentially attractive β-turn mimics for incorporation into peptide and polypeptide structures. The ground and the excited state properties of these systems were evaluated in a range of solvents that var…
Solid State Structures of Amide-Substituted 8-Hydroxyquinoline Derivatives
2000
Abstract The amide substituted 8-hydroxyquinoline derivatives 3 and 4 form, in the solid state, hydrogen bonded polymers. Polymeric 3 adopts a helical conformation while 4 forms a double-stranded ladder-type structure.