Search results for "405"
showing 10 items of 3208 documents
Traceless chirality transfer from a norbornene β-amino acid to pyrimido[2,1-a]isoindole enantiomers
2017
Abstract The synthesis of two enantiomeric pairs of pyrimidoisoindoles 9a, 9b and 10a, 10b is reported. During a domino ring-closure reaction, followed by cycloreversion, the chirality of diendo-(−)-(1R,2S,3R,4S)-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide [(−)-1] was successfully transfered to heterocycles (+)-9a, (+)-10a, (−)-9b, (−)-10b and (−)-10c.
Michael additions to double bonds of esters of N-protected (s)-phenylalanyldehydroalanine (X-(s)-Phe-ΔAla-OMe) and its phosphonic acid counterpart (X…
2017
Electrophilic addition of amines, thiols and bromide to the double bonds of model dehydrodipeptides and dehydrophosphonodipeptide was studied. The double bond in these two classes of peptides reacted similarly and gave the same products. These results indicate that dehydropeptides are very good candidates as substrates for modifications of peptide side-chains.
Studies of Nature of Uncommon Bifurcated I–I···(I–M) Metal-Involving Noncovalent Interaction in Palladium(II) and Platinum(II) Isocyanide Cocrystals
2021
Two isostructural trans-[MI2(CNXyl)2]·I2 (M = Pd or Pt; CNXyl = 2,6-dimethylphenyl isocyanide) metallopolymeric cocrystals containing uncommon bifurcated iodine···(metal–iodide) contact were obtained. In addition to classical halogen bonding, single-crystal X-ray diffraction analysis revealed a rare type of metal-involved stabilizing contact in both cocrystals. The nature of the noncovalent contact was studied computationally (via DFT, electrostatic surface potential, electron localization function, quantum theory of atoms in molecules, and noncovalent interactions plot methods). Studies confirmed that the I···I halogen bond is the strongest noncovalent interaction in the systems, followed …
Probing the Folding of Peptide–Polymer Conjugates Using the π-Dimerization of Viologen End-Groups
2020
The synthesis of a foldable viologen-functionalized peptide–polymer conjugate is presented. The ABA-type triblock conjugate with a PEG polymer was capped with a FHFHF pentapeptide sequence and further modified with a viologen building block at both chain ends. The pH-responsive peptide domains fold into an intermediate structure inducing close proximity of the viologen units, which upon a reduction step form π-dimers of the radical cation. Overall the intramolecular folding and intermolecular self-assembly process leads to the formation of supramolecular nanorods. Mixing of viologen-peptide–polymer conjugates with unfunctionalized conjugates leads to crosslinking of the nanorods and hydroge…
N-Alkyl ammonium resorcinarene polyiodides
2016
Four N-alkyl ammonium resorcinarene halides incorporating polyiodides were obtained and structurally analyzed by single crystal X-ray crystallography. The unexpected formation of triiodides and pentaiodide anions in these structures was assumed to be the result of the heterolytic dissociation of molecular iodine (I2) in the presence of electron donors in the N-alkyl ammonium resorcinarene halide system, from which I− further binds one or two I2 molecules resulting in I3− or I5− species, respectively.
Recognition of Viologen Derivatives in Water by N-Alkyl Ammonium Resorcinarene Chlorides
2017
Three water-soluble N-alkyl ammonium resorcinarene chlorides decorated with terminal hydroxyl groups at the lower rims were synthesized and characterized. The receptors were decorated at the upper rim with either terminal hydroxyl, rigid cyclohexyl, or flexible benzyl groups. The binding affinities of these receptors toward three viologen derivatives, two of which possess an acetylmethyl group attached to one of the pyridine nitrogens, in water were investigated via 1H NMR spectroscopy, fluorescence spectroscopy, and isothermal titration calorimetry (ITC). ITC quantification of the binding process gave association constants of up to 103 M–1. Analyses reveal a spontaneous binding process whi…
Efficient energy transfer in a tri-chromophoric dyad containing BODIPYs and corrole based on a truxene platform
2018
A star-shaped molecule was designed and synthesized based on a known central truxene platform. Two BODIPY derivatives and one corrole macrocycle were introduced and connected to the 2, 7 and 12-positions of the truxene unit by Suzuki coupling. The dyad was fully characterized by UV-vis absorption, proton nuclear magnetic resonance, mass spectrometry. The direction of energy transfer upon electronic excitation was explored, and the star-shaped molecule system exhibits a highly efficient photoinduced energy transfer process from the excited BODIPY part to the corrole unit.
Identification of the Iodination and Bromination Products of 3-Hydroxybenzaldehyde: Preparation of 5-Hydroxy-2-iodobenzaldehyde
2017
The monohalogenation products of 3-hydroxybenzaldehyde (1) are useful synthons for the preparation of more complex molecules.1–4 For example, the introduction of a halogen allows the use of a Suzuk...
Post-synthetic methods for functionalization of imidazole-fused porphyrins
2018
Several methods for the post-synthetic modification of imidazo[4,5-[Formula: see text]]porphyrins are reported. First, a synthetic approach to the isomeric difunctionalized porphyrins, containing two [Formula: see text]-fused 2-aryl-1[Formula: see text]-imidazole cycles at adjacent or opposite pyrrole rings of the macrocycle is developed. The core chemistry of this synthetic route is the transformation of 2-aryl-1[Formula: see text]-imidazo[4,5-[Formula: see text]]porphyrins into corresponding imidazodioxochlorins followed by Debus–Radziszewski condensation with aromatic aldehyde. Next, 2-(4-bromophenyl)-1[Formula: see text]-imidazo[4,5-[Formula: see text]]-5,10,15,20-tetramesitylporphyrin…
Iron(III) Chloride as a Mild Catalyst for the Dearomatizing Cyclization of N-Acylindoles
2020
A catalytic approach for the preparation of indolines by dearomatizing cyclization is presented. FeCl3 acts as a catalyst to afford tetracyclic 5a,6-dihydro-12H-indolo[2,1-b][1,3]benzoxazin-12-ones in good yields. The cyclization also proceeds with tosylamides forming C-N bonds in 53% yield.