Search results for "Side chain"
showing 10 items of 345 documents
1,2,4-Oxadiazole rearrangements involving an NNC side-chain sequence.
2009
The thermal rearrangement of N-1,2,4-oxadiazol-3-yl-hydrazones into 1,2,4-triazole derivatives is reported. This represents the first example of a three-atom side-chain rearrangement involving an NNC sequence linked at the C(3) of the oxadiazole. The reactions carried out under solvent-free conditions produced good to high yields of the final products.
ChemInform Abstract: 1,2,4-Oxadiazole Rearrangements Involving an NNC Side-Chain Sequence.
2010
The thermal rearrangement of N-1,2,4-oxadiazol-3-yl-hydrazones into 1,2,4-triazole derivatives is reported. This represents the first example of a three-atom side-chain rearrangement involving an NNC sequence linked at the C(3) of the oxadiazole. The reactions carried out under solvent-free conditions produced good to high yields of the final products.
Removal of Chromophore-proximal Polar Atoms Decreases Water Content and Increases Fluorescence in a Near Infrared Phytofluor
2015
Genetically encoded fluorescent markers have revolutionized cell and molecular biology due to their biological compatibility, controllable spatiotemporal expression, and photostability. To achieve in vivo imaging in whole animals, longer excitation wavelength probes are needed due to the superior ability of near infrared light to penetrate tissues unimpeded by absorbance from biomolecules or autofluorescence of water. Derived from near infrared-absorbing bacteriophytochromes, phytofluors are engineered to fluoresce in this region of the electromagnetic spectrum, although high quantum yield remains an elusive goal. An invariant aspartate residue is of utmost importance for photoconversion in…
Conformational investigation of α,β‐dehydropeptides. XV: N‐acetyl‐α,β‐dehydroamino acid N ′N ′‐dimethylamides: conformational properties from infrare…
2005
The FTIR spectra were analysed in the region of the nu(s)(N-H), AI(C=O) and nu(s)(Calpha=Cbeta) bands for a series of Ac-DeltaXaa-NMe2, where DeltaXaa = DeltaAla, (Z)-DeltaAbu, (Z)-DeltaLeu, (Z)-DeltaPhe and DeltaVal, to determine a predominant solution conformation of these alpha,beta-dehydropeptide-related molecules. Measurements were taken in CCl4, DCM and MeCN solutions. In the same way, spectra of saturated analogues Ac-Xaa-NMe2, where Xaa = Ala, Abu, Leu, Phe and Val, were investigated. To help interpret the spectroscopic results, conformational maps were calculated by the B3LYP/6-31+G** method. Also, the relative energies of all conformers of the dehydro compounds in vacuo as well as…
Crystal structure of the tripeptideN-(benzyloxycarbonyl)glycylglycyl-L-norvaline
2015
The title tripeptide, C17H23N3O6, contains a nonproteinogenic C-terminal amino acid residue, norvaline, which is an isomer of the amino acid valine. Norvaline, unlike valine, has an unbranched side chain. The molecule has a Gly–Gly segment which adopts an extended conformation. The norvaline residue also adopts an extended backbone conformation while its side chain has ag+tconformation. In the crystal lattice, N—H...O and O—H...O hydrogen bonds stabilize the packing. Molecules translated along the crystallographicaaxis associate through an N—H...O hydrogen bond. The remaining three hydrogen bonds are between molecules related by a21screw axis.
A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E
2017
Two hitherto unknown fusaricidins were obtained from fermentation broths of three Paenibacillus strains. After structure elucidation based on tandem mass spectrometry and NMR spectroscopy, fusaricidin E was synthesized to confirm the structure and the suggested stereochemistry. The synthesis was based on a new strategy which includes an efficient access to the 15-guanidino-3-hydroxypentadecanoyl (GHPD) side chain from erucamide.
One-pot synthesis of fluorinated 2-amino-pyrimidine-N-oxides. Competing pathways in the four-atom side-chain rearrangements of 1,2,4-oxadiazoles
2006
Abstract Trifluoromethylated 2-amino-pyrimidine N-oxides have been synthesized by reaction of the 3-amino-5-methyl-1,2,4-oxadiazole with trifluoromethyl-β-diketones in the presence of perchloric acid, followed by hydrolysis. In this ring-to-ring transformation an initial formation of (unisolated) 1,2,4-oxadiazole-pyrimidinium salts, and subsequent ring-opening at the oxadiazole moiety occurs. Isolation of 2-(hydroxyamino)-pyrimidine from the reaction mixture evidenced the presence of a competing pathway where the N(4) nitrogen of the oxadiazole is involved in the formation of a regioisomeric pyrimidinium salt. The effect of the trifluoromethyl group on the product distribution is discussed.…
Optical and electrical properties of oriented thin films of oligomer containing betaine-type moiety in side chain
2005
Non-linear optical and electrical properties of polymer films obtained by dipole orientation of active units are reported. Novel polar oligomer with N-(indan-1,3-dion-2-yl)pyridinium betaine (IPB) as a side group is studied. Orientation of polar groups in oligomer thin films causes an increase of the photo-induced change of surface potential on irradiation in the region of photo-induced electron transfer (PIET) where the IPB group exhibits a reversible change of the value and sign of the dipole moment. At longer wavelengths, the value of the surface potential of the oligomer may be determined by transport of photogenerated charge carriers.
Preparation of Polymeric Nanoparticles by Photo-Crosslinking of an Acryloylated Polyaspartamide in w/o Microemulsion
2004
Biodegradable polymeric nanoparticles have been prepared by UV irradiation of an acryloylated water soluble polymer by an inverse microemulsion. The starting polymer was a α,β‐poly(N‐2‐hydroxyethyl)‐D,L‐aspartamide (PHEA) partially functionalized with glycidyl methacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA‐GMA copolymer obtained (PHG) was crosslinked by UV irradiation of the inverse microemulsion prepared by mixing an aqueous solution of PHG with propylene carbonate (PC)/ethyl acetate (EtOAc) in the presence of sorbitan trioleate (SPAN 85) as surfactant. Nanoparticles obtained were characterized by FTIR spectrophotometry, transmission electron mic…
Physicochemical Properties of A New PEGylated Polybenzofulvene Brush for Drug Encapsulation
2019
A new polymer brush was synthesized by spontaneous polymerization of benzofulvene macromonomer 6-MOEG-9-T-BF3k bearing a nona(ethylene glycol) side chain linked to the 3-phenylindene scaffold by means of a triazole heterocycle. The polymer structure was studied by SEC-MALS, NMR spectroscopy, and MALDI-TOF MS techniques, and the results supported the role of oligomeric initiatory species in the spontaneous polymerization of polybenzofulvene derivatives. The aggregation features of high molecular weight poly-6-MOEG-9-T-BF3k-FE were investigated by pyrene fluorescence analysis, dynamic light scattering studies, and transmission electron microscopy, which suggested a tendency towards the format…