Hyperbranched PEG by Random Copolymerization of Ethylene Oxide and Glycidol

The synthesis of hyperbranched poly(ethylene glycol) (hbPEG) in one step was realized by random copolymerization of ethylene oxide and glycidol, leading to a biocompatible, amorphous material with multiple hydroxyl functionalities. A series of copolymers with moderate polydispersity ( < 1.8) was obtained with varying glycidol content (3–40 mol‐%) and molecular weights up to 49 800 g mol⁻¹. The randomly branched structure of the copolymers was confirmed by ¹H and ¹³C NMR spectroscopy and thermal analysis (differential scanning calorimetry). MTS assay demonstrated low cell toxicity of the hyperbranched PEG, comparable to the highly established linear PEG.

     

Triplex-directed covalent cross-linking of a DNA nanostructure

The triplex approach to DNA recognition is exploited to direct covalent inter-strand cross-links to unique locations within a pre-assembled DNA nanostructure. This approach can be used to improve the stability of DNA nanostructures and demonstrates the feasibility of directing other reactive groups to unique locations within these complexes.     

Scaling and mesostructure of Carbopol dispersions

Rheological measurements were performed on aqueous dispersions of two commercial crosslinked polymer microgels, Carbopol Ultrez 10 and Carbopol ETD 2050, prepared over a wide range of concentration and pH. For all concentrations studied, both the yield stress and the elastic modulus initially increased dramatically with pH and displayed broad peaks at intermediate pH. This is consistent with the onset of jamming of the Carbopol particles due to a rapid increase in particle size caused by osmotic swelling in the presence of NaOH. Scaling of both yield stress and elasticity with concentration was observed only at higher concentrations, which we believe indicates a change from a percolated structure at low volume fractions to a space filling network of compressed particles at high volume fractions. This model is supported by confocal microscopy of fluorescently dyed Carbopol dispersions.     

Polyamide Layer Chromatography. Identification of Amino Acids in Angelica acutiloba Kitagawa via DNP Derivative

Eighteen amino acids; proline, alanine, valine, leucine, isoleucine, hydroxyproline, phenylalanine, ornithine, glycine, serine, aspartic acid, glutamic acid, threonine, asparagine, lysine, tyrosine, tryptophan, and arginine were identified by polyamide layer chromatography via DNP (dinitrophenly) derivatives in Angelica acutiloba Kitagawa (Tang-Kwei)     

Methyl Homologues of Methyl Jasmonate and Methyl Dihydrojasmonate (Hedione®) from Sorbyl Alcohol

Treatment of cycloalkanone dimethyl acetals 3 – 6 with sorbyl alcohol (=(2E,4E)‐hexa‐2,4‐dien‐1‐ol; 1 ) in the presence of acids afforded the novel cycloalkenones 8, 9, 11 , and 13 via a domino reaction (Claisen rearrangement with intramolecular ene reaction and retro‐ene reaction). Cyclopentenone 8 was readily transformed into 14 and 15 , methyl homologues of racemic methyl jasmonate ( 16 ) and methyl dihydrojasmonate (=Hedione®; 17 ), respectively. The organoleptic properties of 14 and 15 are also discussed.     

Eine breit anwendbare Synthese fluoreszierender kondensierter α-Pyrone

In a two step procedure and in usually good yield an -pyrone ring can be annelated to (enolized) cyclic -dicarbonyl compounds like 4-hydroxy-2-pyrones, 4-hydroxycoumarins, 4-hydroxy-2-quinolones and more complex malonylheterocycles, but also to -naphthole.In a first step the combined action of triethyl orthoformate and arylamines upon the dicarbonyl system affords the anilinomethylene derivativesB in usually high yields.B is reacted with an active methylene nitrile (like alkyl cyano-acetates) and one equivalent of a strong base (like sodium methoxide or potassium hydroxide) in a polar aprotic solvent (like dimethylformamide). Subsequent acidification with dilute aqueous acid gives the corresponding -pyroneD with yields from 18 to 84%.The reaction sequence is broadly applicable, which is demonstrated by the synthesis of a series of known (3, 7, 16, 31) and novel (10, 19, 22, 25, 28, 34) heterocyclic systems. Most of them exhibit strong fluorescence in the visible with emission maxima between 450 and 510 nm.

208. Mitt.:H. Wittmann undF. Günzl, Z. Naturforsch.33b, 1540 (1978).