Synthesis, tautomeric states and crystal structure of (Z)-ethyl 2-cyano-2-(3H-quinazoline-4-ylidene) acetate and (Z)-ethyl 2-cyano-2-(2-methyl-3H-quinazoline-4-ylidene) acetate

The new compounds (Z)-ethyl 2-cyano-2-(3H- and 2-methyl-3H-quinazoline-4-ylidene) acetate (1 and 2, respectively) were synthesized by multi-step reactions. The structures in a solution have been determined by (1)H-NMR spectroscopy and in the crystal form by X-ray analysis. Molecule 1 crystallized in a primitive monoclinic cell, space group capital ER, P2(1/c). The cell dimensions are a=7.970(6) A, b=7.061(2) A, c=20.537(7) A, beta=97.69(5) degrees , V=1145.3(10) A(3). Molecule 2 crystallized in a triclinic cell, space group P-1, the cell dimensions are a=8.196(5) A, b=8.997(6) A, c=9.435(4) A, alpha=74.22(4) degrees, beta=89.75(4) degrees , gamma=74.07(5) degrees , V=641.9(6) A(3). In both compounds the presence of intra-molecular NH---O=C hydrogen bonding between the nitrogen atom in position 3 of the quinazoline ring and a carbonyl group of the ethyl cyanoacetate residue was proven by quantum-chemical, (1)H-NMR and X-ray methods.     

Flavone glucosides from Artemisia juncea

A new flavone glucoside, 4′,5-dihydroxy-3′,5′,6-trimethoxyflavone-7-O-β-D-glucoside was obtained from aerial parts of Artemisia juncea, together with the known flavone eupatilin (5,7-dihydroxy-3′,4′,6-trimethoxyflavone). The compounds were comprehensively analytically characterized by IR, UV, NMR and HR-MS, and their chemical structures ascertained. The EtOAc fraction of A. juncea showed the strongest DPPH radical scavenging ability as well as reducing power (in CUPRAC and FRAP assays) and phosphomolybdenum activity. This fraction also exhibited the strongest inhibitory effects on tyrosinase. Additionally, the best antidiabetic effects were observed for eupatilin and the CHCl₃ fraction.     

New polymer syntheses. 102. Aspirin‐modified LC polyesters based on PET and 4‐hydroxybenzoic acid

Four series of liquid‐crystalline copolyesters were prepared by the transesterification of poly(ethylene terephthalate) (PET) with 4‐acetoxybenzoic acid (4‐ABA) or mixtures of 4‐ABA and acetylsalicylic acid (ASA). Two series consisted of 30 mol % PET, and the other two series consisted of 40 mol % PET. The molar ratio of 4‐HBA and ASA was varied in all four series from 0 to 25 mol %. One 30% PET series and one 40% PET series were prepared with the addition of acetic acid, which caused a more perfect randomization of the sequence but yielded slightly lower molecular weights. The incorporation of ASA reduced the crystallinity, which vanished completely at a salicylic acid (SA) content greater than 10 mol %. SA also reduced the stability of the nematic phase, but all the copolyesters were thermotropic up to a 20 mol % SA content. Furthermore, the molecular weights decreased with the increasing incorporation of ASA. Despite this negative trend, the melt viscosity and the storage and loss moduli passed a maximum between 5 and 10% SA. Obviously, the incorporation of SA favored the formation of entanglements. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2013–2022, 2000     

Synthesis of 2‐(2‐hydroxyethyl)‐1‐(2‐hydroxyphenyl)‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline and pseudosymmetry in its crystal structure

Natural and synthetic isoquinoline alkaloids display a wide variety of potent biological activities. The title 1‐aryl‐2‐hydroxyethyl‐1,2,3,4‐tetrahydroisoquinoline, C₁₉H₂₃NO₄, crystallizes with two molecules in the asymmetric unit related by pseudo‐translation but differing only slightly in conformation. The pseudosymmetry is also reflected in the diffraction pattern. The subset of reflections corresponding to the smaller cell and average structure are on average twice as intense as those subtending the larger cell. Tentative refinement in the subcell leads to a disordered structural model with satisfactory agreement factors and, after appropriate use of restraints, acceptable molecular geometry but significantly larger and more anisotropic displacement parameters. In the correct unit cell, the independent molecules differ with respect to the orientation of the hydroxyethyl group. Intramolecular hydrogen bonding occurs between the hydroxyphenyl group and the N atom.