Synthesis and X-ray structures of new cycloalka[e]pyrano[2,3-b]pyridine derivatives: novel tacrine analogues

"One-pot" access to dihydrofurans via tandem oxidative difunctionalization and ring contraction of aminopyrans

An operationally simple and efficient protocol for the construction of dihydrofuran derivatives has been accomplished via a sequential addition of N-chlorosuccinimide and a base to 2-amino-4H-pyran derivatives in alcohol medium. The one-pot protocol proceeding via tandem oxidative difunctionalization and ring contraction provides an entirely new strategy for the construction of the dihydrofuran skeleton.

7-Methoxy-2-phenylquinoline-3-carbaldehyde

In the title mol­ecule, C₁₇H₁₃NO₂, the phenyl ring is inclined to the quinoline ring system by 43.53 (4)°. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming double-stranded chains propagating along [011]. These chains are linked via π–π inter­actions involving inversion-related quinoline rings; the shortest centroid–centroid distance is 3.6596 (17) Å.

2-p-Tolyl-2,3-di-hydro-quinolin-4(1H)-one

In the title mol­ecule, C₁₆H₁₅NO, the tetra­hydro­pyridine ring is in a sofa conformation with the methine C atom forming the flap. The dihedral angle between the benzene rings is 80.85 (8)°. In the crystal, mol­ecules are arranged in alternating double layers parallel to (100) and are connected along [001] by N—H⋯O hydrogen bonds. In addition, weak C—H⋯π inter­actions are observed.

Purification of acetylcholinesterase by 9-amino-1,2,3,4-tetrahydroacridine from human erythrocytes

The acetylcholinesterase enzyme was purified from human erythrocyte membranes using a simple and effective method in a single step. Tacrine (9-amino-1,2,3,4-tetrahydroacridine) is a well-known drug for the treatment of Alzheimer's disease, which inhibits cholinesterase. We have developed a tacrine ligand affinity resin that is easy to synthesize, inexpensive and selective for acetylcholinesterase. The affinity resin was synthesized by coupling tacrine as the ligand and L-tyrosine as the spacer arm to CNBr-activated Sepharose 4B. Acetylcholinesterase was purified with a yield of 23.5 %, a specific activity of 9.22 EU/mg proteins and 658-fold purification using the affinity resin in a single step. During purification, the enzyme activity was measured using acetylthiocholine iodide as a substrate and 5,5'-dithiobis-(2-nitrobenzoicacid) as the chromogenic agent. The molecular weight of the enzyme was determined as about 70 kDa monomer upon disulphide reduction by sodium dodecyl sulphate polyacrylamide gel electrophoresis. K(m), V(max), optimum pH and optimum temperature for acetylcholinesterase were found by means of graphics for acetylthiocholine iodide as the substrate. The optimum pH and optimum temperature of the acetylcholinesterase were determined to be 7.4 and 25-35 °C. The Michaelis-Menten constant (K(m)) for the hydrolysis of acetylthiocholine iodide was found to be 0.25 mM, and the V(max) was 0.090 μmol/mL/min. Maximum binding was achieved at 2 °C with pH 7.4 and an ionic strength of approximately 0.1 M. The capacity for the optimum condition was 0.07 mg protein/g gel for acetylcholinesterase.

3-(1H-1,3-Benzimidazol-2-yl)-2,7-dimethoxyquinoline

In the title mol­ecule, C₁₈H₁₅N₃O₂, the dihedral angle between the quinoline and benzimidazole ring systems is 23.57 (5)°. The C atoms of the meth­oxy groups are both close to being coplanar with their attached ring systems [deviations = 0.193 (2) and −0.020 (2) Å]. An intra­molecular N—H⋯O hydrogen bond closes an S(6) ring. In the crystal, N—H⋯N hydrogen bonds link the mol­ecules into C(4) chains propagating in [010]. Weak C—H⋯π inter­actions also occur.