Yoshiharu Nawata

Reactions of 3-substituted quinoline 1-oxides with acylating agents

Reactions of 3-fluoro- (1a), 3-bromo- (1b), 3-methyl- (1c), 3-methoxy- (1d) and 3-acetamidoquinoline 1-oxides (1e) with acylating agents (POCl 3 , Ac 2 O, TsCl and PhCOCl) were examined (table). While only 2-substituted quinolines were obtained from 1a and 1b, fair amounts of 4-substituted products were formed in reactions of 1d, the sole formation of the 4-acetoxyquinoline (6) with Ac 2 O being the most significant result. 2-Chloroquinoline, 4-chloroquinolines and 2-tosyloxyquinolines were formed (and sometimes predominate) in addition to 2-quinolinones in reactions with TsCl

New cyclization reactions of 3-dialkylamino-4-amino-pyridines under conditions of nitration

Treatment of 3-dialkylamino-4-aminopyridines (1) with nitric and sulfuric acids affords imidazo-[4,5-c] pyridine derivatives (2, 3 and 4) and 1,2,3- triazolo [4,5-c] pyridine 2-oxides (5) by cyclization reaction of the corresponding 4-nitroaminopyridines

The conformation of the macrotetrolide ring system from X-ray and molecular mechanics studies

Abstract X-ray data of four compounds of nactins (nonactin, dinactin, tetranactin in free and complex forms) were analysed by molecular mechanics in order to study the stability of the conformations of the macrotetrolide antibiotics (ionophoric substance). Starting with the X-ray data, the four types of conformation were converged to the respective minimum energy structures. The complex type conformation (approximate S4 symmetry) has the lowest initial and final steric energy. However, the vicinal H-H coupling constants of the complex type conformation, calculated for the minimum energy structure by the Karplus formula, are not in accordance with the published data for nonactin in acetone-d6 and for tetranactin in CDCl3 solutions. The dinactin type conformation (asymmetric) has the largest dipole moment, which may be the most favorable one to take the cations in the molecule.

Reaction of 2-bromo-2,3-dihydro-1H-pyrazolo[1,2-a]indazolium bromides with alkaline solution

Obtention de bromures de 9H-pyrazolo [1,2-a] indazoliums qui sont ensuite debromhydrates en pyrazolo [1,2-a] indazoles

X-Ray crystallographic determination of the molecular structures of the antibiotic cyanocycline A and related compounds

The molecular structures and absolute configurations of cyanocycline A (I) and related compounds have been determined by single crystal X-ray diffraction methods using diffractometer-measured data. Compound (I) contains the molecular structure of naphthyridinomycin with a hydroxy-group replacing a cyano-group. When the pH at which crystallization is carried out is changed, the oxazolidine ring of (I) changed reversibly from the closed to the open form in the bis(hydrogen halide) salts. Two nitrogen atoms are quaternized in the bis(hydrogen halide) salts: one forms an ion-pair with a halide anion and the other has a short intramolecular contact with the oxygen of atom the hydroxymethyl group. The remaining halide anion in these salts forms a bifurcated intermolecular hydrogen bond with two hydroxy groups.