1,5-Naphthyridines and their n-oxides III. Synthesis and biological activity of some mono- and disubstituted 1,5-naphthyridines and their n-oxides
In order to search for biologically active compounds in the 1,5-naphthyridine series, we synthesized 2-mercaptoand 2-(4'-aminobenzenesulfonamido)-l,5naphthyridines and some of their 6-substituted derivatives. 2-(4'-Aminobenzenesulfonamido)-l,5-naphthyridine (I) was obtained by reaction of 2-amino-l,5naphthyridine with 4-carbomethoxyaminobenzenesulfonyl chloride in pyridine with subsequent saponification of the carbomethoxy group in the resulting 2-(4'carbomethoxyaminobenzenesulfonamido)-l,5-naphthyridine (II).
Tautomerism in side-chain derivatives of n-heterocycles
Abstract NMR and UV spectra of some α (ψ)cyano-, carbethoxy-, and acylmethyl derivatives of 2-oxo-1,2-dihydroquinoxaline, 2-oxo-1,2-dihydro-6,7-benzoquinoxaline, 3,4-dihydro-1,4,2H-benzoxazone, quinaxoline, and quinoline, were recorded in chloroform, dimethyl sulfoxide, and trifluoro- acetic acid. The results indicate the existence of tautomeric equilibria, with noticeable contribution of the enaminic structures B or D, depending on the solvent and the nature of the heterocycle. Relationhips between some NMR parameters and tautomeric structures were observed.
Über Protonenresonanz-Spektren von Pteridinen III. Zur Struktur von 9-Acetonylxanthopterin und Erythropterin
Proton magnetic resonance spectra of 9-acetonylxanthopterine (I) and erythropterine (II) are reported. Based upon these data and UV.-spectroscopic evidence, it is shown that these compounds exist in the tautomeric forms Ib and IIb, respectively.