Synthesis and In vitro Antitumor Screening of Novel 2,7-Naphthyridine-3-carboxylic Acid Derivatives

New derivatives of 2,7-naphthyridine-3-carboxylic acid were synthesized. We report the hydrolysis, chlorination, alkylation, and amination of the 2,7-naphthyridine esters 1, 2. A series of Schiff's bases 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h, 8i, 8j, 9a, 9b, 9b', 9c, 9d, 9e were produced by treating the obtained hydrazides 6 and 7 with aromatic aldehydes. The anticancer activities of the obtained derivatives were examined. Eighteen of the 24 newly synthesized compounds were qualified by the National Cancer Institute NCI (Bethesda, MD, USA) for in vitro screening against 60 different human tumor cell lines. The most active compound 8i was evaluated against a 60-cell panel at five concentration levels and proved to be most sensitive towards central nervous system cancer (SF-539), with GI50=0.70 mu mol, total growth inhibition=5.41 mu mol, and LC50=53.7 mu mol.