The design and synthesis of water-soluble analogues of CB30865, a quinazolin-4-one-based antitumor agent

4-[N-[7-Bromo-2-methyl-4-oxo-3,4-dihydroquinazolin-6-ylmethyl]-N-(prop-2-ynyl)amino]-N-(3-pyridylmethyl)benzamide (CB30865) is a quinazolin-4-one antitumor agent whose high growth-inhibitory activity (W1L2 IC50 = 2.8 +/- 0.50 nM) is believed to have a folate-independent locus of action. In addition, CB30865 represents a class of compounds with unique biochemical characteristics such as a delayed, non-phase specific, cell-cycle arrest. The low aqueous solubility of CB30865 prompted a search for more water-soluble analogues for in vivo evaluation of this class of compounds. It was thought that aqueous solubility could be increased by the introduction of amino functionalities at the 2-position of the quinazolin-4-one ring. A variety of compounds (5a-j, 31a-c, 32, and 33) were synthesized in a linear fashion starting from 3-chloro-4-methylaniline. Most of these compounds (e.g., 5a, 5b, 5g) were significantly more water-soluble than CB30865 (636 muM for 5a at pH 6 and 992 muM for 5g at pH 6). In addition, some of them were up to 6-fold more cytotoxic than CB30865 (e.g., for 5a, W1L2 IC50 = 0.49 +/- 0.24 nM) and retained its novel biochemical characteristics.