Six azocalix[4]arenes were synthesized for the first time by diazo-coupling reactions with calix[4]arene. The products showed unusual spectral properties including an azophenol–quinine–hydrazone tautomerism. Owing to the chromophoric nature, the four pKa’s for water-soluble p-(4-trimethylammoniopheylazo)calix[4]arene could be determined to be 0.5, 2.0, 10.0, and ca. 13. The marked pKa split was explained by the strong hydrogen-bonding interactions characteristic of calix[4]arene.

Diazo coupling between calix[4]arene and five substituted benzenediazonium ions in tetrahydrofuran at 5 "C in the presence of pyridine afforded the tetrasubstituted calixC43arenes as main products and small amounts of mono-, di-and tri-substituted calix [4]arenes even in the presence of unchanged calix[4]arene: the unusual autoaccelerative substitution reaction is attributed t o the specific hydrogenbonding effect among the calix[4]arene OH groups. The products were applied as new 'chromophoric calix[4]arenes,' which selectively recognised Li'.

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A series of 4 beta-alkyl (7-10), 4 beta-aminoalkyl (12a-y), and 4 beta-amidoalkyl derivatives (14a-g) of 4'-O-demethyl-4-desoxypodophyllotoxin have been synthesized, and their cytotoxicity, inhibition of DNA topoisomerase II (Topo II), and tubulin polymerization were evaluated. All derivatives of 12a-y and 14a-g did not inhibit tubulin polymerization. Many compounds exhibited cytotoxicity and inhibition of Topo II. In particular, 12o, 12s, 12t, and 12u strongly inhibited Topo II (IC50 (microM) 32.5, 60.9, 58.8, and 33.6, respectively) and were strong cytotoxicity against P388 cells (IC50 (M) 1.0, 4.1, 3.3, and 3.0 x 10(-9), respectively), compared with VP-16 (IC50 (microM) 59.2, IC50 (M) 1 x 10(-8), respectively). These compounds were nearly equal to or superior to VP-16 in antitumor activity in vivo (L1210, P388, and Lewis lung) and were more cytotoxic against various human cell lines in vitro than VP-16.

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