[2-Amino-3-cyano-dihydroindol-5-ones. 2. The biological activity of a new class of compounds]

Chemical and biological properties of 5-indolones

Indolones of the general formula 1 (Fig. 1 and 2) can act as Michael substrates, which readily add various nucleophiles. 1,4-Addition of S-nucleophiles to these indolones gives access to compounds of the general formula 2 (Fig. 2). The addition is reversible, meaning that these compounds behave as prodrugs of the (in-vitro) cytotoxic indolones. The addition products possess less cytotoxicity of their own, but can presumably release the parent indolones in-vivo. This behaviour makes them valuable compounds, allowing their use as cytotoxic agents. Furthermore, some of the addition products possess antibiotic activity, making them worth testing as agents against certain microbes. Their specificity towards certain microorganisms, which does not fit the usual scheme of activity towards gram positive or gram negative bacteria, is remarkable and needs further verification.

[2-Amino-3-cyano-dihydroindol-5-ones. 3. The chemical reactivity of a new class of compounds]

The chemical reactivity of cytotoxic 5-indolone derivatives is examined in order to get ideas about their behaviour in biological systems. Dienone-phenol-rearrangement preserving the indole ring system could not be achieved, aromatization of 1b gives the phenol derivative 3 alpha. In diluted NaOH ester hydrolysis occurs (1a,b----4a,b). Hydrolysis in conc. H2SO4 yields the amides 5a,b,d. In ethanolic HCl the ammonium salts 6a,b,d are formed. Acylation of 1a to 8 reveals the endocyclic N-atom as the nucleophilic center. Benzaldehyde being a strong electrophile adds to 1b in position 4. Weaker electrophiles such as dimethyl acetylenedicarboxylate (ADC) only react with the amides 5b,d to give 11 and 12. Nucleophiles (water, ethanol, n-propylamine) add to the delta 6-double bond yielding 14-16.