Synthesis and the influence of intramolecular H-bonding in NMR spectra of novel analogs of dendrodoine: Diaminothiazoloylbenzothiazoles

2-(4-Amino-2-arylaminothiazol-5-oyl)benzothiazoles, as the novel analogs of the cytotoxic marine alkaloid dendrodoine, are synthesized and characterized by elemental analysis, IR, NMR and mass spectral data. The thiourea derivatives provide four ring atoms for the thiazole ring construction and thus act as [C–N–C–S] synthons. The remaining carbon of the thiazole is sourced from 2-(2-bromoacetyl)benzothiazoles. This [4+1] heterocyclization reaction is adopted for the synthesis of novel benzothiazole derivatives. The presence of two signals in the ¹H NMR spectrum arising from the NH₂ hydrogens shows that the two hydrogens are not exchanging rapidly on the chemical shift time scale and they are in two different chemical environments due to H-bonding.