Design, synthesis and anti-tumor activities of carbamate derivatives of cinobufagin.

A series of cinobufagin-3-yl nitrogen-containing-carbamate derivatives were designed, synthesized, and evaluated for their proliferation inhibition activities. The structure-activity relationships suggested that the substituents at C-16 was a crucial factor for the potency and that follows this trends: acetic ester ≫ benzoic ester ≈ hydroxy > carbamate. Compounds 3f, 3g, 3h, and 3i exhibited significant in vitro antiproliferative activities against the eight tested tumor cell lines, with IC50 values ranging from 8.1 to 237.4 nM. Furthermore, 3g tartrate (3g-TA) significantly inhibited tumor growth by 64.5%, 83.9%, and 93.0% at a doses of 4, 6, 8 mg/kg/qod by ip, respectively.