Diversity-oriented synthesis of pyrazolo[4,3-b]indoles by gold-catalysed three-component annulation: application to the development of a new class of CK2 inhibitors.

Pyrazolo[4,3-b]indole derivatives have been designed as novel CK2 inhibitor compounds based on the binding mode analysis of a previously reported phenylpyrazole-type CK2 inhibitor. A series of pyrazolo[ 4,3-b]indoles and related dihydropyrazolo[4,3-b]indoles were efficiently prepared from simple starting materials using a gold-catalysed three-component annulation reaction as a key step. Several of the newly synthesized compounds displayed high levels of inhibitory activity, indicating that the pyrazolo[4,3-b]indole core represents a promising scaffold for the development of potent CK2 inhibitors.