A Scalable Process for the Synthesis of the Bcl Inhibitor Obatoclax

Recently we created the novel indolylprodigiosin derivative 2 (obatoclax) and demonstrated its ability to antagonize multiple members of the B-cell lymphoma (Bcl) family of antiapoptotic proteins. The compound has shown potent anticancer activity in several animal tumor models. Obatoclax is now in Phase 1b and 2 clinical trials directed against multiple hematologic and solid tumor malignancies. To support its clinical development, a new scalable synthesis was required. Obatoclax has been prepared using a three-step synthesis, starting from commercially available 4-methoxy-3-pyrrolin-2-one. The reaction sequence involves a haloformylation reaction followed by a Suzuki cross-coupling reaction with an indole-2-boronic acid. The synthesis is completed by an acid-mediated condensation with 2,4-dimethyl-1 H -pyrrole.