Novel PARP inhibitor 1 is a promising new candidate for treatment of breast and ovarian cancer. A modified synthetic route to 1 has been developed and demonstrated on 7 kg scale. In order to scale up the synthesis to multikilogram scale, several synthetic challenges needed to be overcome. The key issues included significant thermal hazards present in a Leimgruber–Batcho indole synthesis, a low-yielding side-chain installation, a nonrobust Suzuki coupling and hydrogen cyanide generation during a reductive amination. In addition to these issues, changing from intravenous to oral delivery required a new salt form and therefore a new crystallization procedure. This contribution describes development work to solve these issues and scaling up of the new process in the pilot plant.

The development of a practical, scalable route to PF-00610355 (8) is described. In this convergent approach, amine 9 is coupled to protected bromohydrin 1 to give the doubly protected intermediate 26. TBS-Deprotection of 26 affords the benzyl protected penultimate intermediate 25 which is crystallized as the corresponding hemifumarate salt 25a. On the basis of solubility data, the final debenzylation was conducted in aqueous THF, and the API (8) is isolated from acetonitrile by an unusual distillative crystallization process. The development of an efficient process to prepare amine 9 is also described.

The development and implementation of a scalable process for the manufacture of the Toll-like receptor (TLR7) agonist PF-4171455 (1) is described. Initial routes used to synthesise 1 in milligram quantities were unsuitable for large-scale synthesis to provide bulk material. As part of the transfer between Medicinal Chemistry and Research-API, collaboration provided a fit for purpose route for the kilo-scale synthesis of 1. Key aspects of the synthesis included (i) a safe and practical synthesis of a key nitropyridone intermediate 7 over four steps, (ii) a sequential regioselective chlorination to selectively functionalise 7 and (iii) use of a carbamate as a tethered carbonyl group, allowing an efficient regiospecific synthesis of 1.