The mechanistic target of rapamycin (mTOR) plays a pivotal role in growth and tumor progression and is an attractive target for cancer treatment. ATP-competitive mTOR kinase inhibitors (TORKi) have the potential to overcome limitations of rapamycin derivatives in a wide range of malignancies. Herein, we exploit a conformational restriction approach to explore a novel chemical space for the generation of TORKi. Structure–activity relationship (SAR) studies led to the identification of compound 12b with a ∼450-fold selectivity for mTOR over class I PI3K isoforms. Pharmacokinetic studies in male Sprague Dawley rats highlighted a good exposure after oral dosing and a minimum brain penetration. CYP450 reactive phenotyping pointed out the high metabolic stability of 12b. These results identify the tricyclic pyrimido-pyrrolo-oxazine moiety as a novel scaffold for the development of highly selective mTOR inhibitors for cancer treatment.

A new, scalable, rapid, high yielding, and practical synthesis of 4-(difluoromethyl)­pyridin-2-amine provides a key intermediate for the preparation of numerous protein kinase inhibitors and clinical candidates targeting phosphoinositide 3-kinase (PI3K) and the mechanistic target of rapamycin (mTOR) kinase. Starting from 2,2-difluoroacetic anhydride, an efficient five-step and two-pot procedure to prepare 4-(difluoromethyl)­pyridin-2-amine (1) has been developed. Noteworthy aspects of this strategy include the avoidance of an amination process using a sealed vessel. Each step of the synthetic route has been optimized, and key intermediates have been isolated and characterized prior to the final two-pot procedure, which has been successfully applied for large-scale production.