Challenges with the Synthesis of a Macrocyclic Thioether Peptide: From Milligram to Multigram Using Solid Phase Peptide Synthesis (SPPS).

We describe an optimization and scale-up of the 45-membered macrocyclic thioether peptide BMS-986189 utilizing solid-phase peptide synthesis (SPPS). Improvements to linear peptide isolation, macrocyclization, and peptide purification were demonstrated to increase the throughput and purification of material on scale and enabled the synthesis and purification of >60 g of target peptide. Taken together, not only these improvements resulted in a 28-fold yield increase from the original SPPS approach, but also the generality of this newly developed SPPS purification sequence has found application in the synthesis and purification of other macrocyclic thioether peptides.

CITU: A Peptide and Decarboxylative Coupling Reagent.

Tetrachloro-N-hydroxyphthalimide tetramethyluronium hexafluorophosphate (CITU) is disclosed as a convenient and economical reagent for both acylation and decarboxylative cross-coupling chemistries. Within the former set of reactions, CITU displays reactivity similar to that of common coupling reagents, but with increased safety and reduced cost. Within the latter, increased yields, more rapid conversion, and a simplified procedure are possible across a range of reported decarboxylative transformations.

Dimeric Macrocyclic Antagonists of Inhibitor of Apoptosis Proteins for the Treatment of Cancer.

A series of dimeric macrocyclic compounds were prepared and evaluated as antagonists for inhibitor of apoptosis proteins. The most potent analogue 11, which binds to XIAP and c-IAP proteins with high affinity and induces caspase-3 activation and ultimately cell apoptosis, inhibits growth of human melanoma and colorectal cell lines at low nanomolar concentrations. Furthermore, compound 11 demonstrated significant antitumor activity in the A875 human melanoma xenograft model at doses as low as 2 mg/kg on a q3d schedule.