Discovery of the 3-Imino-1,2,4-thiadiazinane 1,1-Dioxide Derivative Verubecestat (MK-8931)-A ß-Site Amyloid Precursor Protein Cleaving Enzyme 1 Inhibitor for the Treatment of Alzheimer's Disease.

Verubecestat 3 (MK-8931), a diaryl amide-substituted 3-imino-1,2,4-thiadiazinane 1,1-dioxide derivative, is a high-affinity ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitor currently undergoing Phase 3 clinical evaluation for the treatment of mild to moderate and prodromal Alzheimer's disease. Although not selective over the closely related aspartyl protease BACE2, verubecestat has high selectivity for BACE1 over other key aspartyl proteases, notably cathepsin D, and profoundly lowers CSF and brain Aß levels in rats and nonhuman primates and CSF Aß levels in humans. In this annotation, we describe the discovery of 3, including design, validation, and selected SAR around the novel iminothiadiazinane dioxide core as well as aspects of its preclinical and Phase 1 clinical characterization.

A concise palladium-catalyzed carboamination route to (+/-)-tylophorine.

A total synthesis of the racemic natural product tylophorine [(+/-)-1] has been demonstrated using the palladium-catalyzed carboamination method developed by Wolfe and co-workers. In this case, an electron-rich aryl bromide 18 was prepared in four steps and subjected to palladium-catalyzed Wolfe carboamination conditions with olefinic carbamate 7 to provide the racemic 2-(arylmethyl)pyrrolidine (+/-)-19 in good yield and was further elaborated to racemic tylophorine. This application of the Wolfe carboamination protocol as a key step to construct a natural product provides further evidence of the utility of the method.