MAPT and early-onset autosomal dominant Alzheimer disease: Finally, the synthesis of [18F]T807, a PET tau tracer for Alzheimer disease was reported by Zheng et al. [77] The authors proposed a reaction scheme starting with the Stille coupling of 5-bromo-2-nitropyridine 109 with 7-bromo-5H-pyrido[4,3-b]indole 124, followed by Boc protection (Scheme 42).