文摘
The synthesis of 4鈥?6鈥?dihydrospiro[piperidine-4,5鈥?pyrazolo[3,4-c]pyridin]-7鈥?2鈥?i>H)-one-based acetyl-CoA carboxylase inhibitors is reported. The hitherto unknown N-2 tert-butyl pyrazolospirolactam core was synthesized from ethyl 3-amino-1H-pyrazole-4-carboxylate in a streamlined 10-step synthesis requiring only one chromatography procedure. The described synthetic strategy provides pyrazolo-fused spirolactams from halogenated benzylic arenes and cyclic carboxylates. Key steps include a regioselective pyrazole alkylation providing the N-2 tert-butyl pyrazole and a Curtius rearrangement under both conventional and flow conditions to install the hindered amine via a stable and isolable isocyanate. Finally, a Parham-type cyclization was used to furnish the desired spirolactam. An analogous route provided efficient access to the related N-1 isopropyl lactam series. Elaboration of the lactam cores via amidation enabled synthesis of novel ACC inhibitors and the identification of potent analogues.