Total synthesis of antimuscarinic alkaloid, (±)-TAN1251A

The total synthesis of (±)-TAN1251A possessing an antimuscarinic activity was achieved. Carboxylic acid () was converted into carbamate () through a sequence of alkylation and Curtius rearrangement. After a few functional group interconversions of , the corresponding amine () was converted into an azaspiro molecule () through cyclization and installation of a C2 unit. Hydrolysis of followed by lactam formation afforded tricyclic compound (). Coupling of with aldehyde () gave two epimeric adducts, () and (), which were converted into TAN1251A by four steps.