Early routes to STX from Jacobi and Kishi 16 featured a rapid entry to the carbon skeleton but required numerous corrective redox manipulations. The 2006 Du Bois approach to STX features a unique C-H amination and macrocyclic ring closure while their 2008 approach utilizes an embedded pyrrole that can be manipulated to the product after redox manipulations . Nagasawa's entry to STX builds complexity rapidly through a dipolar cycloaddition but is plagued with difficulties in installing the requisite guanidium residues .