Indolizomycin is a potent antibiotic agent produced by a microorganism called SK2-52. Of particular interest is the fact that SK2-52 is a mutant microorganism that was created in a laboratory from two different strains, Streptomyces teryimanensis and Streptomyces grisline, neither of which is antibiotic producing. This raises the possibility of using mutant microorganisms as factories for producing novel structures with a variety of medicinal properties. During S. J. Danishefsky’s synthesis of racemic indolizomycin, compound 1 was treated with triphenylphosphine (PPh3) to afford compound 2 (J. Am. Chem. Soc. 1990, 112, 2003–2005). The reaction between 2 and 3 then gave compound 4. These processes are believed to proceed via the following intermediates. Complete the mechanism by drawing all curved arrows and identify the arrow-pushing pattern employed in each step.