The synthesis of a 28-membered thiopeptide macrocycle is described. Key steps are mild aza-Wittig thiazole ring closures, a scandium(III)-mediated regioselective ester hydrolysis, and a highly efficient macrolactam formation with its 3-hydroxypyridine nucleus orthogonally protected.
Key words
antibiotics - aza-Wittig reaction - heterocycles - natural products - macrocyclization - thiopeptides.