Improved Synthesis of Triketide delta-Lactones from the Pikromycin Biosynthetic Pathway

摘要

In connection with the generation of hybrid polyketide synthases(PKSs)derived from the pikromycin PKS system,we have been interested in delta-lactones 1 and 2.We reported a synthesis of both lactones by the routes based on the asymmetric aldol and the Reformatsky reaction as key steps.Although the desired delta-lactones 1 and 2 were prepared successfully,the synthesis did have limitations.While the delta-lactone 2 was efficiently synthesized by the reported route,the lactone 1 having an epimeric stereochemistry on C-3 could not be prepared efficiently due to the low diastereomeric selectivity in the asymmetric Reformatsky reaction step.