However, its absolute stereochemistry could not be elucidated due to the scarcity (0.3 mg) of the sample. To clarify the complete stereochemistry of 1, we carried out the first total synthesis of koshikalide (1)
a 14-membered macrolide that exhibits moderate cytotoxicity, was isolated from a marine cyanobacterium and its relative stereochemistry was established on the basis of spectroscopic analyses.
structure by a nonbasic lactonization method using a Mitsunobu reaction. Based on this previous knowledge, we envisioned the retrosynthesis of koshikalide (1) as follows