Enantioselective Formal Total Synthesis of Damsin

Enantioselective formal total synthesis of damsin, which was isolated from Compositae Ambrosia maritima L., is described. The highly enantio- and diastereoselective catalytic Mukaiyama.Michael reaction and subsequent highly stereoselective epimerization shorten the synthetic steps. It is also reported that the enolate, which was formed by the reaction of β-keto sulfone with lithium naphthalenide, reacted with methyl cyanoformate to form a quaternary stereogenic center in high yield with high stereoselectivity. This finding extends the synthetic chemistry starting from β-keto sulfones.