Total Synthesis of Cruentaren A

A triple bypass: The triple bond in the macrolactone ring of 2 served as a lock to prevent the unwanted translactonization to the δ-lactone during the formation of the side chain of the macrolide cruentaren A (1). Subsequent cleavage of the methyl ether and the silicon protecting groups (PG) followed by a Lindlar reduction of the two triple bonds completed the synthesis (see scheme).