Enantioselective Synthesis of the Ethyl Analog of the Marine Alkaloid Haliclorensin C

The enantioselective synthesis (3.7% overall yield in nine steps from 2) and biological screening of the ethyl analog of the macrocyclic marine alkaloid haliclorensin C (compound 5) are reported. Amino alcohol 3, generated by a LiNH(2)BH(3)-promoted reductive ring-opening/debenzylation sequence from phenylglycinol-derived lactam 2, was used as the starting chiral linear building block. Incorporation of the undecene chain via the nosyl derivative 12, methylenation of the pentanol moiety, and a ring-closing metathesis are the key steps of the synthesis.