Proposed biosynthetic intermediates of a marine monocyclic ether alkaloid, brevisamide (1) were synthesized for biosynthetic studies on the marine ladder-frame polyethers. The intermediates comprising a linear backbone with trans-olefin (2) and epoxide (3) functionality were synthesized via a Suzuki-Miyaura cross coupling reaction and a Katsuki Sharpless asymmetric epoxidation reaction. In protic solvents, 3 was unstable and readily cyclized to an unnatural 5-membered ether ring compound (4).