Synthetic approaches to the southern part of cyclotheonamide C

A synthetic equivalent of the southern segment of cyclotheonamide C, a cyclopentapeptide isolated from the sponge Theonella, has been synthesized via complementary Wadsworth–Emmons or palladium-catalysed methodologies followed by tandem oxidation/vinylogation in 41% overall yield (five steps) from readily available starting materials.