Synthesis of dysideaproline E using organocatalysis.

(S)-4,4-Dichloro-3-methylbutanoic acid was prepared in 51% overall yield from commercially available starting materials using an organocatalytic transfer hydrogenation to 4,4-dichloro-3-methylbut-2-enal in the key step. The (S)-dichloro acid was used as an intermediate in the first total synthesis of dysideaproline E and a diastereomer confirming the structure of the natural product.