Towards the total synthesis of chondrochloren A: synthesis of the ()-enamide fragment.

The stereoselective synthesis of the ()-enamide fragment of chondrochloren () is described. A Buchwald-type coupling between amide and ()-bromide was used to generate the required fragment. The employed amide comprising three chiral centers was obtained through a seven-step sequence starting from ᴅ-ribonic acid-1,4-lactone. The ()-vinyl bromide is accessible in four steps from 4-hydroxybenzaldehyde. The pivotal cross coupling between both fragments was achieved after extensive experimentation with copper(I) iodide, KCO and ,'-dimethylethane-1,2-diamine.