Stereoselective Synthesis of a Key Precursor of Halicholactone and Neohalicholactone.

An efficient synthesis of a known precursor of halicholactone (1a) and neohalicholactone (1b) has been developed using the strategically functionalized key cyclopropane intermediate 2, which in turn has been synthesized via stereoselective cyclopropanation of trans-cinnamyl alcohol in the presence of the chiral dioxaborolane ligand 4. Elaboration of the above bifunctional cyclopropane to the target molecule was achieved in a relatively short reaction sequence and in good overall yield, representing a formal synthesis of the title compounds.