Enantioselective Synthesis of a Furan Lignan (+)-Sylvone.

A synthesis of natural tetrahydrofuran lignan (+)-sylvone is achieved starting from methyl allenoate in 5 steps. The synthesis begins from an enantioselective aldol reaction of methyl allenoate with 3,4-dimethoxybenzaldehyde to afford α-addition aldol adduct. Key steps for the synthesis of sylvone include an oxacyclization of the α-hydroxy allenyl adduct followed by a Michael addition of a 1,3-dithiane derivative to establish a sylvone skeleton with suitable stereoselections.