| Abstract: | A New Synthesis of (±)-Dihydrorecifeiolide Ethyl 1-(2′-formylethyl)-2-oxocyclooctane-1-carboxylate ( 2 ) prepared by Michael reaction of ethyl 2-oxocyclooctane-1-carboxylate ( 1 ) was regioselectively methylated at the aldehyde group with (CH3)2TiOCH(CH3)2]2 to give 3 (Scheme 1). The alcohol 3 was treated with Bu4NF to give the deethoxycarbonylated product 4 which by distillation gave the bicyclic enol ether 5 . Oxidation (m-chloroperbenzoic acid) of 5 and reduction of the resulting oxolacton 6 yielded the title compound (±)-dihydrorecifeiolide ( 7 ) in an overall yield of nearly 50 %. Methylation of the aldehyde 2 with MeLi gave the ring-enlarged lacton 9 in poor yield (13 %). The deethoxycarbonylation reaction 3 → 4 was studied in more detail (Scheme 3). |
