Synthesis of Cordiaquinones B, C, J, and K on the Basis of a Bioinspired Approach and the Revision of the Relative Stereochemistry of Cordiaquinone C

Four members of the cordiaquinone family (cordiaquinones B, C, J, and K) were synthesized on the basis of a bioinspired scenario in five to six steps from trans,trans-farnesol. As key reactions we used the acid-catalyzed cyclization of a suitable epoxy terpenoid and a Diels−Alder reaction between a diene and benzoquinone. The relative stereochemistry of cordiaquinone C is opposite to that reported in the isolation paper and is in agreement with a plausible scenario for the biosynthesis of cordiaquinones from a common (E)-configurated naphthoquinone epoxide precursor. A fast and clean methodology for the synthesis of the naturally occurring (Z)-β-farnesene from cis-nerolidol is also reported.