An approach to the anhydride unit of CP-225,917 and CP-263,114

Compound 1, representing the core structure of CP-225,917, including the anhydride subunit, was prepared by an approach involving siloxy-Cope rearrangement of the strained lactone 18, in which C(15) of the anhydride is already present. The C(14) carbon was introduced at a later stage with the Tebbe reagent. Further elaboration gave homoallylic alcohol 25, which was converted into epoxy aldehyde 27, and then into furan 28. This was transformed efficiently into 1 by the successive action of singlet oxygen, DBU and TPAP.