Evaluation of asymmetric Diels–Alder approaches for the synthesis of the cyclohexene subunit of CP-225,917 and CP-263,114

Asymmetric synthesis of a functionalised cyclohexenone required for total synthesis of CP-225,917 and CP-263,114 is reported, using a Lewis acid-promoted Diels–Alder reaction between a 2-silyloxy-1,3-diene and a dienophile bearing an oxazolidinone auxiliary. A novel method for appendage of the exocyclic malonate unit, via cyclopropane ring opening, is also described.