Model experiments on the construction of the ABE ring system of hetisine type diterpene alkaloids

The cyanopyridinediols 5 were C‐alkylated to the unsaturated six‐membered imides 6. The allyl derivatives 6c and 6d underwent Cope rearrangement to 8a and 8b, respectively. The latter was transformed to the bromohydrin 9a which, after protection of the hydroxyl group, was cyclized by base to 11a. Removal of the protecting group and oxidation afforded ketone 12, a simple model compound containing the ABE ring system of hetisine type diterpene alkaloids. Its synthesis appears suitable for extensions including the CD ring system.