Towards a versatile synthesis of kainoids .3. Efficient methods for control of C-4 stereochemistry

Halo- and silenolactonisation methods were used to prepare benzylic lactones from enamide carboxylic acids. The lactones were subsequently cleaved with predominantly inversion of configuration at the benzylic centre to give protected acromelic analogues with the correct C-4 stereochemistry. Hydroxyl directed heterogeneous hydrogenation of related enamide carbinols gave total stereocontrol at C-4. (C) 1997 Elsevier Science Ltd.