The aplyronine C-1-C-11 subunit 4, containing 4 stereocentres and the (E,E)-diene system, was prepared in 7 steps from ethyl ketone (R)-8 using a boron-mediated anti aldol reaction. The corresponding C-15-C-27 subunit 5, containing 6 stereogenic centres and an (E)-alkene, was obtained in 10 steps from ketone (S)-14 using a tin(II)-mediated syn aldol reaction and CBS enone reduction. (C) 1998 Elsevier Science Ltd. All rights reserved.