Enantiomerically pure key intermediates for the synthesis of constanolactones A and B and solandelactones A, B, E and F, the hydroxy-protected (3S,5Z)-undec-1-yn-5-en-3-ol and (3S, 1E,5Z)-1-iodoundec-1,5-dien-3-ol, have been obtained in nine steps starting from (S)-malic acid. (C) 1998 Elsevier Science Ltd. All rights reserved.