(-(3S,4S)-3-BUTYL-4-VINYLCYCLOPENTENE IN BROWN-ALGAE OF THE GENUS DICTYOPTERIS())

(-)-(3R,4R)-3-Butyl-4-vinylcyclopentene [(-)-1] was synthesized via ()-(1S,5R)-3-oxabicyclo [3,3,0] oct-6-en-2-one. Synthetic (-)-1 coincid ed with the peak with later retention time of racemic (+/-)-1 in a chi ral GC (CP-Cyclodex 236M), while the natural 1 in essential oils from the marine brown algae, Dictyopteris prolifera and D. sp. was identica l with the earlier retention time peak. Thus, the absolute configurati on of the natural product in Dictyopteris oils was determined as (+)-( 3S,4S) with ca 100% enantiomeric excess. (C) 1997 Elsevier Science Ltd .