Absolute Configuration of Multifidene and Viridiene, the Sperm Releasing and Attracting Pheromones of Brown Algae

The absolute configurations of the two algal pheromones multifidene 1 and viridiene 2 were determined as (+)‐(3 S , 4 S )‐3‐[( Z )‐1‐butenyl]‐4‐vinylcyclopentene and (+)‐(3 R , 4 S )‐3‐[(1 Z )‐1, 3‐butadienyl]‐4‐vinylcyclopentene, respectively. The strategy involves enzyme‐initiated asymmetric synthesis of the ring‐saturated pheromone analogues (+)‐ 8a and (−)‐ 8b and their subsequent catalytic hydrogenation to the chiral cycloalkanes 9a and 9b , only the letter of which is also obtained from the two natural messengers (+)‐ 1 or (+)‐ 2 . Biological activity assays proved these enantiomers of 1 or 2 to be the characteristic pheromones for male gametes of the seaweeds Syringoderma , Cutleria multifida and Chorda tomentosa .