Wittig-Horner reaction which was modified for poorly reactive systems. This compound was designed to mimic the C-8 carbonium ion formed during SO cyclization. Its inhibitoryactivity on various SO cyclases was evaluated and compared with the 6 Z isomer which has an unfavorable geometry. Only isomer 6 E, the carbocation analogue, was active on SO cyclases from rat liver, pig liver, S. cerevisiae, and C. albicans