The first total synthesis of AB-ring system of an antiproliferative and cyt
otoxic 9,11-secosterol 1 is described. Enantiomerically pure (3S,5S,6S,10S)
-3,6-diacetoxy-10-methylbicyclo[4.4.0]- decan-9-one 8 (steroidal numeration
) was prepared from (S) Wieland-Miescher ketone.