Abstract
Synthesis of the cholestane derivative (V) having a bridged bicyclo [2. 2. 2] octane ring system of the atisine type was attained by various routes starting from 5α-cyanocholestan-3-one (II) as illustrated in Chart 4. The route through the ketal aldehyde (X) and 5α-vinylcholestan-3-one 3-ethylene ketal (XV), the key intermediate for the present synthesis, was found to be most advantageous. However, another route through the bridged acetoxy mesylate (XVI) is also thought to be important, since this intermediate is commonly used for the synthesis of the kaurene-type bridged ring compounds as decribed in the preceding paper. The allylic alcohol function of the atisine type was introduced at the corresponding position with opposite configuration of the hydroxy group giving compound (XXXVIII).
