Synthesis of dimeric spirostanols linked through a 1,4-dimethylidenebenzene moiety by double BF 3 ·Et 2 O-catalyzed aldol condensation of steroid sapogenins and terephtalaldehyde.

BF ₃ ·Et ₂ O-catalyzed double aldol condensation between acetylated steroid sapogenins and terephtalaldehyde led to acetylated dimeric spirostanols linked through a 1,4-dimethylidenebenzene moiety in moderate to good yields. The E configurations of the introduced double bonds were corroborated by NOE experiments. Saponification of the dimeric steroids led to the corresponding dimeric spirostanols.
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