Synthetic studies toward highly functionalized 5β-lanosterol derivatives : A versatile approach utilizing anionic cycloaddition

Stereoselective synthesis of the potentially biologically valuable 5β-lanosteroidal-type backbone was achieved via anionic cycloaddition. Synthesis of the two new bicyclic Nazarov intermediates 14 and 40 and their cycloaddition with chiral cyclohexenone 25 and further functional group manipulations resulted in highly functionalized tetracyclic intermediates 28 and 44. These synthetic intermediates could lead to the total synthesis of new lanosterol-based inhibitors.