Suppression of epimerization due to selectivity leakage: an application towards the total synthesis of (−)-centrolobine

An InCl3-mediated Prins cyclization of homoallylic alcohols with aldehydes has been established. The enantioselectivities of the trisubstituted tetrahydropyrans are almost retained through the suppression of epimerization. The synthetic value of this protocol is demonstrated by the total synthesis of (−)-centrolobine.