The invention provides a stereselective synthesis method for a lipid-lowering
drug ezetimibe shown in formula I. The method comprises the following steps: a, P-fluorobenzoyl
butyric acid shown in formula II reacts with a
chiral auxiliary shown in formula III to obtain
ketone shown in formula IV; b, under the existence of a chiral catalyst, the
ketone shown in formula IV is reduced to chiral
alcohol shown in formula V; c, chiral
alcohol shown in formula V reacts with a silicyl protective agent to obtain a protected compound shown in formula VI, and then the compound shown in formula VI and
imine shown in formula VII are subjected to addition and protecting groups are removed, so that a compound shown in formula VIII and a
diastereomer thereof shown in formula IX are obtained, and through recrystallization with an appropriate
solvent, an optically pure compound shown in formula VIII is obtained; d, the compound shown in formula VIII is protected with an
acylation reagent, so that a compound shown in formula X is obtained, and
amide shown in formula X is cyclized with a fluorinion catalyst, so that protected
lactam shown in formula XI is obtained; then protecting groups are removed, and the
ezetimibe shown in formula I is obtained.