合成路线1

Alkylation of the dianion of azetidinonecarboxylic acid (I) with 2-ethoxybenzyl bromide (II) in cold THF affords (III). Oxidative cleavage of the carboxyl group of (III) using lead tetraacetate and HOAc provides the acetate ester (IV), which is desilylated to (V) with tetrabutylammonium fluoride in THF. Azetidinone (V) is coupled with benzhydryl 4-hydroxybenzoate (VI) to yield ether (VII). Curtius rearrangement of carboxylic acid (VIII) provides isocyanate (IX). Coupling between isocyanate (IX) and azetidine (VII) gives rise to urea (X). The benzhydryl ester group of (X) is finally cleaved by treatment with trifluoroacetic acid in the presence of anisole.