合成路线1

The chiral intermediate (X) is prepared by two methods. Treatment of lactonitrile (I) with HCl/EtOH affords imidate (II), which is further reacted with ethanolic ammonia to produce amidine (III). Claisen condensation between ethyl acetate (IV) and ethyl formate (V) in the presence of NaH provides the sodium salt of ethyl 3-hydroxyacrylate (VI). Cyclization of (VI) with amidine (III) then furnishes the racemic pyrimidinone (VII). Kinetic resolution of (VII) is accomplished by acylation with vinyl butyrate (VIII) in the presence of lipase P30 to yield a mixture of unreacted (S)-alcohol (IX) and the desired (R)-butyrate ester (X), which can be separated by partition between CH2Cl2 and H2O.