Substituted azetidinone compounds useful as hypocholesterolemic agents

A process for preparing a chiral .beta.-amino ester of the formula ##STR42## wherein:

• Ar.sup.20 is Ar.sup.2, a suitably protected hydroxy-substituted aryl or a suitably-protected amino-substituted aryl;
• Ar.sup.2 is R.sup.4 -substituted aryl;
• Ar.sup.30 is Ar.sup.3, a suitably protected hydroxy-substituted aryl or a suitably-protected amino-substituted aryl;
• Ar.sup.3 is R.sup.5 -substituted aryl;
• R.sup.5 is 1-3 substituents independently selected from the group consisting of --OR.sup.6, --O(CO)R.sup.6, --O(CO)OR.sup.9, --O(CH.sub.2).sub.1-5 OR.sup.9, --O(CO)NR.sup.6 R.sup.7, --NR.sup.6 R.sup.7, --NR.sup.6 (CO)R.sup.7, --NR.sup.6 (CO)OR.sup.9, --NR.sup.6 (CO)NR.sup.7 R.sup.8, --NR.sup.6 SO.sub.2 -lower alkyl, --NR.sup.6 SO.sub.2 -aryl, --CONR.sup.6 R.sup.7, --COR.sup.6, --SO.sub.2 NR.sup.6 R.sup.7, S(O).sub.0-2 -alkyl, S(O).sub.0-2 -aryl, --O(CH.sub.2).sub.1-10 --COOR.sup.6, --O(CH.sub.2).sub.1-10 CONR.sup.6 R.sup.7, o-halogeno, m-halogeno, o-lower alkyl, m-lower alkyl, -(lower alkylene)-COOR.sup.6 and --CH.dbd.CH--COOR.sup.6 ;
• R.sup.4 is 1-3 substituents independently selected from the group consisting of R.sup.5, hydrogen, p-lower alkyl, aryl, --NO.sub.2, --CF.sub.3 and p-halogeno;
• R.sup.6, R.sup.7 and R.sup.8 are independently selected from the group consisting of hydrogen, lower alkyl, aryl and aryl-substituted lower alkyl;
• R.sup.9 is lower alkyl, aryl or aryl-substituted lower alkyl;
• and
• --C(O)OR.sup.10 is an acyl radical of a chiral alcohol of the formula R.sup.10 OH selected from the group consisting of 1-menthyl, isopino-campheyl, (1S)-endo-bornyl, isomenthyl, trans-2-phenylcyclo-hexyl or phenylmenthyl;
• comprising reacting a bromoacetate of the formula R.sup.10 OC(O)CH.sub.2 Br, wherein R.sup.10 OC(O)-- is as defined above, an imine of the formula Ar.sup.20 --N.dbd.CH--Ar.sup.30, wherein Ar.sup.20 and Ar.sup.30 are as defined above, and zinc in an inert solvent at a temperature of 10.degree. to 30.degree. C., optionally in the presence of a zinc activating agent and optionally with ultrasonification.