PROCESS FOR THE PREPARATION OF AN ENANTIOMER OF A BETA-LACTAM DERIVATIVE

There is provided a process for the preparation of an enantiomer of a compound of formula (I) which process comprises separation thereof from a mixture of diastereoisomers of a compound of the formula (I): (I) wherein R is acetyl, alpha -hydroxyethyl or a protected derivative thereof, and R1 and R2 are substituted or unsubstituted hydrocarbon groups, or are joined so as to form a carbocyclic or heterocyclic ring; at least one of R1 and R2 containing a chiral center, such that the enantiomer can be separated thereby; and R3 and R4 are independently hydrogen or an organic group bonded via a carbon atom to the tetrahydro-oxazine ring, or R3 and R4 are joined so as to form together with the carbon atom to which they are attached an optionally substituted C3-7 cycloalkyl or optionally substituted heterocyclyl ring. The enantiomer is of use in the preparation of optically active carbapenem antibiotics.