There is disclosed an azetidinone compound of the formula (I):
##STR1##
wherein R is hydrogen, or a hydroxy protecting group, R.sub.1 and R.sub.2
are each independently alkyl of 1-15 carbon atoms, benzyl or cyclized
together with the carbon atom to which they are attached to form a 5 or
6-membered cyclic hydrocarbon or a heterocyclic radical having one or two
hetero ring atoms, said hetero ring atoms being selected from the group
consisting of O and S; R.sub.3 is lower alkyl or --COO(lower alkyl)
R.sub.4 is phenyl, or phenyl substituted with halogen, lower alkoxy or
nitro which is useful as a synthetic intermediate to the
1'.beta.-methylcarbapenem-type antibacterial agent.
