Q is a bond and R1 is lower alkylene; Q, with the 3-position ring carbon of the azetidinone, forms the group ##STR11## wherein preferably R13 and R14 are each ethylene and a and b are each 1, and wherein R12 is ##STR12## Q is a bond and R1 is --O--CH2 --CH(OH)--; Q is a bond and R1 is --CH(OH)--(CH2)2 --; or Q is a bond and R1 is --CH(OH)--CH2 --S(O)0-2 --.