Q is a bond and R1 is lower alkylene; Q, with the 3-position ring carbon of the azetidinone, forms the group wherein preferably R13 and R14 are each ethylene and a and b are each 1, and wherein R12 is 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???.