The invention relates to azetidin-2-ones of the formula ##STR1## wherein R.sub.a represents hydroxy-lower alkyl, R.sub.1 represents hydrogen, an organic radical bonded by a carbon atom to the ring carbon atom or an etherified mercapto group, R.sub.2.sup.A together with the carbonyl group to which it is attached is a protected carboxyl group and Z' is oxygen, sulfhur or an optionally substituted methylidene group, functional groups in the radicals R.sub.a, R.sub.1 and Z' optionally being in protected form. The azetidinones are useful intermediates for the preparation of penem antibiotics.
本发明涉及公式为##STR1##的氮杂四元酮,其中R.sub.a代表羟基-低碳基,R.sub.1代表氢,有机基团通过碳原子与环碳原子键合或醚化的巯基团,R.sub.2.sup.A与其所附的羰基团一起是受保护的羧基团,Z'是氧、
硫或可选取代的甲基亚烯基团,基团R.sub.a、R.sub.1和Z'中的官能团可选择处于保护形式。这些氮杂四元酮是制备青霉烷类抗生素的有用中间体。