Abstract: 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.

Abstract: The invention relates to a process for obtaining crystals of intermetallic compounds, in particular isolated monocrystals, by cooling alloys in the molten state.The process involves using an alloy in the molten state which has a composition such that the first phase to crystallize during its solidification corresponds to the compound to be isolated, cooling it slowly by subjecting it to cyclic stirring and thermal cycling without attaining the temperature at which another solid phase appears then abruptly expelling the residual liquid.The process is used for obtaining large monophase primary crystals of compounds which melt congruently or incongruently, in particular compounds having symmetry of order 5 known as "quasi-crystals".

Abstract: Compounds of the formula ##STR1## in which R.sub.1 represents lower alkyl substituted by hydroxy or by protected hydroxy, R.sub.2 represents carboxy or functionally modified carboxy, and R.sub.3 represents optionally substituted 3-pyridyl or optionally substituted 4-pyridyl, and pharmaceutically acceptable salts of such compounds, have antibacterial activity. The compounds of the formula I can be manufactured according to processes known per se.

Abstract: The invention relates to 2-penem-3-carboxylic acid compounds of the formula ##STR1## in which R.sub.a represents an organic radical bonded by a carbon atom to the ring carbon atom, a free, etherified or esterified hydroxy or mercapto group or a halogen atom, R.sub.1 represents hydrogen, an organic radical bonded by a carbon atom to the ring carbon atom, or an etherified mercapto group, and R.sub.2 represents a hydroxy group or an R.sub.2.sup.A radical that together with the carbonyl grouping --C(.dbd.O)-- forms a protected carboxyl group, and to salts of such compounds with salt-forming groups, processes for the manufacture of such compounds, pharmaceutical preparations containing compounds of the formula I with pharmacological properties, and their use. The compounds have antibiotic activity.

Abstract: Compounds of the formula ##STR1## in which R.sub.1 is lower alkyl substituted by hydroxy or by protected hydroxy,R.sub.2 represents carboxy or functionally modified carboxy, andR.sub.3 represents amino, lower alkyl-substituted amino, substituted methyleneamino or protected amino,optical isomers of compounds of the formula I, mixtures of these optical isomers, and salts of such compounds of the formula I that have a salt-forming group have antibiotic activity. The compounds of the formula I are manufactured according to processes that are known per se.

Abstract: 2-heterocyclythio-lower alkyl-2-penem compounds of the formula ##STR1## in which R.sub.1 represents hydrogen or methyl, R.sub.2 represents an optionally protected hydroxy group, R.sub.3 represents carboxy or protected carboxy R.sub.3 ', R.sub.4 represents an unsaturated monocyclic heterocyclyl radical that is bonded via a ring carbon atom to the sulphur atom, and m is 2, 3 or 4, and salts of such compounds of the formula I that have a salt-forming group, optical isomers of compounds of the formula I and mixtures of these optical isomers, possess antibiotic properties. The compounds are manufactured according to processes known per se.