Abstract: Compounds of formula (I): 1

Abstract: A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: ##STR1## wherein R represents an alkyl or aralkyl group, substituted on an alkyl carbon atom other than that adjacent to --NH-- group, with one or more functional groups selected from halogen, non-aromatic heterocyclyl linked through carbon, aromatic heterocyclyl, nitro, oxo, --OR.sup.1, SR.sup.1 --P(O)R.sup.2 R.sup.3, --NR.sup.4 R.sup.5, .dbd.NR.sup.6, or a sulphur linked organic radical, wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are various organic radicals.Processes for the preparation of these compounds and pharmaceutical compositions containing them are also disclosed.

Abstract: The invention provides the compound (2R,5R,Z)-3-(2-hydroxyethylidene)-7-oxo-4-oxa-1-azabicyclo-[3,2,0]heptane- 2-carboxylic acid and its salts in purified form and pharmaceutical compositions containing them and a process for the purification of such compounds by conversion in aqueous media to the lithium salt of the above acid and precipitation thereof.

Abstract: A compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof: ##STR1## wherein R.sup.1 is phenyl, 4-hydroxy phenyl, 3,4-dihydroxyphenyl, 3,4-diacetoxyphenyl or a 5- or 6- membered heterocyclic ring containing up to three heteroatoms selected from oxygen, sulphur or nitrogen, optionally substituted with hydroxy, amino, halogen or C.sub.1-6 alkoxy; and R.sup.2 is a sub-group of formula (A):--NH--R.sup.3 (A)wherein R.sup.3 is an optionally substituted C.sub.1-10 alkyl or C.sub.3-7 cycloalkyl group; or R.sup.2 is a sub-group of formula (B):--NH--CO--R.sup.4 (B)wherein R.sup.4 is an aryl group, an optionally substituted C.sub.1-10 alkyl group or a C.sub.1-6 alkyloxy group optionally substituted by an aryl group.