Abstract: A compound of formula (I) ##STR1## is prepared by cyclizing a compound of formula (IIa) or (IIb) or a mixture thereof ##STR2## wherein X is hydroxyl or halogen and R.sup.1 and R.sup.2 independently, represent hydroxy protecting groups) followed by removal of the protecting groups R.sup.1 and R.sup.2.The compound (I) is of use as an intermediate in the stereoselective preparation of (.+-.) trans-5-fluoro-2,3,3a,9a-tetrahydro-1H-[1,4]benzodioxino[2,3-c] pyrrole, which is a selective .beta..sub.2 -adrenoreceptor antagonist and is thus of potential value, in particular, for the treatment or prevention of depression.

Abstract: The invention provides crystalline ethyl (Z)-2-hydroxyimino-2-(2-triphenylmethylaminothiazol-4-yl)acetate hydrochloride N,N-dimethylformamide solvate which is of value as an intermediate in the preparation of .beta.-lactam antibiotics such as ceftazidime, azthreonam, cefmenoxime, cefotaxime, ceftriaxon, ceftizoxime and cefodizime.

Abstract: The invention provides crystalline (Z)-2-(2-t-butoxycarbonyl-prop-2-oxyimino)-2-(2-triphenylmethylaminothiazo l-4-yl)acetic acid in association with dioxan and its crystalline ethyl ester in association with methanol. The compounds are of value as intermediates in the preparation of .beta.-lactam antibiotics such as ceftazidime or azthreonam.

Abstract: The invention provides crystalline ethyl (Z)-2-hydroxyimino-2-(2-triphenylmethylaminothiazol-4-yl)acetate hydrochloride N,N-dimethylformamide solvate which is of value as an intermediate in the preparation of .beta.-lactam antibiotics such as ceftazidime, azthreonam, cefmenoxime, cefotaxime, ceftriaxon, ceftizoxime and cefodizime.

Abstract: The invention provides crystalline (Z)-2-(2-t-butoxycarbonyl-prop-2-oxyimino)-2-(2-triphenylmethylaminothiazo l-4-yl)acetic acid in association with dioxan and its crystalline ethyl ester in association with methanol. The compounds are of value as intermediates in the preparation of .beta.-lactam antibiotics such as ceftazidime or azthreonam.

Abstract: (6R,7R)-7-[(Z)-2-(2-Aminothiazol-4-yl)-2-(2-carboxyprop-2-oxyimino)acetamid o]-3-(1-pyridiniummethyl)ceph-3-em-4-carboxylate in the form of its crystalline pentahydrate. This pentahydrate has a well defined crystalline structure and exhibits good stability on storage. The pentahydrate exhibits excellent antibiotic activity, particularly against organisms which are normally difficult to combat with .beta.-lactam antibiotics.