Abstract: 2-Vinylclavem compounds are disclosed which have been found of value in the synthesis of thio-derivatives of clavulanic acid which possess antibiotic and .beta.-lactamase inhibitory activity. Methods for preparing the vinylclavem compounds are disclosed and processes for preparing the thio-derivatives are given.

Abstract: Antibiotic compounds of the general formula ##STR1## [wherein R is a phenyl, thienyl or furyl group; R.sup.a and R.sup.b, which may be the same or different, are each selected from hydrogen, C.sub.1-4 alkyl, C.sub.2-4 alkenyl, C.sub.3-7 cycloalkyl, phenyl, naphthyl, thienyl, furyl, carboxy, C.sub.2-5 alkoxycarbonyl and cyano, or R.sup.a and R.sup.b together wth the carbon atom to which they are attached form a C.sub.3-7 cycloalkylidene or cycloalkenylidene group; R.sup.c and R.sup.d, which may be the same or different, each represents a hydrogen atom or a substituting group e.g. an alkyl group or substituted alkyl group; or R.sup.c and R.sup.d together with the nitrogen atom to which they are attached form a saturated or unsaturated heterocyclic ring which contains 5-7 ring members and which may contain additional hetero atoms, and may be substituted by lower alkyl; R.sup.e represents hydrogen or C.sub.