The production of light by certain marine bacteria of the genus Vibrio has also been demonstrated to be under autoregulatory control. 7V-(3-Oxohexanoyl)-L-homoserine lactone (HSL) has been shownto regulate bioluminescence in Vibrio fischeri8) whilst a closely related molecule, 7V-(3-hydroxybutyryl) homoserine lactone (III) regulates bioluminescence in Vibrio harveyi9). Wehave recently shown that HSLalso regulates the biosynthesis of a carbapenem antibiotic, l-carbapen-2-em-3-carboxylic acid in Erwinia carotovora10) and have furthermore demonstrated its presence in a wide range of terrestrial genera. 1 1} In order to further investigate the role of HSLin the induction of carbapenem biosynthesis and other regulatory processes, a numberof analogues were chemically synthesised and evaluated. AHSL-negative mutant ofE. carotovora ATCC39048 (GSI01) served as the test organism. This paper deals with both the chemical synthesis andbiological evaluation of these compoundsas inducers ofcarbapenembiosynthesis.

Chemistry The autoregulator, HSL and someof its racemic analogues have been previously synthesised by Eberhard et al. i2) to study the mechanism of induction of luminescence in V. fischeri. Our method of synthesis wasa modified procedure of the one reported and is muchsimpler and consistently gives pure compounds in better yields.