Triethylamine (0.3 ml) was added to a stirred suspension of ampicillin (0.7 g) in anhydrous DMF (120 ml) under a nitrogen atmosphere. To the resultant clear solution was added z,z,z-octadeca-6,9,12-trienoic acid, N-hydroxysuccinimide ester (0.75 g) while maintaining the reaction at 0-10° C. The reaction was stirred at this temperature for an additional hour before allowing the mixture to stand at room temperature overnight. Tlc analysis (40% THF/hexane) at this point indicated that most of the succinimide ester had reacted. Water (40 ml) was added to the reaction flask and the contents stirred. The solution was then neutralised and extracted with ethyl acetate. The extract was washed with water, dried (sodium sulfate) and concentrated to dryness leaving the crude product as a yellow glass. Trituration with hexane yielded 6-[(aminophenylacetyl) amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid-z,z,z-octadeca-6,9,12-trienamide as a yellow powder.
