Abstract
The preparation of unique penicillin derivatives containing an exocyclic allene at the 6 position (6-vinylidenepenams) is described. The synthetic scheme utilizes 6-oxopenicillinates as intermediates which stereospecifically add acetylide anions forming propargylic alcohols. Displacement of the corresponding propargylic triflates with higher order cuprate reagents and with copper(I) halides proceeds rapidly and stereospecifically. Halogen-metal exchange of the 6-(halovinylidene) -penams is described. The derived allenyl anions can be trapped by electrophiles. Conversion of selected allyl and benzhydryl esters to the corresponding carboxylic acids is described. The β-lactamase inhibitory activity of the 6-(tert-butylvinylidene)penam sulfone is documented
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