Syntheses based on 1,2-secopenicillins. Part 4. A new tricyclic beta-lactam derivative.

Abstract

Heating (3R,4R)-1-[azido-(t-butoxycarbonyl)methyl]-4-(prop-2-ynylthio)-3-(triphenylmethylamino)azetidin-2-one (4) in refluxing toluene resulted in smooth intramolecular cycloaddition of the azido-group to the acetylenic function to afford (5aR,6R,9ξ,)-t-butyl 6,7-dihydro-7-oxo-6-triphenylmethylamino-4H,5aH-azeto[2,1-b]-v-triazolo[3,4-e][1,3,5]thiadiazepine-9-carboxylate (5).