52513-18-5 
 
(5R,6S)-7-Oxo-6-((R)-1-tributylsilanyloxy-ethyl)-3-trifluoromethanesulfonyloxy-4-thia-1-aza-bicyclo3.2.0hept-2-ene-2-carboxylicacidallylester 
 
(5R,6S)-3-(1,1-Dioxo-tetrahydro-1λ6-thiophen-3-ylsulfanyl)-7-oxo-6-((R)-1-tributylsilanyloxy-ethyl)-4-thia-1-aza-bicyclo3.2.0hept-2-ene-2-carboxylicacidallylester 
[1]Phillips;O'Neill[TetrahedronLetters,1990,vol.31,#23,p.3291-3294]