(R)-3-Acetoxymethyl-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-Hydroxymethyl-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-Methoxycarbonyl-vinyl)-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-Cyano-vinyl)-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-Formyl-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-2-tert-Butoxycarbonyl-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-Carbamoyl-vinyl)-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-Methoxycarbonyl-vinyl)-4-methylene-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-Acetoxymethyl-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-Buta-1,3-dienyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-tert-Butoxycarbonyl-vinyl)-4-methylene-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((Z)-2-Chloro-2-methoxycarbonyl-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-Buta-1,3-dienyl)-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(R)-3-Acetoxymethyl-4-methylene-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(R)-3-((E)-2-tert-Butoxycarbonyl-vinyl)-5,5,8-trioxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-2-Carbamoyl-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-2-Methoxycarbonyl-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-2-Cyano-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester

(2R,6R)-3-((E)-2-Nitro-vinyl)-8-oxo-7-[1-pyridin-2-yl-meth-(Z)-ylidene]-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid benzhydryl ester