| 摘要 |
beta -Lactam antibiotics of formula (I) or a salt thereof wherein R<1> is hydrogen, methoxy or formamido; R<2> is an acyl group; CO2R<3> is a carboxy group or a carboxylate anion, or R<3> is a readily removable carboxy protecting group; L is -CH=, -(CH2)n where n is 0 or 1, -(CH2)x-Y-(CH2)y- where x and y are independently 0 or 1 and Y is sulphur or oxygen; R<4> is an optionally substituted gamma - or delta -thiolactone or lactam ring optionally containing one or (where applicable) two endocyclic double bonds; and X is S, SO, SO2, O or CH2, useful in the treatment of bacterial infections in humans and animals. |
