Abstract: Described are antibacterial agents of formula (I): X is O, S or N--R.sub.8 ; R.sub.1, R.sub.2, R.sub.3 and R.sub.8 are independently H, straight or branched alkyl of 1-6 carbons, cycloalkyl of 3-6 carbons, alkenyl or alkynyl of from 2 to 6 atoms, R heterocyclic ring of from 5-8 atoms with 1-3 heteroatoms as nitrogen, oxygen or sulfur, or phenyl, all of which rings may be optionally substituted up to 3 times by halogen, OR, NR.sub.2, NR'COR', CN, CO.sub.2 R' or CONR.sub.2 ', halogen, CN, CO.sub.2 R, COR, CON(R).sub.2, CON(R").sub.2, SR, SON, SCO.sub.2 R or SCON(R).sub.2 ; R.sub.4 is H, straight or branched alkyl of from 1-6 carbon atoms, alkenyl or alkynyl of from 2 to 6 atoms, heterocyclic ring of from 5-8 atoms with 1-3 heteroatoms as nitrogen, oxygen or sulfur or phenyl, all of which rings may be optionally substituted up to 3 times by halogen, OR, NR.sub.2, NR'COR', CN, CO.sub.2 R' or CONR.sub.2 ', halogen, CN, NO.sub.2, N(R).sub.2, NRCOR, NRCOR", COR, CO.sub.2 R, CON(R).sub.2, CON(R").sub.2, NRCON(R).sub.