PCT No. PCT/US97/22356 Sec. 371 Date Mar. 29, 1999 Sec. 102(e) Date Mar. 29, 1999 PCT Filed Dec. 5, 1997 PCT Pub. No. WO98/25932 PCT Pub. Date Jun. 18, 1998Described are antibacterial agents of formula (I): X is O, S or N-R8; R1, R2, R3 and R8 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, NR2, NR'COR', CN, CO2R' or CONR2', halogen, CN, CO2R, COR, CON(R)2, CON(R'')2, SR, SON, SCO2R or SCON(R)2; R4 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, NR2, NR'COR', CN, CO2R' or CONR2', halogen, CN, NO2, N(R)2, NRCOR, NRCOR'', COR, CO2R, CON(R)2, CON(R'')2, NRCON(R)2, NRCO2R; R5 is 1-6 straight or branched alkyl, a cycloalkyl of 3-6 carbons, 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, NR2, NR'COR', CN, CO2R' or CONR2', halogen, OR, N(R)2, NRCOR, NRCOR'', COR, CON(R)2, CON(R'')2, SR or SO2R; R6, R7 are independently H, straight or branched alkyl of 1-6 carbons, cycloalkyl of 3-6 carbons, COR, COR'', SO2NR2, CONR2 and these may be optionally substituted by any of the groups listed for R5; R is H, straight or branched alkyl of 1-6 carbon atoms, cycloalkyl of from 3-6 carbon atoms, heterocyclic ring of from 5-8 atoms with 1-3 heteroatoms as nitrogen, oxygen or sulfur, or pheny, all of which may be optionally substituted by halogen, OR', NR'2, NR'COR', CN, CO2R', CONR'2, R' is H, alkyl of from 1-3 carbon atoms or Ph; R'' is part of a naturally occurring amino acid connected via an amide or acyl bond as determined by the formula; halogen is any one of fluoro, chloro, bromo or iodo; or a pharmaceutically acceptable salt.