The present invention provides a novel glycopeptide antibiotic derivative.These derivatives are represented by the formula (I)or a pharmaceutically acceptable salt or solvate thereof,whereinRA is -X1-Ar1-X2-Y-X3-Ar2whereinX1, X2 and X3 are single bond heteroatom-containing group selected from the group consisting of -N=, =N-, - NR1- (R1 is hydrogen or lower alkyl), -O-, -S-, -SO- and -SO2-, or a linkage thereof or alkylene or alkenylene optionally substituted and optionally interrupted by one or more of said heteroatom-containing groupY is -NR2CO-, -CONR2- (R2 is hydrogen or lower alkyl), or a group of the formula (II) wherein R3 is alkyleneAr1 and Ar2 are a carbocycle or a heterocycle which is optionally substituted and may have an unsaturated bondRB is -NHNRXRY or -NRZORWwhereinRX is hydrogen or lower alkylRY is hydrogen, optionally substituted lower alkyl, C(=NH)NH2, CSNH2, COCONH2, CN, optionally substituted heterocyclic group, and optionally substituted carbamoylRZ is hydrogen or lower alkylRW is hydrogen, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted heterocyclic group, optionally substituted heterocyclic carbonyl or optionally substituted carbamoylRC is hydrogen or optionally substituted alkyl, wherein said alkyl may be interrupted by a heteroatom-containing group selected from N=, =N-, -NR1- (R1 is hydrogen or lower alkyl), -O-, -S-, -SO- and -SO2- andR is optionally substituted alkyl.
