FIELD: organic chemistry, antibiotics, pharmacy. SUBSTANCE: invention relates to novel derivatives of cephalosporin of the general formula (I) 
where R1 means hydrogen atom or ester group; R2 means the group of formulas (IIa) 
, (IIb) 
, (IIc) 
; Y means hydrogen atom, substituted alkyl or acyl; R4 means hydrogen atom, phenyl, cycloalkyl or alkyl; R5 means hydrogen atom, phenyl, cycloalkyl, lower alkyl, saturated or unsaturated 5-6-membered heterocyclyl optionally substituted with alkyl, trifluoroalkyl, oxo- or amino-group, benzothiazolyl or the group of formulas (IId) 
, (IIe) 
, (IIf) 
; R7 means alkyl; R8 means hydrogen atom, cycloalkyl or alkyl; R9 means hydrogen atom or alkyl; R10 means hydrogen atom, alkyl, substituted alkyl where a substituent is taken among trifluoroalkyl, pyridyl, hydroxy-, alkoxy-group, halogen atom, amino-group or residue of sulfonic acid; hydroxy-, amino-group, phenyl, alkenyl, cycloalkyl or the group of the formula N= CH-Phe where Phe means phenyl substituted with hydroxy-group; or R9 and R10 in common with nitrogen atom mean saturated, unsaturated or substituted 5-6-membered heterocyclyl comprising one or two nitrogen or oxygen atoms being a substituent is taken among formyl or alkyl and so on. The compound of the formula (IVa) 
where Rx means the group of the formula NH- C(CH3)3 and so on; Ry means NH and Rz means hydrogen atom and so on. Invention relates to also to a pharmaceutical composition designated for treatment of diseases caused by microorganisms and comprising the compound of the formula (I) in the form of pharmaceutically acceptable salt or as a free form in combination with at least one pharmaceutical carrier or diluting agent. Invention relates to also a method of treatment of diseases caused by microorganisms that involves administration of effective compounds of the formula (I) in a person who needs with so treatment. EFFECT: new antibacterial cephalosporins indicated above, valuable medicinal properties. 13 cl, 4 tbl
