Cephalosporins

1. A compound of formula

wherein

W is CH or N,

R 1 is hydroxy, (C 1-6 )alkoxy, halo(C 1-6 )alkoxy, hydroxycarbonyl(C 1-6 )alkoxy or (C 1-6 )alkoxycarbonyl(C 1-6 )alkoxy,

R 2 is hydrogen or an ester moiety,

R 3 is hydrogen, (C 1-6 )alkyl, (C 2-6 )alkenyl or (C 3-8 )cycloalkyl,

R 4 is hydrogen or (C 1-6 )alkyl,

is cyclohexyl or phenyl,

R 5 and R 6 independently of each other are hydrogen; (C 1-6 )alkyl; (C 2-6 )alkenyl; (C 6-18 )arylcarbonyl; (C 1-6 )alkylcarbonyl; (C 6-18 )aryloxy(C 1-4 )alkylcarbonyl; (C 1-6 ) alkylcarbonyl -(C 6-18 )arylcarbonyl; heterocyclyl(C 1-6 )alkylcarbonyl, wherein heterocyclyl comprises 5 or 6 ring members and 1 to 4 heteroatoms selected from N, O or S; (C 1-6 )alkylsulfonyl or (C 6-18 )arylsulfonyl,

X is NH, O, S or N—R 8 , wherein R 8 is (C 1-6 )alkyl or (C 3-8 )cycloalkyl,

Y is O or S, and

n and m independently of each other are 0 or 1.

2. The compound of claim 1 wherein

W is CH or N,

R 1 is hydroxy, methoxy, fluoromethoxy or (hydroxycarbonyl)(dimethyl)methoxy,

R 2 is hydrogen,

R 3 is hydrogen; (C 1-4 )alkyl, e.g. methyl or ethyl; allyl or cyclopropyl,

R 4 is hydrogen or (C 1-4 )alkyl, e.g. methyl,

is cyclohexyl, e.g. and the —(CH 2 ) m —NR 5 R 6 group is in the ortho, meta or para position,

R 5 and R 6 independently of each other are hydrogen; (C 1-3 )alkyl; allyl;

(C 1-4 )alkylcarbonyl; phenylcarbonyl, wherein phenyl is optionally substituted by (C 1-4 )alkylcarbonyloxy; phenyoxymethylcarbonyl; phenylsulfonyl, wherein phenyl is substituted by amino or (C 1-4 )alkylcarbonylamino, or heterocyclyl comprising 5 ring members and 1 heteroatom selected from N, O or S,

X is NH, NCH 3 , NCH(CH 3 ) 2 , O, S or (C 3-8 )cycloalkyl substituted by amino,

n is 0, m is 0,

Y is S and

R 8 is C 1-4 )alkyl.

3. The compound of claim 1 wherein in formula IA

W is N or CH,

R 1 is hydroxy or fluoromethoxy,

R 2 , R 4 , R 5 and R 6 are hydrogen,

R 3 is C 1-4 )alkyl,

is cyclohexyl,

X is NH,

n is 1 and m is 1.

4. The compound of claim 1 wherein in formula IA

W is N,

R 1 is fluoromethoxy,

R 2 , R 4 , R 5 and R 6 are hydrogen,

R 3 is C 1-4 )alkyl,

is phenyl,

X is NH,

n is 1 and m is 0.

5. The compound of claim 1 wherein in formula IA

W is CH or N,

R 1 is hydroxy or fluoromethoxy,

R 2 , R 4 , R 5 and R 6 are hydrogen,

R 3 is C 1-4 )alkyl,

is phenyl,

X is NH,

n is 1 and m is 1.

6. A compound of formula

7. A compound in the form of a salt,said compound being a compound of formula

or of formula

wherein

W is CH or N,

R 1 is hydroxy, (C 1-6 )alkoxy, halo(C 1-6 )alkoxy. hydroxycarbony(C 1-6 )alkoxy or (C 1-6 )alkoxycarbonyl(C 1-6 )alkoxy,

R 2 is hydrogen or an ester moiety,

R 3 is hydrogen, (C 1-6 )alkyl, (C 2-6 )alkenyl or (C 3-8 )cycloalkyl,

R 4 is hydrogen or (C 1-6 )alkyl,

is cyclohexyl or phenyl,

R 5 and R 6 independently of each other are hydrogen; (C 1-6 )alkyl; (C 2-6)alkenyl;

(C 6-18 )arylcarbonyl; (C 1-6 )alkylcarbonyl; (C 6-18 )aryloxyl(C 1-4 )alkylcarbonyl; (C 1-6 alkylcarbonyl- (C 6-18 )arylcarbonyl; heterocyclyl(C 1-6 )alkylcarbonyl, wherein heterocyclyl comprises 5 or 6 ring members and 1 to 4 heteroatoms selected from N, O or S; (C 1-6 )alkylsulfonyl or (C 6-18 )arylsulfonyl,

X is NH, O, S or N-R 8 , wherein R 8 is (C 1-6 )alkyl or (C 3-8 )cycloalkyl,

Y is O or S, and

n and m independently of each other are 0 or 1.

8. A pharmaceutical composition comprising a compound according to claim 1 in association with at least one pharmaceutical excipient.

9. A method of treatment of microbial diseases which comprises administering to a subject in need of such treatment an effective amount of a compound according to claim 1 .

10. A process for preparing a compound of formula IA

or a compound of formula IB

said process comprising reacting a compound of formula III

with a compound of formula IVA

or a compound of formula IVB

wherein

W is CH or N,

R 1 is hydroxy, (C 1-6 )alkoxy, halo(C 1-6 )alkoxy, hydroxycarbonyl(C 1-6 )alkoxy or (C 1-6 )alkoxycarbonyl(C 1-6 )alkoxy,

R 2 is hydrogen or an ester moiety,

R 3 is hydrogen, (C 1-6 )alkyl, (C 2-6 )alkenyl or (C 3-8 )cycloalkyl,

R 4 is hydrogen or (C 1-6 )alkyl,

is cyclohexyl or phenyl,

R 5 and R 6 independently if each other are hydrogen; (C 1-6 )alkyl; (C 2-6 )alkenyl; (C 6-18 )arylcarbonyl; (C 1-6 )alkylcarbonyl; (C 6-18 )aryloxy(C 1-4 )alkylcarbonyl; (C 1-6 )alkylcarbonyl-

(C 6-18 )arylcarbonyl; heterocyclyl(C 1-6 )alkylcarbonyl; wherein heterocyclyl comprises 5 or 6 ring members and 1 to 4 heteroatoms selected from N, O or S; (C 1-6 )alkylsulfonyl or

(C 6-18 )arylsulfonyl,

X is NH, O, S or N-R 8 , wherein R 8 is (C 1-6 )alkyl or (C 3-8 )cycloalkyl,

Y is O or S,and n and m independently of each other are 0 or 1 .