Novel bicyclic compounds

A compound of the general formula (I):

• 23
• or a salt thereof, wherein
• R1 represents a hydrogen atom, a hydroxyl group or a halogen atom;
• R2 represents NHSO2R3 or SO2NR4R4′;
• R3 represents an alkyl group containing from 1 to 6 carbon atoms or NR4R4′;
• R4 and R4′ may be the same or different and each independently represents a hydrogen atom or an alkyl group containing from 1 to 6 carbon atoms;
• R5 and R6 may be the same or different and each independently represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms or a phenyl group;
• X represents NH, a sulfur atom, an oxygen atom or a methylene group;
• Y represents an oxygen atom, NR7, a sulfur atom, a methylene group or a bond;
• R7 represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, or an acyl group containing from 1 to 6 carbon atoms;
• and
• * represents an asymmetric carbon atom.

A compound of the general formula (II):

• 24
• or a salt thereof, wherein
• W represents a hydrogen atom or an amino-protecting group;
• R5 and R6 may be the same or different and each independently represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, an optionally substituted phenyl group or an optionally substituted benzyl group, provided that R5 and R6 do not represent a hydrogen atom at the same time;
• X represents NH, a sulfur atom, an oxygen atom or a methylene group;
• Y represents an oxygen atom, NR7, a sulfur atom, a methylene group or a bond;
• and
• R7 represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, or an acyl group containing from 1 to 6 carbon atoms.

A compound of the general formula (II):

• 25
• or a salt thereof, wherein
• W represents a hydrogen atom or an amino-protecting group;
• R5 and R6 may be the same or different and each independently represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, an optionally substituted phenyl group or an optionally substituted benzyl group, provided that R5 and R6 do not represent a hydrogen atom at the same time;
• X represents NH, a sulfur atom, an oxygen atom or a methylene group;
• Y represents an oxygen atom, NR7 or a sulfur atom;
• and
• R7 represents a hydrogen atom, an alkyl group containing from 1 to 6 carbon atoms, or an acyl group containing from 1 to 6 carbon atoms.