A compound of formula (I):
1
wherein
R
&agr;
is hydrogen, optionally substituted (C
1-6
)alkyl or optionally substituted aryl;
R
&bgr;
is hydrogen, optionally substituted (C
1-6
)alkyl or optionally substituted aryl; or
R
&agr;
and R
&bgr;
together form an optionally substituted 5 or 6 membered heterocyclic ring with or without additional heteroatoms;
R
1
is (C
1-6
)alkyl which is unsubstituted or substituted by fluoro, a hydroxy group which is optionally protected by a removable hydroxy protecting group, or by an amino group which is optionally protected by a removable amino protecting group;
R
2
is hydrogen or methyl; and
—CO
2
R
3
is carboxy or a carboxylate anion or the group R
3
is a removable carboxy protecting group. This invention also relates to processes for its preparation, intermediates and pharmaceutical compositions comprising compounds of formula (I). Compounds of formula (I) which include pharmaceutically acceptable salts or pharmaceutically acceptable in vivo hydrolysable esters thereof have a broad spectrum of anti-bacterial activity and show good stability towards DHP-1.
THE communication from Prof. Wilson Baker and his collaborator1 prompts us to intimate that we also have concerned ourselves with the sydnones, but from the point of view that their formation might be related to the racemization of ñ-acetylaminocarboxylic acids by acetic anhydride. Bergmann and Zervas2 adduced evidence that this change depended on enolization of the anhydro-compound to I.