| abstract |
A compound of the formula: n<CHEM>n in which R<1> is hydrogen, halogen, amino, acylamino, isocyano or protected hydroxy(lower)alkyl,n R<2> is hydrogen or an organic group optionally substituted by suitable substituent(s), andn R<3> is carboxy or a protected carboxy group, or a salt thereof. n<??>The invention also relates to processes for their preparation, and their use for preparing antibiotics. |