The invention relates to a crystalline form of a triethylai salt of (2Z)-2-(2-amino-5-chlorothiazol-4-yl)-2-(3-N-tert- butoxycarbonylaminopropoxyimino)acetic acid. (I) The invention also relates to processes and intermediates for preparing the crystalline form. The crystalline form is useful as an intermediate for preparing cross-linked glycopeptide-cephalosporin antibiotics.