The cephalosporin derivatives cephradine, cephalexin, cefaclor, and cefadro
xil form complexes with beta-naphthol, provided water is present. The cryst
al structures of these complexes have been determined by single-crystal X-r
ay diffraction, The complexes appear to be inclusion compounds of the clath
rate type. In all cases, the cephalosporin molecules play the role of host,
while beta-naphthol is the guest molecule. Water molecules, which are acco
mmodated in the crystal, play an essential role in the interaction between
the guest and host molecules. Cephradine, cephalexin, and cefaclor form iso
morphous complexes with beta-naphthol, whereas cefadroxil crystallizes in a
different morphology. The crystal structures are described in detail and d
iscussed in terms of hydrogen-bonding, van der Waals and electrostatic inte
ractions. The structure of the cefadroxil complex is basically different fr
om that of the other three complexes, although there are notable structural
similarities.