Structural study of fosfomycin [(-)-cis-1,2-epoxypropylphosphonic acid] salts and related compounds

Disodium, calcium, and ( + )-a-phenethylammonium salts of fosfomycin, the sodium salt of the monomethyl ester, and the dimethyl ester of fosfomycin have been studied by 1H, 13C, and 31P n.m.r., Lr., and Raman spectroscopy. From the n.m.r. study it can be deduced that the steric factors are mainly responsible for the molecular arrangement of these compounds in solution. Taking into account the rigidity of the oxiran ring, the n.m.r. results have been correlated with X-ray data for the (+)-α- phenethylammonium salt of fosfomycin and sodium methyl (-)-cis-1,2- epoxypropylphosphonate. l.r. and Raman data confirm the known structure of fosfomycin derivatives deduced from the routes for their synthesis. Moreover these data suggest the existence of rotational isomerism in the dimethyl ester of fosfomycin.We thank Bruker Spectrospin A6, Zurich-Fallanden, for recording some 'H n.m.r. spectra at 250 MHz and 31P n.m.r. spectra at 101 MHz, Dr. Rico, lnstituto de Estructura de la Materia, C.S.I.C., Madrid, for recording the 13C n.m.r. spectra at 22.6 MHz and for valuable criticisms, and Dr. J. V. García-Ramos, Instituto de Optica, C.S.I.C., Madrid, for recording some Raman spectra.Peer Reviewe