Determination of the configuration of some penicillin S-oxides by 13C nuclear magnetic resonance spectroscopy

Abstract

The ¹³C n.m.r. spectra of a range of penicillins and some sulphoxides and sulphones derived from them are presented. Along the series sulphide, β-sulphoxide, α-sulphone there is a clear pattern in the changes of the shifts of C-2, -3, -5, and -6 and the C-2 methyl groups. This means that ¹³C n.m.r. spectroscopy can be used to determine the configuration of sulphoxides, and using this technique we have shown that oxidation of 6,6-dibromopenicillanic acid by peroxy-acid gives mainly the α-sulphoxide, whereas methyl penicillanate and its 6α-chloro- and 6α-bromo-derivatives give mainly the β-sulphoxides.