Morin Rearrangement

The acid‐promoted stereospecific transformation of penicillin sulfoxides into corresponding desacetoxycephalosporins is generally referred to as the Morin rearrangement. All the steps of this reaction have been presented. This reaction indicates the existence of a thermal equilibrium between the sulfoxide and the sulfenic acid. In addition, it offers the first direct chemical correlation between the penicillins and cephalosporins. This reaction is important for the preparation of antibiotics containing deacetoxy‐cephalosporin moiety.