Over the past three decades a large variety of antibiotics have become available for clinical use. Unfortunately, the wide-spread use of these antibiotics has caused a rapid increase in the number of bacterial strains that are resistant to the currently available antibiotics.
S. Hecker et al., PCT Application WO 01/21623 (published 29 Mar. 2001), describes 7-acylamino-3-heteroarylthio-3-cephem carboxylic acid antibiotics and prodrugs thereof. The compounds described therein are active as antibiotics against a wide spectrum of organisms including organisms which are resistant to beta-lactam antibiotics. However, the compounds described therein are complicated, and require the synthesis of a variety of separate groups. One group which must be synthesized to make these compounds is the C3 side-chain, an intermediate for which is illustrated on page 51 therein as follows: However, the synthesis of such C3 side chain groups as set forth in S. Hecker et al. requires in excess of 6 steps (see pages 49-52 therein). Accordingly, there is a need for new ways to make the intermediates used to make the antibiotic compounds described in S. Hecker et al.