Synthetic studies on β-lactam antibiotics. Part 10. Synthesis of 7β-[2-carboxy-2-(4-hydroxyphenyl)acetamido]-7.alpha.-methoxy-3-[[(1-methyl-1H-tetrazol-5-yl)thio]methyl]-1-oxa-1-dethia-3-cephem-4-carboxylic acid disodium salt (6059-S) and its related 1-oxacephems