摘要 |
<p>A process for the preparation of a compound of formula (IV) <CHEM> or an ester or a salt thereof comprising 1) reacting a compound of formula (I) <CHEM> (wherein Ra represents C1-4alkyl, Rb represents C1-4alkyl and Rc represents C1-6alkyl> with a compound of formula X2C=O (wherein each X independently represents a leaving group) to give a compound of formula (II) <CHEM> (wherein Ra, Rb and Rc are as hereinbefore defined); and 2) reacting said compound of formula (II) with a compound of formula (III) <CHEM> (wherein Rd represents hydrogen or a protecting group), compounds of formula (II), and a process for the preparation of compounds of formula (I).</p> |