*The following content is generated by AI and is for reference only.
<h3>Overview</h3>
<p>(E/Z)-FK-506 26,28-Allylic Ester Rearrangement Impurity is a critical process-related impurity generated during the synthesis of Tacrolimus. It arises from <strong>allylic rearrangement</strong> at the C26/C28 positions. Molecular formula: C<sub>44</sub>H<sub>73</sub>NO<sub>10</sub>; CAS: Not publicly assigned.</p>
<h3>Application</h3>
<ul>
<li><strong>Pharmaceutical R&D:</strong> Used as reference standard for method validation in tacrolimus production.</li>
<li><strong>Quality Control:</strong> Essential for HPLC/GC analysis to ensure drug purity compliance.</li>
<li><strong>Regulatory Submissions:</strong> Supports ICH Q3A/B guidelines for impurity characterization.</li>
</ul>
<h3>Precautions</h3>
<p>Strictly store under inert atmosphere at -20°C. Handle with PPE to avoid dermal exposure. Do not use in clinical formulations; solely for analytical research.</p>