In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: We report the case of a patient who developed acute hepatitis with extensive hepatocellular necrosis , 7 months after the onset of administration of clotiazepam , a thienodiazepine derivative .
### Output Text:
We report the case of a patient who developed acute hepatitis with extensive hepatocellular necrosis , 7 months after the onset of administration of <span class="chemical">clotiazepam</span> , a <span class="chemical">thienodiazepine</span> derivative . 