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: Dexrazoxane protects against myelosuppression from the DNA cleavage - enhancing drugs etoposide and daunorubicin but not doxorubicin .
### Output Text:
<span class="chemical">Dexrazoxane</span> protects against myelosuppression from the DNA cleavage - enhancing drugs <span class="chemical">etoposide</span> and <span class="chemical">daunorubicin</span> but not <span class="chemical">doxorubicin</span> . 