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: Sirolimus and mycophenolate mofetil for calcineurin - free immunosuppression in renal transplant recipients .
### Output Text:
<span class="chemical">Sirolimus</span> and <span class="chemical">mycophenolate mofetil</span> for calcineurin - free immunosuppression in renal transplant recipients . 