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: Pharmacology of GYKI - 41 099 ( chlorpropanol , Tobanum ) a new potent beta - adrenergic antagonist .
### Output Text:
Pharmacology of <span class="chemical">GYKI - 41 099</span> ( <span class="chemical">chlorpropanol</span> , <span class="chemical">Tobanum</span> ) a new potent beta - adrenergic antagonist . 