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: The compound GYKI - 41 099 , as a beta - adrenergic antagonist , is 3 - 8 times more potent than propranolol in vitro and in vivo .
### Output Text:
The compound <span class="chemical">GYKI - 41 099</span> , as a beta - adrenergic antagonist , is 3 - 8 times more potent than <span class="chemical">propranolol</span> in vitro and in vivo . 