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: Transient platypnea - orthodeoxia - like syndrome induced by propafenone overdose in a young woman with Ebstein ' s anomaly .
### Output Text:
Transient platypnea - orthodeoxia - like syndrome induced by <span class="chemical">propafenone</span> overdose in a young woman with Ebstein ' s anomaly . 