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: Case report : Dexatrim ( Phenylpropanolamine ) as a cause of myocardial infarction .
### Output Text:
Case report : <span class="chemical">Dexatrim</span> ( <span class="chemical">Phenylpropanolamine</span> ) as a cause of myocardial infarction . 