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: BACKGROUND : Pemoline is an oxazolidine derivative that is structurally different from amphetamines and used in the treatment of attention deficit disorder .
### Output Text:
BACKGROUND : <span class="chemical">Pemoline</span> is an <span class="chemical">oxazolidine</span> derivative that is structurally different from <span class="chemical">amphetamines</span> and used in the treatment of attention deficit disorder . 