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: OBJECTIVE : To report a case of syndrome of inappropriate anti - diuretic hormone ( SIADH ) secretion associated with desvenlafaxine .
### Output Text:
OBJECTIVE : To report a case of syndrome of inappropriate anti - diuretic hormone ( SIADH ) secretion associated with <span class="chemical">desvenlafaxine</span> . 