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: Levodopa and the DA D2 - like receptor agonist , LY - 171555 ( [ 4aR - trans ] - 4 , 4a , 5 , 6 , 7 , 8 , 8a , 9 - o - dihydro - 5n - propyl - 2H - pyrazo lo - 3 - 4 - quinoline hydrochloride ) were also used for comparison .
### Output Text:
<span class="chemical">Levodopa</span> and the <span class="chemical">DA</span> D2 - like receptor agonist , <span class="chemical">LY - 171555</span> ( <span class="chemical">[ 4aR - trans ] - 4 , 4a , 5 , 6 , 7 , 8 , 8a , 9 - o - dihydro - 5n - propyl - 2H - pyrazo lo - 3 - 4 - quinoline hydrochloride</span> ) were also used for comparison . 