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: The results also show valsartan to be well tolerated and suggest that it is not associated with side effects characteristic of this comparator class , dihydropyridine calcium antagonists .
### Output Text:
The results also show <span class="chemical">valsartan</span> to be well tolerated and suggest that it is not associated with side effects characteristic of this comparator class , <span class="chemical">dihydropyridine</span> <span class="chemical">calcium</span> antagonists . 