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: Discovery and scale - up syntheses of compound 1 are described in detail , highlighting optimization steps that increased the overall yield of 1 from 10 . 0 % to 30 . 5 % .
### Output Text:
Discovery and scale - up syntheses of compound 1 are described in detail , highlighting optimization steps that increased the overall yield of 1 from 10 . 0 % to 30 . 5 % . 