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: We conducted a double - blind , randomized phase II study to evaluate the safety and activity of combination therapy with N - butyl - deoxynojirimycin ( SC - 48334 ) ( an alpha - glucosidase I inhibitor ) and zidovudine versus zidovudine alone .
### Output Text:
We conducted a double - blind , randomized phase II study to evaluate the safety and activity of combination therapy with <span class="chemical">N - butyl - deoxynojirimycin</span> ( <span class="chemical">SC - 48334</span> ) ( an alpha - glucosidase I inhibitor ) and <span class="chemical">zidovudine</span> versus <span class="chemical">zidovudine</span> alone . 