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: Conformationally restricted analogs of BD1008 and an antisense oligodeoxynucleotide targeting sigma1 receptors produce anti - cocaine effects in mice .
### Output Text:
Conformationally restricted analogs of <span class="chemical">BD1008</span> and an antisense <span class="chemical">oligodeoxynucleotide</span> targeting sigma1 receptors produce anti - <span class="chemical">cocaine</span> effects in mice . 