Dear Writer, This is a Chemistry Literature Review Project, I would like you to write it carefully. The style of referencing is called: "Royal Society of chemistry". I will attach full details about it in a pdf file, please follow their style. My specialty in the university is "Drug discovery and development". This is the topic of my research: "Discovery of stable peptide-based Endomorphin-1 analogues as specific opioid receptor agonists for pain relief". It should contain an Introduction, Discussion, and conclusion. In the body of your writing, I would like you to create a comparison in a table between three or four studies about the drug "Endomorphin-1" to compare between them in terms of modifications which has been done for it. - Full hints are attached, please have a look carefully. - Your writing must be %100 free of plagiarism.