By Donna M. Iula, Ph.D. - Vice President of Forensic Chemistry, Cayman Chemical

The basic fentanyl scaffold can be modified in four different regions leading to a myriad of new fentanyl varieties. Naming these substituted fentanyls has been inconsistent, causing confusion and leading to miscommunication in the forensic and toxicology communities. For example, any of the three compounds illustrated below could conceivably be named “2-methyl fentanyl.”

Cayman’s scientists standardized a fentanyl naming system to help provide a more unambiguous way to describe substituent placement on the fentanyl scaffold. This system differentiates the points of substitution by region in the following manner:

Common amide group swaps are typically named by placing the name of the moiety that is replacing the typical fentanyl ethyl group in front of the word ‘fentanyl.’ Examples include:

There are, however, some noteworthy legacy exceptions to this amide-group swap naming convention. When the typical phenethyl group was replaced by a different N-alkyl linker, those analogs were named similarly in the past. Benzyl fentanyl and furanylethyl fentanyl, for example, do not contain the phenethyl N-alkyl group off the piperidine nitrogen and those varieties were named by placing the name of the moiety replacing the phenethyl group in front of the word "fentanyl" as illustrated below.

Benzyl fentanyl(left) and furanylethyl fentanyl(right) are legacy exceptions to the current convention.

Given the existence of these legacy compounds and to prevent misunderstanding going forward, we name N-alkyl chain swaps by using the root word “norfentanyl,” which is understood to mean a fentanyl without substitution off the piperidine nitrogen.  For example, it would be less ambiguous to name the aforementioned benzyl fentanyl as “N-benzyl Norfentanyl.” The verbiage “N-benzyl” better describes where the benzyl group is located and clearly identifies that the benzyl moiety has replaced the typical fentanyl phenethyl group off the nitrogen.

Norfentanyl

Keep in mind that common fentanyl analog metabolites such as “Furanyl norfentanyl” do not have the “N“- designation and so it is clear that the furanyl norfentanyl represents a swap at the amide group and not an N-phenethyl swap.

Furanyl norfentanyl

If you are having trouble identifying or finding a compound of interest please contact our technical support department. Cayman can also provide assistance in the identification of unknown compounds and provides other tools on our Forensic Science Products page such as our Spectral Library, GC-MS Search Tool, and GC-MS Interpretation Guide to help chemists identify novel analogs.

To cite this naming system: Iula, D.M. Standardized Naming of Substituted Fentanyls. Article, Cayman Chemical (2018).