Preferred IUPAC name of Protoporphyrin IX

I was looking up protoporphyrin IX and was surprised to find that no two websites gave the same IUPAC name for the compound. Here are some examples:


1. 3,3'-(7,12-Diethenyl-3,8,13,17-tetramethylporphyrin-2,18-diyl)dipropanoic acid (**EPA**)
2. 3,3'-(3,7,12,17-Tetramethyl-8,13-divinyl-2,18-porphyrindiyl)dipropanoic acid 
(**CHEMSPIDER**)
3. 3-[18-(2-carboxyethyl)-8,13-bis(ethenyl)-3,7,12,17-tetramethyl-22,23-dihydroporphyrin-2-yl]propanoic acid (**PUBCHEM**)


Anyone know if an IUPAC name is agreed upon among scientists or if there is a preferred IUPAC name?




I think both *EPA* and *ChemSpider* names are acceptable. However, I don't agree with dihydroporphyrin part in *PubChem* name. This is because the *Gold Book* gives following framework for porphyrin nucleus:


[![Protoporphyrin IX](https://i.stack.imgur.com/hsS2V.jpg)](https://i.stack.imgur.com/hsS2V.jpg)


According to the numbering the IUPAC name of protoporphyrin IX is 3,3'-(7,12-Diethenyl-3,8,13,17-tetramethylporphyrin-2,18-diyl)dipropanoic acid. This name based on least locant numbers for ethynyl group, which have higher priority before methyl groups (3,3'- is based on positions of propanoic acid). The same name is given to protoporphyrin IX in Ref.2, without 3,3'- locants.


**References:**


1. *IUPAC. Compendium of Chemical Terminology*, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. <https://doi.org/10.1351/goldbook>.
2. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN): Nomenclature of tetrapyrroles (Recommendations 1986); Prepared for publication by Gerard P. Moss, Queen Mary College, London, *Eur. J. Biochem.* **1988**, *178(2)*, 277-328 (<https://doi.org/10.1111/j.1432-1033.1988.tb14453.x>) ([PDF](https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1988.tb14453.x)).


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