Hydrazide Nitrosamine Formation

I have a hydrazide where R1, R2, and R3 are all carbonyls. So, there is a carbonyl immediately adjacent to each N. I cannot find any examples of similar molecules forming nitrosamines. Does anyone think this would be possible?


To my understanding nitrosation of such compounds seems to be unlikely due to the electron withdrawing properties of the amide/carbonyl oxygen. Even if formed, such compounds shouldn’t be considered as cohort of concern since they essentially lack alpha-hydrogens necessary for CYP450 mediated metabolism and subsequent formation of alkyldiazonium, a feature characteristic of high potent N-nitrosamine impurities.


@Muzaffar Nitroso mefenamic acid also does not have alpha-hydrogens. Still EMA has considered in Nitrosamine with AI of 78000 ng/day. Any thought on this case?

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N-Nitroso mefenamic acid, just like N-Nitroso-diphenylamine (TD50 167 mg/kg/day) is a diaryl N-nitrosamine lacking alpha-hydrogens. They are known to be mutagenic via a different mechanism i.e. trans-nitrosation potentially through Fischer−Hepp rearrangement. They are very weak carcinogens with AI much higher than 1.5 mcg/day and therefore non-cohort of concern compounds. For the diaryl N-nitrosamines you can consider an AI of 78000 ng/day in accordance with the EMA guidance.


Thanks for the responses @Muzaffar and @hgajjar

This is very much appreciated. I should have thought of the alpha hydrogens. This information greatly changes our scope of work.

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Very well analyzed, Muzaffar,
the nitrosamines are not always activated by alpha hydroxylation, there are several other routes.


If you have something like C=(O)NHNH-C=O group, this is not going to produce a nitrosamine anyway. Remember, we talked about nitrosamines vs nitrosamides. I think we need to contain ourselves to nitrosamine formation at this time. Also, four electron withdrawing bulky groups will make the formation of a N-nitroso compound quite challenging.


I see what you mean. Thank you. This is greatly appreciated.

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@ASrinivasan Recently we received query from Health Canada mentioning “intermediates and impurities contain amide functional group with α-hydrogen” and asked to provide the results of a robust risk assessment for the presence of nitrosamine impurities in the proposed drug product.

@Muzaffar provided an accurate analysis. Even if this species would get nitrosated (Which I doubt it would) it would not be a nitrosamine and would not be within the cohort-of-concern.