N-nitroso Torasemide Impurity formation and control

In our case, I confirm that it is very difficult discriminate a “fake” N-nitroso Torasemide standard (MW 377.46) from the hypotetical N-nitroso Torasemide (MW 377.42). We believe that the supplier made an honest mistake.
However the NMR confirmed that the structure does not correspond to the hypotetical N-nitroso Torasemide.
We will evaluate other suppliers, but we believe that no one obtained the correct substance.

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Did you use 1H-15N HSQC as 2D NMR?

dear ccdw,
first of all, happy new year :smiley:
regarding the ‘‘fake’’ N-nitrosoticagrelor, we did not performed any NMR studies in our edge. All the information came from our API manufacturers. In their technical assessments, several NMR technics have been applied.
Among them, 1H-15N HSQC and 1H-15N HMBC experiments were performed.
have a nice day

Thanks, I share the opinion that these are the go-to 2D NMR methods for these cases.
I had to use it a few times as well in such cases, but to my surprise initially not all NMR facilities had these type of measurements pretested to offer as services.

Best wishes.