It has been a while since I posted last. My computer succumbed to some malware and although, it was a valiant fight, I declare that the malware was the victor. With a new system build, comes a new post; I feel oddly refreshed. Anyhow, I found this article in Organic Process Research & Development that was worthy of some conversation.
“Optimisation of Permanganate Oxidation and Suzuki Miyaura Coupling Steps in the Synthesis of a Na v 1.8 Sodium Channel Modulator” by M. Jonathan Fray et al, Organic Process Research & Development, 2010, 14 (1), pp 263–271.
As you know, sometimes, you are given a project, where the demand for material in the clinic is NOW. So you take the medicinal chemistry route and you make some changes to it, like optimize the steps, so you can deliver enough product. Occasionally, the route involves some things that are not ideal. I remember one particular incident, for instance, where I was using pivalic anhydride to protect an amino group in my molecule. After isolation, my material was still saturated with pivalic acid. I had even tried to purify my product by passing it through a chromatography column (It was a very big column, 5 kg silica gel in a walk-in hood). When I think of a potassium permangnate oxidation, I can only think of purple, lots of purple. I have had very few times where I had to perform a potassium permanganate oxidation. In this article, work was performed to optimize a potassium permanganate oxidation.
The author mentions that the material was to be made for clinical trials and that they ended up outsourcing the first part of the synthesis, the oxidation and the protection of the amino group. I haven’t ever seen a potassium permanganate oxidation done on large scale. Is this feasible ? I was curious what the Mn count was in the final product. Was there a need for a final polishing to remove manganese from the product. What is your experience ?