All seemed very promising with the 'toluene method' today, with a molten clear product forming white crystals upon recrystallization from methanol. However, the melting point was low and wide: 145-152 C, suggesting it not be metformin hydrochloride: a value even below the starting materials. Interesting. Wonder what it could be?
Perhaps those 'metformin impurity C' type compounds might provide the (an) answer. Or, maybe metformin, the free base? A google search revealed the following links for further investigation:
The first link shows a number of melamine compounds.
Google searching some of the metformin related products in the first reference above via the CAS number reveals:
Metformin EP Impurity B (Monoguanyl Melamine), CAS No. 4405-08-7, C4H8N8 M.W. 168.16, M-423
http://www.carbosynth.com/carbosynth/website.nsf/(w-productdisplay)/D5ADF9334A7D2C68802579CF00631F27
CAS No. of metformin hydrochloride (1115-70-4) and metformin (free base) (657-24-9):
https://www.clearsynth.com/en/search.asp?category=API Standards&parentchemical=Metformin
