Posted by naturalproductman on March 17, 2014
Someone has brought to my attention the isolation of a recent alkaloid containing a strange alkynol attached to a nitrogen.
The main supporting evidence for this structure is the 3-bond HMBC correlation of the OH proton to the alkyne carbon taken in DMSO (the alcohol is at ~9.8 ppm). The fishy thing here is that there is no 2-bond HMBC correlation (I assume it would be two bond from O-H and C-O) from the OH to the nearest alkyne carbon.
An interesting question would be how this alkynol would be introduced in the biological system. Alkynes are usually precursors to alkynols in P450 reactions and give rise to a rearrangement to form ketenes, which inactivate the enzymes.
Synthetically, I first saw alkynol structures from Sergey Kozmin’s work back in 2006. I should say that even here they are not alkynols – they are siloxy alkynes.
Perhaps anybody else has an opinion on this interesting structure?