25CN-NBOH

25CN-NBOH (or NBOH-2C-CN) is a compound indirectly derived from the phenethylamine series of hallucinogens, which was discovered in 2011 by Martin Hansen at the University of Copenhagen. This compound is notable as one of the most selective agonist ligands for the 5-HT2A receptor yet discovered, with a pKi of 8.88 at the human 5-HT2A receptor and with 100x selectivity for 5-HT2A over 5-HT2C, and 46x selectivity for 5-HT2A over 5-HT2B. The tendency of the 4-cyano substitution to confer high 5-HT2A selectivity had previously been observed with DOCN, but this was not sufficiently potent to be widely adopted as a research ligand. 25CN-NBOH is still slightly less selective for 5-HT2A than the more complex cyclised derivative (2S,6S)-2-(2,5-dimethoxy-4-bromobenzyl)-6-(2-methoxyphenyl)piperidine, however it is also less complex to synthesise and has higher efficacy as a partial agonist of the 5-HT2A receptor.