25I-NBOMe (2C-I-NBOMe, Cimbi-5, also shortened to "25I") is a psychedelic drug and derivative of the substituted phenethylamine psychedelic 2C-I. It was discovered in 2003 by chemist Ralf Heim at the Free University of Berlin, who published his findings in his PhD dissertation. The compound was subsequently investigated by a team at Purdue University led by David Nichols.
The carbon-11 labelled version of 25I-NBOMe, [11C]Cimbi-5, was synthesized and validated as a radiotracer for positron emission tomography (PET) in Copenhagen. Being the first 5-HT2A receptor full agonist PET radioligand, [11C]-CIMBI-5 shows promise as a more functional marker of these receptors, particularly in their high affinity states.
Like other 2C-X-NBOMe molecules, 25I-NBOMe is a derivative of the 2C family of phenethylamines described by Alexander Shulgin in his book PiHKAL. Specifically, 25I-NBOMe is an N-benzyl derivative of the phenethylamine molecule 2C-I, formed by adding a 2-methoxybenzyl (BnOMe) onto the nitrogen (N) of the phenethylamine backbone. This substitution significantly increases the potency of the molecule.