Adatanserin

1 Identity

Non-peptide small molecule - adamantane-1-carboxamide with a 1-(2-pyrimidinyl)piperazine head group (azapirone family architecture)

Sequence

No defined sequence - this is a non-peptide small molecule and no peptide sequence exists for it. N-[2-(4-pyrimidin-2-ylpiperazin-1-yl)ethyl]adamantane-1-carboxamide: an adamantane-1-carboxamide joined through a two-carbon ethylene linker to the N4 nitrogen of a 1-(2-pyrimidinyl)piperazine. Achiral - the adamantane bridgehead is not a stereocenter and a 1,4-disubstituted piperazine introduces none - so the molecule cannot have an enantiomeric impurity and a chiral method must not be added to it by reflex.

Molecular formula

C21H31N5O (free base); C21H32ClN5O (hydrochloride).

Average mass

369.513 Da (C21H31N5O, free base); 405.971 Da (C21H32ClN5O, hydrochloride). Listings commonly print the rounded 369.51 and 405.97.

Monoisotopic mass

369.25286 Da free base; 405.22954 Da hydrochloride. Listings commonly print the rounded 369.2529 and 405.2295. [M+H]+ 370.2601 for the free base. PubChem reports the exact and monoisotopic mass as 369.25286063 for the free base, which agrees to five decimal places.

Salt / variant note

(1) the salt form against itself is the first confusable and it is A 9.9% gravimetric error. Free base C21H31N5O at 369.51 against hydrochloride C21H32ClN5O at 405.97: the same number of molecules, 9.9% different in weight. NCATS registers the hydrochloride as its own substance and the catalog listings in this channel do not state which form would be supplied, so a gravimetric assay run against the wrong assumed form is 9.9% wrong before anything else goes wrong. (2) the isomer no mass spectrometer separates, and it is an approved drug. Adatanserin plus one oxygen is C21H31N5O2, 385.51 average / 385.2478 monoisotopic - and that is the exact molecular formula of buspirone, a cheap, universally available approved product built on the identical 1-(2-pyrimidinyl)piperazine head group. A mono-oxygenated adatanserin process impurity and buspirone are formally isomeric. No instrument at any resolution separates them by mass; only retention time against a characterized standard, MS/MS fragmentation or NMR does. Buspirone hydrochloride is C21H32ClN5O2, 421.97 / 421.2245. (3) The rest of the azapirone family shares that head group and clusters within about 45 Da of the parent - every one a candidate substitution, and every one resolvable only by retention time and fragmentation, not by nominal mass. (4) The two obvious process residues from the obvious synthetic route, both of which belong on an honest related-substances table: 1-(2-pyrimidinyl)piperazine, C8H12N4, 164.21 / 164.1062, and adamantane-1-carboxylic acid, C11H16O2, 180.25 / 180.1150. Note the arithmetic: 164.21 plus 180.25 minus water is 326.44, not 369.51, so a certificate reporting only fragment masses has characterized the pieces and not the product. (5) On the adamantane side the cheap substitutions are amantadine, C10H17N, 151.25 / 151.1361, and memantine, C12H21N, 179.31 / 179.1674 - both far lighter, both trivially available, both caught by a single accurate mass and by nothing a certificate omitting one would carry.

2 Class & testing panel

Form

Single article

Testing panel

P6 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

A small sponsor literature from the early 1990s: receptor-binding characterization in vitro, rodent behavioral pharmacology, and limited early-phase human data. No primary publication has appeared in roughly two decades and no reference standard is commercially cataloged. What does not exist: any controlled human trial reported to completion, any current-decade physicochemical or pharmacological characterization, and any independent replication of the binding data. The compound is described in the originating sponsor's in-vitro literature as a combined 5-HT1A and 5-HT2A receptor ligand; that is a binding property measured in a preparation and is recorded here as identity context, not as an effect. The citation index page states that this compound's literature is closed rather than emerging.

4 Storage & specification

Storage

Supplied as the crystalline hydrochloride salt in an amber glass bottle with a desiccant sachet and a tamper-evident closure. Labeled: store at 2-8 degrees C, protect from light, keep desiccated. A small molecule of this class is not genuinely cold-chain dependent; 2-8 degrees C is a conservative condition held pending the company's own data, and the label is revised down to controlled room temperature, 15-25 degrees C, if and only if that data supports it.

Shelf life

Provisional 24 months at 2-8 degrees C for a crystalline hydrochloride of this class, set on the company's own stability data and revised as that data accrues. Each lot is dated from its date of manufacture and carries that retest date on its certificate.