Cypenamine

Cypenamine, or phenylcyclopentamine, is a stimulant drug developed by a team at the William S. Merrill company in the 1940s. It is currently known only in scientific research and has never been developed for market use. Cypenamine is currently legal throughout the entire world, and though its chemical structure has a vague similarity to certain controlled stimulants like fencamfamine (Glucoenergan, Reactivan), it is likely that it is too distant for it to be considered an illicit analogue under the United States (U.S.) Federal Analogue Act (FAA) of the Controlled Substances Act (CSA).

Stereochemistry

2-Phenylcyclopentan-1-amine is a compound with two stereocenters. Thus, the following two enantiomeric pairs may exist:

• (1RS,2SR)-trans-2-phenylcyclopentan-1-amine
• (1RS,2RS)-cis-2-phenylcyclopentan-1-amine

The racemate (±)-trans-2-phenylcyclopentan-1-amine [1:1 mixture of (1R,2S)-trans-2-phenylcyclopentan-1-amine (box, left) and (1S,2R)-trans-2-phenylcyclopentan-1-amine (box, right)] is the active ingredient of cypenamine. Furthermore, the kinetic resolution of (±)-trans-2-phenylcyclopentan-1-amine by lipase B from Candida antarctica may effectivily performed by an aminolysis reaction.

Racemic cis-2-phenylcyclopentan-1-amine [1:1 mixture of (1R,2R)-cis-2-phenylcyclopentan-1-amine and (1S,2S)-cis-2-phenylcyclopentan-1-amine] has found no pharmacological application.

Homology

Cypenamine is a homolog of tranylcypromine, containing an expanded alicyclic ring that is two methylene units larger than the highly strained/reactive cyclopropane. The cyclohexane homologue has been reported, although the LD₅₀s were all less than for plain amphetamine, it was still a functional stimulant.

Synthesis

Clinical success with the monoamine oxidase inhibitor and amphetamine analogue tranylcypromine led to an exploration of the effect of ring size on activity.

Convenient syntheses makes use of the finding that hydroxylamine-O-sulfonic acid is soluble in diglyme and therefore is suitable for conversion of organoboranes from hindered and unhindered olefins into the corresponding amines, 1-Phenylcyclopentene is hydroborated in the usual way with borohydride and BF₃. Addition of H₂NOSO₃H followed by acid hydrolysis completes the synthesis of cypenamine with excellent regio and stereospecificity. I.e. anti-Markovnikov

See also

• Amphetamine
• Cyclopentamine
• Methamphetamine
• Propylhexedrine

References