title: Synthesis and in vitro evaluation of new benzovesamicol analogues as potential imaging probes for the vesicular acetylcholine transporter.
abstract: Our goal was to synthesize new stereospecific benzovesamicol analogues, which could potentially be used as SPECT or PET radioligands for the vesicular acetylcholine transporter (VAChT). This paper describes the chemical synthesis, resolution and determination of binding affinity for four enantiomeric pairs of derivatives. Their intrinsic affinities were determined by competition against binding of [3H]vesamicol to human VAChT. Of the eight enantiomers, (E)-(R,R)-5-AOIBV [(R,R)-3], and (R,R)-5-FPOBV [(R,R)-4] displayed the highest binding affinities for VAChT (Kd=0.45 and 0.77 nM, respectively), which indicated that an elongation of the chain from 5-idodo as in the case of 5-iodobenzovesamicol (5-IBVM), to a 5-(E)-3-iodoallyloxy or 5-fluoropropoxy substituent, as in 5-AOIBV and 5-FPOBV, respectively, was very well tolerated at the vesamicol binding site. The enantiomer (R,R)-4-MAIBV [(R,R)-16], which retains the basic structure of (-)-5-IBVM but possess an additional aminomethyl substituent in the 4-position of the piperidine ring, displayed lower binding affinity (Kd=8.8 nM). Nevertheless, the result suggests that substitution at this position may be an interesting alternative to investigate for development of new benzovesamicol analogues. As expected, the corresponding (S,S) enantiomers displayed lower Kd values, they were approximately 10-fold lower in the case of (S,S)-5-FPOBV (Kd=8.4 nM) and (E)-(S,S)-5-AOIBV (Kd=4.3 nM). (R,R)-3, and (R,R)-4 showed the same high affinity for VAChT as (-)-5-IBVM and may be suitable as imaging agents of cholinergic nerve terminals.
authors.affiliation: Faculté de Pharmacie, INSERM U619, Laboratoire de Biophysique Médicale, 31 Av. Monge, 37200 Tours, France.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Zea-Ponce
authors.forename: Sylvie
authors.initials: S
authors.lastname: Mavel
authors.forename: Thaer
authors.initials: T
authors.lastname: Assaad
authors.forename: Shane E
authors.initials: SE
authors.lastname: Kruse
authors.forename: Stanley M
authors.initials: SM
authors.lastname: Parsons
authors.forename: Patrick
authors.initials: P
authors.lastname: Emond
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chalon
authors.forename: Nicolas
authors.initials: N
authors.lastname: Giboureau
authors.forename: Michael
authors.initials: M
authors.lastname: Kassiou
authors.forename: Denis
authors.initials: D
authors.lastname: Guilloteau
mesh_terms: D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D026901:Membrane Transport Proteins / Q000737:chemistry*; D015335:Molecular Probes; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism; D050494:Vesicular Acetylcholine Transport Proteins
chemical_list: D026901:Membrane Transport Proteins; D015335:Molecular Probes; D010880:Piperidines; D050494:Vesicular Acetylcholine Transport Proteins; C502757:benzovesamicol