ABSTRACT
N-(4-[(18)F]-Fluoropyridin-2-yl)-N-{2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl}-carboxamides were prepared by labeling their 4-nitropyridin-2-yl precursors through nitro substitution by the (18)F anion. In vitro and in vivo tests showed that the cyclohexanecarboxamide derivative is a reversible, selective and high affinity 5-HT1A receptor antagonist (IC50 = 0.29 nM, ki = 0.18 nM) with high brain uptake, slow brain clearance and stability to defluorination when compared with conventional standards. This PET radioligand is a promising candidate for an improved in vivo quantification of 5-HT1A receptors in neuropsychiatric disorders.
Subject(s)
Piperazines/chemistry , Positron-Emission Tomography/methods , Pyridines/chemistry , Receptor, Serotonin, 5-HT1A/metabolism , Animals , Binding, Competitive , Brain/diagnostic imaging , Brain/metabolism , Fluorine Radioisotopes , Male , Piperazines/metabolism , Piperazines/pharmacokinetics , Pyridines/metabolism , Pyridines/pharmacokinetics , Radioactive Tracers , Rats , Rats, Sprague-DawleyABSTRACT
Synthetic methodologies aiming at the creation of new phosphorus-centered functional groups are reported, as well as applications to the field of nucleotide chemistry. Thus, difluorophosphonothioate-based, ionic reagents 3b and 3d are shown to allow the stereocontrolled and efficient synthesis of phosphonodifluoromethyl analogues of nucleoside-3'-phosphates. An alternate, radical approach describes the use of hypophosphorous acid to stereoselectively link two furanosyl units in positions 3 and 5, and to provide an access to alpha,alpha-difluoro-H-phosphinates. These intermediates are shown to be precursors to the corresponding fluorinated phosphonic acids, phosphonothioic acids and variously substituted phosphinates.
Subject(s)
Nucleic Acids/chemistry , Nucleotides/chemistry , Organophosphates/chemistry , Nucleotides/chemical synthesis , Phosphinic Acids/chemistry , StereoisomerismABSTRACT
Efforts to develop synthetic methodologies allowing the preparation of alpha,alpha- difluorophosphonothioates, alpha,alpha-difluorophosphonodithioates, alpha,alpha-difluorophosphono- trithioates, and alpha,alpha-difluorophosphinates are reviewed in the light of applications in the field of modified oligonucleotides and cyclitol phosphates. Two successful approaches have been developed, based either on the addition of phosphorus-centered radicals onto gem-difluoroalkenes or on a process involving the addition of lithiodifluorophosphono- thioates 91 onto a ketone and the subsequent deoxygenation reaction of the adduct. The radical route successfully developed a practical route to alpha,alpha-difluoro-H-phosphinates which proved to be useful intermediates to a variety of phosphate isosters. The ionic route led to the first preparation of phosphonodifluoromethyl analogues of nucleoside- 3'-phosphates.
