Short communication Procedures for Preparation and Radiolabeling of a 3-Fluoropyrrolidine-Containing FDDNP Analog Andrej Fister,1 Jorge R. Barrio2 and Andrej Petric*'1'3 1 Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, SI-1000 Ljubljana, Slovenia 2 Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA 3 EN-FIST Centre of Excellence, Dunajska 156, 1000 Ljubljana, Slovenia * Corresponding author: E-mail: andrej.petric@fkkt.uni-lj.si Received: 07-05-2012 Dedicated to Professor Miha Tisler on the occasion of his 85th birthday Abstract A novel FDDNP analog, namely {1-[6-(3-fluoropyrrolidin-1-yl)-2-naphthyl]ethylidene}malononitrile, was synthesized to probe the influence of the applied structural changes at the donor-side of the molecule on tau protein aggregate binding. Reported is also a synthetic procedure, which can be directly applied to the preparation of the [18F]-radiolabeled compound. Keywords: FDDNP analogs, synthesis, molecular probes, tau-imaging 1. Introduction It has been demonstrated that FDDNP1 (1; (1-{6-[(2-fluoroethyl)(methyl)amino]naphthalen-2-yl}ethyli-dene)propanedinitrile) consistently labels all cross-P-sheet structures-containing protein aggregates found in neurodegenerative diseases.2 [18F]FDDNP is effective in in vivo imaging of tau fibrillar deposits in Alzheimer's disease2'3 that also have sufficient sensitivity to detect changes in regional tau pathology load in progressive su-pranuclear palsy (PSP) and produce differentiation from Parkinson's disease (PD) and frontotemporal dementia (FTD).4 In this work, by modifying the n-conjugation between the electron donor group (e.g., dialkylamino) with the electron acceptor (e.g., the 2-cyano acrylate unit) in the dialkylamino naphthalenyl-2-cyanoacrylate motif in FDDNP, we intent to produce tau-binding molecules with increased sensitivity and specificity for in vivo detection of tau aggregation in humans (e.g., vs. amyloid beta binding). This approach would offer a framework for fine-tuning the binding properties of new neurofibril-lary tau specific imaging probes in parallel with X-ray microcrystallography at atomic resolution in co-crystallization experiments.5 The ability of side chains in 1 to assume coplanar arrangement in respect to the naphthalene ring is a prerequisite for efficient interaction with P-sheet region of the aggregates. This has been demonstrated by the effect of structural differences in DDNP (2; {1-[6-(dimethylami-no)naphthalen-2-yl]ethylidene}propanedinitrile)6 and derivatives 3 and 4 (Figure 1) on binding characteristics. In Figure 1. Chemical structures of FDDNP (1), DDNP (2), and two conformationally restricted analogs (3 and 4) contrast to DDNP (2), the acceptor side-chain in 3 can neither rotate freely around the C-C bond because of large steric hindrance exhibited by the ieri-butyl group, nor can exist in a coplanar conformation, resulting in weak binding (Ki 520 nM). On the other hand, the acceptor side-chain in 4 is fixed to almost coplanar conformation by a six-membered ring, and the compound shows high binding affinity (Ki 0.01 nM).7 Besides the above steric restrictions, also the effect of electronic density distribution in a molecule on binding properties should be considered. Molecular probes to be used for in vivo imaging of protein aggregation in the central nervous system must be uncharged under physiological pH to pass the blood-brain barrier. However, efficient electron density delocalization from donor towards the acceptor group, resulting in substantial dipole moment of the molecule, a feature found in push-pull chromophores, enhances the binding affinity to protein aggregates and causes excitation and emission maxima to shift to longer wavelength.8 In this work we describe the synthesis of a novel FDDNP derivative 11, in which 3-fluoropyrrolidine ring formally replaces the (2-fluoroethyl)(methyl)amino group. We designed this molecule to enable investigation of a donor group's steric and electronic effects on protein labeling. The cyclic 3-fluoropyrrolidino group is more confor-mationally restricted than the acyclic (2-fluoroethyl) (methyl)amino group. To become coplanar with the naphthalene ring, mainly rotation around the N-C bond must occur. In the case of acyclic amines, coplanar conformation is attained by rotation around N-C and C-C bonds. This difference influences the binding properties as demonstrated in the case of non-fluorinated 6-(1-pyrro-lidinyl)- and 6-diethylamino-analogs of FDDNP, which show binding constants (Ki) of 0.19 and 0.46 nM, respectively.9 As far as the electronic effects are concerned, no major difference between the open-chain and cyclic analogs is expected because in both the arrangement of sub- stituents around the nitrogen is planar with the nitrogen lone electron pair perpendicular to the ring. In a coplanar conformation this is stereoelectronically favorable for an efficient delocalization of the electron density towards the acceptor group. We report on the chemical synthesis and characterization of 11, and on the procedure, which can be applied for the preparation of [18F]-labeled 11. The latter will be used for in vitro (autoradiography and binding affinity determinations) and in vivo (PET) assays of its ability to label tau (vs. amyloid) protein aggregates. 2. Results and Discussion The approach for the synthesis and radiolabeling of ^-substituted derivatives of DDNP (2)10 and FDDNP (1)11 was modified to enable the introduction of a 3-fluoropyr-rolidine moiety into the molecule and is summarized in Scheme 1. Starting 1-(6-hydroxynaphthalen-2-yl)ethanone (5) was prepared from commercially available 6-methoxy-de-rivative as reported previously.10 Naphthol 5 was subjected to the Bucherer reaction with 3-hydroxypyrrolidine to give the key intermediate 6 in 82% yield. The relatively high yield in comparison to the yields of analogous syntheses with 2-(ethylamino)ethanol or 4-hydroxy-methylpiperidine10 reflects smaller steric hindrance around the nitrogen atom in pyrrolidine ring than in the other two examples. The synthesis of unlabeled FDDNP analogue 11 to provide material for structural identification was carried out by fluorination of 6 with N,N-diethylamino-suflur trifluoride (DAST), followed by the Knoevenagel condensation of the intermediate fluoroketone 8 with ma-lononitrile. This procedure, although successfully yields substantial amounts of the compound, is not suitable for the production of radiolabeled material. For radiolabeling, the only viable sources of fluorine are cyclotron-produced either carrier-added [18F]F2 or no-carrier-added [18F]fluo- Scheme 1. a: pyrrolidin-3-ol/NaHSO3, b: CH2(CN)2/Py, c: Ts2O/Py, d: DAST/dichloromethane, e: KF/Kryptofix 2.2. ride ion, the latter being the reagent of choice.12 To examine the efficacy of nucleophilic substitution of a suitable leaving group at the position 3 in a pyrrolidine ring using naked fluoride ion, hydroxy compound 6 was first transformed into tosylate 7. The tosyloxy group can be efficiently replaced by fluoride in the presence of a potassium ion binding Kryptofix 2.2.2 to yield fluoroketone 8. This was important information, which we needed in order to design intermediates and procedure for radiolabel introduction in the last synthetic step.12 With this information at hand we first subjected the hydroxy intermediate 6 to the Knoevenagel condensation with malononitrile and then we transformed the obtained compound 9 into tosylate 10. With the latter we ran a test experiment under the reaction conditions as similar as possible to a radiolabe-ling procedure,11 but with "cold" [19F]KF. HPLC analysis provided the proof of the viability of the proposed radiola-beling method. In the chromatogram of the crude reaction mixture extract, a peak, eluting at 9.75 min was assigned to 11 based on the increase of the peak area in the chroma-togram after the original sample was spiked with an authentic sample of 11, prepared earlier (Figure 2.) Figure 2. A) HPLC analysis of the reaction mixture after the tosylate 10 reacted with fluoride ion under standard radiolabeling reaction conditions. B) HPLC analysis of the same reaction mixture after it was spiked with authentic 11. 3. Conclusions A novel FDDNP analog, {1-[6-(3-fluoropyrrolidin-1-yl)-2-naphthyl]ethylidene}malononitrile, was prepared and chemically characterized. Compound 1-[6-(2,2-dic-yano-1-methylvinyl)-2-naphthyl]pyrrolidin-3-yl 4-me-thylbenzenesulfonate was synthesized to provide a key intermediate for radiolabeling with [18F]fluoride ion. The radiolabeling procedure was tested starting from the prepared intermediate and [19F]KF. It has been proven that under the described conditions the title compound is for- med and this procedure can be used for the preparation of radiolabeled material. 4. Experimental NMR spectra were recorded on a Bruker DPX 300 or Bruker Avance III 500 spectrometers at 302 K using CDCl3 as the solvent. 1H chemical shifts are quoted in parts per million (ppm) downfield from TMS as internal standard, 13C NMR spectra are referenced to the middle line of CDCl3 signal (77.0 ppm), and 19F NMR spectra are referenced to external CFCl3. Mass spectra were measured at the Jožef Stefan institute using VG-Analytical Au-tospecQ spectrometer. Melting points were determined on a Kofler hot stage apparatus and are uncorrected. Elemental analyses were determined at the Faculty of Chemistry and Chemical Technology of the University of Ljubljana using a Perkin-Elmer 2400 CHN elemental analyzer. Radial chromatography was performed using Chromatotron (T-Squared Technology, Inc., 903 Sneath Lane, Suite 125 San Bruno, Ca 94066). The rotors were prepared as recommended by the manufacturer using E. Merck Silica Gel (Cat. No. 7749-3) in 1, 2, or 4 mm layer thicknesses. 1-[6-(3-Hydroxypyrrolidin-1-yl)-2-naphthyl]ethano ne (6). In a steel bomb 1-(6-hydroxy-2-naphthyl)ethanone (5, 358 mg, 1.92 mmol), pyrrolidin-3-ol13 (1.72 g, 19.7 mmol), and NaHSO3 (1.01 g) were mixed with water (10 mL) and heated in an oil bath at 135-140 °C for 42 hrs. The bomb was cooled, the content diluted with water (250 mL) and extracted with ethyl acetate (5 x 50 mL). Combined organic extract were dried with anhydrous sodium sulfate, filtered, and evaporated under reduced pressure. The residue was extracted with boiling ethanol (40 mL), the solution was filtered, and the filtrate was allowed to cool. From the solution the product separated as yellow plates, which were filtered off and dried to yield 401 mg (82%) of the title compound; mp 225-227 °C; Anal. Calcd. for C16H17NO2: C 75.27, H 6.71, N 5.49. Found: C 75.76, H 6.67, N 5.54; 1H NMR (300.13 MHz, CDCl3, TMS): 8 1.71 (d, 1H, J3,OH = 4.5 Hz, OH), 2.10-2.30 (m, 2H, H-4'), 2.66 (s, 3H, COCH3), 3.40-3.75 (m, 4H, H-5' and H-2'), 4.69 (m, 1H, H-3'), 6.74 (d, 1H, J57 = 2.3 Hz, H-5), 7.01 (dd, 1H, J57 = 2.3 Hz, J7 8 = 9.0 Hz, H-7), 7.62 (d, 1H, J34 = 8.7 Hz, H-4), 7.80 (d, 1h, J78 = 9.0 Hz, H-8) 7.92 (dd, 1H, J34 = 8.7 Hz, J13 = 1.9 Hz, H-3), 8.31 (d, 1H, J13 = 1.9 Hz, , H-1); 13C NMR (75.476 MHz, CDCl3, tms): 8 26.4, 34.3, 45.7, 56.3, 71.2, 104.7, 116.1, 124.73, 125.0, 125.9, 130.5, 130.6, 131.0, 137.8, 147.6, 197.7. 1-(6-Acetyl-2-naphthyl)pyrrolidin-3-yl-4-methylben-zenesulfonate (7). To a solution of 6 (64 mg, 0.251 mmol) in pyridine (3 mL) Ts2O (368 mg 1.13 mmol) was added in one por- a) b) 11 spiked with an authentic sample tion. The solution was stirred at rt for 30 min, concentrated under reduced pressure, and the residue was separated by radial chromatography (1 mm silicagel, petroleum ether : dichloromethane = 1 : 9). Fractions, containing the product were combined, concentrated, and the residue was crystallized from dichloromethane/petroleum ether mixture to obtain 43 mg (42%) of compound 7; mp 168171 °C; Anal. Calcd. for C23H23NO4S: C 67.46, H 5.66, N 3.42. Found: C 67.52, H 5.74, N 3.36; 1H NMR (300.13 MHz, CDCl3, TMS): 8 2.19-2.37 (m, 2H, H-4'), 2.44 (s, 3H, Ar-CH3), 2.66 (s, 3H, -COCH3), 3.50-3.72 (m, 4H, H-2' and H-5'), 5.28 (m, 1H, H-3'), 6.67 (dd, 1H, J57 = 2.6 Hz, H-5), 6.93 (dd, 1H, J57 = 2.6 Hz, J7 8 = 8.9 Hz, H- 7), 7.35 (m, 2H, -OTs), 7.60 (d, 1H, J34 = , 8.8 Hz, H-4), 7.80 (m, 3H, H-8 and -OTs), 7.92 (dd, 1H, J13 = 1.8 Hz, J34 = 8.8 Hz, H-3), 8.31 (d, 1H, J13 = 1.8 Hz, H-1). 13C nMr (126 MHz, CDCl3) 8 21.66,, 26.42, 31.98, 45.47, 53.70, 77.23, 80.45, 1(35.05, 115.90, 124.72, 125.18, 125.97, 127.71, 129.99, 130.53, 130.77, 131.02, 133.73, 137.53, 145.11, 146.66, 197.67. 1-[6-(3-Fluoropyrrolidin-1-yl)-2-naphthyl]ethanone (8). a) Kryptofix 2.2.2 (30.8 mg, 0.082 mmol) and KF (27.4 mg, 0.47mmol) were dissolved in deionized water (Millipore, 18 MQ; 0.5 mL) and evaporated to dryness. Residual water was removed by co-distillation with aceto-nitrile (8 x 1 mL). To the dried material compound 7 (16 mg, 0.039 mmol) and acetonitrile (2 mL) were added. The reaction mixture was stirred and heated under argon at 92-100 °C for 3 hrs. The product 8 (4 mg, 40%) was isolated by radial chromatography (1 mm silicagel, dichloro-methane : petroleum ether = 8 : 2). b) The solution of 6 (127.7 mg, 0.50 mmol) in dichloromethane (15 mL) in a round-bottom flask, equipped with a septum was purged with argon, and DAST (diethylamino-sulfur trifluoride; 102 pl, 0.78 mmol) was drop wise added. Stirring under argon was continued for additional 90 min. The reaction mixture was then poured into a mixture of ice and water, the solution was neutralized by the addition of solid NaHCO3, and extracted with dichloromethane (3 x 50 mL). Organic extracts were combined, dried with anhydrous sodium sulfate, and concentrated under reduced pressure. Compound 8 (60 mg, 47%) was obtained by radial chroma-tography (1 mm silicagel, dichloromethane) and crystallized from ethanol; mp 171-172 °C; Anal. Calcd. for C16H16FNO: C 74.69, H 6.27, N 5.44. Found: C 74.98, H 6.13, N 5.48; 1H NMR (300.13 MHz, CDCl3, TMS): 8 2.08-2.51 (m, 2H, H-4'), 2.66 (s, 3H, COCH3), 3.58-3.76 (m, 4H, H-2' and H-5'), 5.43 (m, 1H, JF3, = 51.6 Hz, H-3'), 6.75 (d, 1H, J13 = 1.5 Hz, H-5), 7.01 (dd, 1H, J57 = 2.3 Hz, J78 = 9.0 Hz', H-7), 7.63 (d, 1H, J3 4 = 8.7 Hz, H-4), 7.81 (d, 111, J7 8 = 9.0 Hz, H- 8), 7.93 (dd, 1H, J13 = 1.5 Hz, J34 = 8.7 Hz, H-3), 8.32 (d, 1H, J13 = 1.5 Hz, H-1); 13C NMR (75.476 MHz, CDCl3, TMS): 8 26.8, 32.8 (d, 2JCF = 23.3 Hz), 45.9, 54.9 (d, 2JCF = 21.9 Hz), 93.2 (d, 1JCF = 176.2 Hz), 105.3, 116.4, 125.1, 125.5, 126.3, 131.0, 131.1, 131.4, 138.1, 147.5, 198.0. {1-[6-(3-Hydroxypyrrolidin-1-yl)-2-naphthyl]ethylide-ne}malononitrile (9). A solution of the ketone 6 (50 mg, 0.19 mmol) and malononitrile (65 mg, 0.98 mmol) in pyridine (4 mL) was heated at 80 °C for 19 hrs. Pyridine was removed under reduced pressure and the residue was chromatographed by radial chromatography under argon (1mm silicagel, 1% methanol in dichloromethane). Fractions containing the product were combined and evaporated. The residue was dissolved in a small volume of benzene, the solution was transferred to a 5 mL beaker, and the beaker was placed in a chamber containing some hexane. The crystalline solid, which crystallized overnight, was filtered off to yield 40 mg (67%) of pure 9; mp 168-169 °C; Anal. Calcd. for C19H17N3O: C 75.23, H 5.65, N 13.85. Found: C 75.53, H 5.499, N 13.73; 1H NMR (300.13 MHz, CDCl3, TMS): 8 1.66 (d, 1H, J3' OH = 4.3 Hz, -OH), 2.10 to 2.31 (m, 2H, H-4'), 2.70 (s, 3H, -CH3), 3.42 to 3.59 (m, 2H, H-5'), 3.63 to 3.71 (m, 2H, H-2'), 43.70 (m, 1H, H-3'), 6.73 (d, 1H, J57 = 2.4 Hz, H-5), 7.03 (dd, 1H, J57 = 2.4 Hz, J7 8 = 9.0 Hz, , H-7), 7.57 (dd, 1H, J3 4 = 8.7 Hz, J13 = 1.9 Hz, H-3), 7.65 (d, 1H, J34 = 8.7 Hz, H-4), 7.77 (d, 1H, J78 = 9.0 Hz, H-8), 8.03 (id, 1H, J13 = 1.9 Hz, H-1). 13C NMR (126 MHz, CDCl3) 8 23.71, 34.20, 45.68, 56.27, 71.11, 80.76, 104.61, 113.97, 114.18, 116.70, 124.42, 124.95, 126.34, 127.98, 129.44, 130.81, 137.27, 147.81, 174.16. 1-[6-(2,2-Dicyano-1-methylvinyl)-2-naphthyl]pyrroli-din-3-yl 4-methylbenzenesulfonate (10). To a solution of 9 (48 mg, 0.16 mmol) in pyridine (1 mL) Ts2O (105 mg 0.32 mmol) was added in one portion. The solution was stirred at rt and after 30 min was concentrated under reduced pressure. The residue was suspended in water (40 mL) and extracted with dichloromethane (3 x 30 mL). Organic extracts were combined, dried with anhydrous sodium sulfate, evaporated under reduced pressure, and chromatographed by radial chromatography (1 mm silicagel, 1% methanol in dichloromethane) to yield 50 mg (69%) of pure compound 10; mp 54-60 °C; HRMS Calcd. for C26H23N3O3S: 457.1460. Found: 457.1471; 1H NMR (300.13 MHz, CDCl3, TMS): 8 2.17 to 2.40 (m, 2H, H-4'), 2.44 (s, 3H, Ar-CH3), 2.69 (s, 3H, C=C-CH3), 3.50 to 3.71 (m, 4H, H-2' and H-5'), 5.27 (m, 1H, H-33), 6.65 (d, 1H, J57 = 2.3 Hz, H-5), 6.93 (dd, 1H, J7 8 = 9.0 Hz, J57 = 2.3 Hz,' H-7), 7.34 (m, 2H, Ar), 7.55 (dd, 1H, J13 = 2.0 Hz, J34 = 8.7 Hz, H-3), 7.63 (d, 1H, J34 = 8.7 Hz3 H-4), 7.75 (d, 1H, J7 8 = 9.0 Hz, H-8), 7.81 (m, 2H, Ar), 8.01 (d, 1H, J1,3 = 2.0 Hz, H-1). {1-[6-(3-Fluoropyrrolidin-1-yl)-2-naphthyl]ethylide-ne}malononitrile (11). a) Compound 8 (30 mg, 0.12 mmol) and malononi-trile (39 mg, 0.59 mmol) were dissolved in pyridine (1 mL) and the solution was heated under argon at 85 °C for 23 hrs. Pyridine was removed under reduced pressure, the residue was dissolved in dichloromethane, and the solution was filtered through a cotton plug. The filtrate was concentrated and the product was isolated by radial chromatography (1 mm silicagel, dichloromethane : hexane = 5 : 1). Pure compound 11 was obtained after crystallization from a benzene solution in petroleum ether atmosphere (33 mg, 92%); mp 143-145.5 °C; Anal. Calcd. for C19H16FN3: C 74.74, H 5.28, N 13.76. Found: C 75.09, H 5.10, N 13.52; 1H NMR (300.13 MHz, CDCl3, TMS): 8 2.09-2.54 (m, 2H, H-4'), 2.70 (s, 3H, CH3), 3.60-3.80 (m, 4H, H-2' and H-5'), 5.44 (m, 1H, 2JF,H = 51.6 Hz, H-3'), 6.75 (d, 1H, J57= 2.3 Hz, H-5), 7.03 (eld, 1H, J57= 2.3 Hz, J7 8= 9.0 Hz, H-7), 7.57 (dd, 1H, J13 = 1.9 Hz, J34 = 8.8 Hz, H-3), 7.67 (d, 1H, J34 = 8.8 Hz, H-4), 7.78 (d, 1H, J78= 9.0 Hz, H-8), 8.04 (d, 1H, J13 = 1.9 Hz, H-1). 19F NMR (471 MHz, CDCl3) 8-175.351.13C NMR (126 MHz, CDCl3) 8 23.73, 24.20, 32.30 (d, 2JCF = 21.8 Hz), 45.49, 54.51(d, 2Jcf = 23.2 Hz), 80.98, 92.71 (d, 1JCF = 176.3 Hz), 104.822, 113.90, 114.11, 116.64, 124.45, 125.08, 126.41, 128.19, 129.37, 130.86, 137.18, 147.39, 174.22. b) Kryptofix 2.2.2 (15 mg, 0.04 mmol) and KF (10 mg, 0.17 mmol) were dissolved in deionized water (Milli-pore, 18 MQ; 1 mL) and evaporated to dryness. Residual water was removed by co-distillation with acetonitrile (8 x 1 mL). To the dried material, compound 10 (8 mg, 0.018 mmol) and acetonitrile (1 mL) were added. The reaction mixture was stirred and heated under argon at 90 °C for 30 min. After cooling, water was added (20 mL) and the mixture was applied to a Sep-pak C18 column, which was previously activated by thorough washing with water, methanol and finally with water. First the column was eluted with water (10 mL) to remove polar components, and then the less polar material was eluted with dichloromethane. The dichloromethane eluate was dried with anhydrous sodium sulfate, filtered, and analyzed by HPLC (250 x 5 mm Econosil Silica 10 pm, dichloromethane, UV/Vis detector set at 254 nm). Compound 11 was identified in the mixture by increased peak area in the chromatogram after previously synthesized compound 11 was added to the mixture. 5. Acknowledgment Financial support from the Slovenian Research Agency (Grant P1-0230) is acknowledged. The work was also partially supported with infrastructure of the EN-FIST Centre of Excellence, Dunajska 156, SI-1000 Ljub- ljana, Slovenia. JRB gratefully acknowledges the support of the Elizabeth and Thomas Plott Chair Endowment in Gerontology. 6. Supporting material Supporting material contains NMR spectra of compounds 7 - 11. This material is available free of charge via the Internet at http://acta.chem-soc.si/. 7. References 1 K. Shoghi-Jadid, G. W. Small, E. D. Agdeppa, V. Kepe, L. M. Ercoli, P. Siddarth, S. Read, N. Satyamurthy, A. Petric, S.-C. Huang, J. R. Barrio, Am. J. Geriatr. Psychiatry 2002, 10, 2435. 2 J. R. Barrio, N. Satyamurthy, S.-C. Huang, A. Petric, G. W. Small, V. Kepe, Acc. Chem. Res. 2009, 42, 842-850. 3 J. Shin, V. Kepe, G. W. Small, M. E. Phelps, J. R. Barrio, Intern. J. Alzheimer's Disease 2011, 687945. Epub 2011 Apr 19. PMID: 21629709. 4 J. R. Barrio, Y. Bordelon, G. W. Small, V. Kepe, Book of Abstracts AD/PD 2011, 36, Barcelona, Spain, March 2011. 5 M. Landau, M. R. Sawaya, K. F. Faull, A. Laganowsky, L. Jiang, S. A. Sievers, J. Liu, J. R. Barrio, D. Eisenberg, PLoS Biology 2011, 9(6): e1001080. doi:10.1371/journal.pbio. 1001080. 6 A. F. Jacobson, A. Petric, D. Hogenkamp, A. Sinur, J. R. Barrio, J. Am. Chem. Soc. 1996, 118, 5572-5579. 7 E. D. Agdeppa, V. Kepe, A. Petric, J. Liu, N. Satyamurthy, K. Shoghi-Jadid, G. W. Small, S.-C. Huang, J. R. Barrio, J. Nucl. Med. 2002, 43 (Supplement S), 166P. 8 S. J. Lord, N. R. Conley, H.-I. D. Lee, R. Samuel, N. Liu, R. J. Twieg, W. E. Moerner, J. Am. Chem. Soc. 2008, 130, 92049205. 9 Unpublished results in preparation for publication. 10 A. Petric A, T. Spes, J. R. Barrio, Monatsh. Chem. 1998,129, 777-786. 11 J. Liu, V. Kepe, A. Zabjek, A. Petric, H. C. Padgett, N. Satya-murthy, J. R. Barrio, Molec. Imag. Biol. 2007, 9, 6-16. 12 D. W. Kim, H.-J. Jeong, S. T. Lim, M.-H. Sohn, Nucl. Med. Mol. Imaging 2010, 44, 25-32. 13 Although commercially availbale (3R)-pyrrolidin-3-ol was used, we make no claims about the stereochemistry at the center of chirality. Povzetek Z namenom omogočiti raziskave vplivov strukturnih sprememb donorskega dela molekule na vezavne lastnosti s tau proteinskimi agregati, smo pripravili nov analog spojine FDDNP, v katerem je vlogo donorske skupine prevzela 3-fluo-ropirolidinska skupina ({1-[6-(3-fluoropirolidin-1-il)-2-naftil]etiliden}malononitril). Poročamo o sintezni poti, ki je primerna za sintezo neoznačene, kot tudi o sintezni poti za pripravo z radioaktivnim fluorom 18F označene spojine. Slednjo bo po opisani poti možno pripraviti z radioaktivnim fluorom, pridobljenim s ciklotronom in jo uporabiti pri raziskavah vezave na proteinske agregate. Supplementary Material ï ' ¡5 ' 5) ' S ' S ' U ' M ' si ' sï ' 5 ' ÏÔ ' S ' 10 ' S ' S ' 15 ' L0 ' ÔL! ' ïô ritom) 1H NMR spectrum of compound 7 210 200 190 180 170 160 150 110 130 120 110 100 90 80 70 60 SO 10 3« 20 10 1 -10 fl (ppm) f 1 T C Kj F J / r- - J / J i J J j J / 1 1 rl 1 1 J L , _J__1 1 ,1 I j 1 J \l w, J i J -r 1—i— :—' ' i • 1 1 ■- g ; s S g _ 3 5 f! tppm) 1H NMR spectrum of compound 8 fltppm] 19F NMR spectrum of compound 8 I "^CHj V J f ( f, i / J 111 1 | 11 ! 1 1 li J LJL T- V 2 S À s s?gs v r 9; 1 h 9 Y T 3 litem) 1H NMR spectrum of compound 9 fl (ppm) H,C N ¥ W \ if T T SCH, c i r / - f / i ' / L I f / 1 i I | r i A l , J I J J. '1 g sgg ? S s § s U> 3-5 U 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 Î.5 3.0 2.5 1.0 1.5 1,0 0J 0.0 II (cpm} 1H NMR spectrum of compound 10 Jt Y* [I I "'^CH F- i Jt J I ■ r / r /j [ J i ii J J / !/ J i 1 m 1 li i i , 1 1 il k-l 1 111 1 HjH (-y*V H|-t hyjl 1-yH T -r H i St "S S U> ' Si ' 10 ' 75 ' Ï5 ' M ' M ' is ' M ' « ' ta ' 3*5 ' î!Ô ' IS ' M ' l!s ' lï ' 05 ' M % > tf 1 1 r1 ^CHj F— c J j ! ■ ■ ■ ■ -- • ■ ftlppm) 19F NMR spectrum of compound 11 R 1 Î) X 1 g "l ï ass s as 1 lp mum T Q ss V 8K KE S" c * 1 fia V £3 V 9 \ "X F— c Pi | 210 200 190 180 1 70 160 150 M0 130 120 110 100 9 1 <0 70 60 ; 4 1 » 20 1 ■ - 0 fl(wm) 13C NMR spectrum of compound 11