Zhong-Yin Zhang,b Xin Zhouc and Zhong-Xing Jiang*acde
Fluorine is a highly attractive element for both medicinal chemistry and imaging technologies. To facilitate
protein tyrosine phosphatase (PTP)-targeted drug discovery and imaging-guided PTP research on fluorine,
several highly potent and 19F MR sensitive PTP inhibitors were discovered through a structure-based fo-
cused library strategy.
Introduction
PTPs play crucial roles in such fundamental cellular processesas proliferation, differentiation, survival, apoptosis, motilityand adhesion.1 Abnormal PTP activity is well known to be as-sociated with a broad spectrum of human diseases.2 As asuperfamily of more than 100 signalling enzymes, many PTPshave emerged as attractive drug targets, such as mPTPB fortuberculosis, SHP2 for many types of cancers, LYP for autoim-mune diseases, and PTP1B for type 2 diabetes, obesity andbreast cancer.3 To this end, the discovery of highly potent andspecific small-molecule PTP inhibitors and their applicationin probing the biological and pathological mechanisms ofPTPs, especially with the aid of modern imaging and spectro-scopy technologies, are the cornerstone for PTP-targeted drugdiscovery.
As a versatile element in biomedical research, fluorine haspromising utility in PTP-targeted drug discovery. On onehand, the introduction of fluorineIJs) into bioactive moleculesis usually accompanied by improved pharmacokinetic proper-ties and protein–ligand binding interactions.4 Thus, fluorina-
tion has become a routine strategy in drug discovery, andfluorinated compounds have made up over 20% of all phar-maceuticals. On the other hand, fluorinated molecules canbe monitored in vivo without ionizing radiation and back-ground signals by 19F magnetic resonance (19F MR) whichprovides high-contrast and non-invasive spectroscopy (19FNMR) and images (19F MRI). In recent years, 19F MRI/NMRhas been widely used in tracking targets of interest5 andmonitoring biological reactions.6 Therefore, the discovery offluorinated small-molecule PTP inhibitors with high 19F MRsensitivity may provide easy access to PTP-targeted drugs anddetailed understanding of PTPs' biological and pathologicalmechanisms.
A recent discovery of a 19F MRI sensitive salinomycin deriv-ative with specific toxicity towards cancer cells7 by this groupprompted us to develop novel fluorinated PTP inhibitors.Herein, ortho-bisIJtrifluoromethyl)carbinol phenol was designedas a novel chemical scaffold for 19F MRI sensitive PTP inhibi-tors (Scheme 1). Due to the strong electron-withdrawing abilityof 2 trifluoromethyl groups, bisIJtrifluoromethyl)carbinol is aweak acid and is therefore a suitable substitute for the carbox-ylic group in salicylic acid from which a number of highly po-tent and selective PTP inhibitors have recently been discovered.8
Consequently, the ortho-bisIJtrifluoromethyl)carbinol phenolsmay mimic the well-established binding mode of salicylic acid-
a School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China.
E-mail: [email protected] of Medicinal Chemistry and Molecular Pharmacology, Center for
Cancer Research, Purdue University, West Lafayette, Indiana 47907, USAc State Key Laboratory for Magnetic Resonance and Atomic and Molecular Physics,
Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences,
Wuhan 430071, ChinadKey Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute
of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, Chinae State Key Laboratory for Modification of Chemical Fibers and Polymer
Materials, Donghua University, Shanghai 201620, China
† The authors declare no competing interests.‡ Electronic supplementary information (ESI) available: Copies of 1H NMR, 13CNMR, 19F NMR and HRMS of compounds, and single-crystal X-raydiffractograms of 7c. CCDC 1470244. For ESI and crystallographic data in CIF orother electronic format see DOI: 10.1039/c6md00277c Scheme 1 Design of 19F MR sensitive PTP inhibitors.
based inhibitors at the highly positively charged active site ofPTPs.8 It is noteworthy that the 6 symmetric fluorines inbisIJtrifluoromethyl)carbinol, which were recently employed inthe construction of highly 19F MRI sensitive dendritic drug deliv-ery vehicles,9 aggregately provide a strong 19F MR signal for conve-niently probing the mode of interaction and related biological re-actions using 19F NMR and 19F MRI. Moreover, cell permeabilityis a challenge for PTP inhibitors. BisIJtrifluoromethyl)carbinol-based PTP inhibitors without a negative charge may exhibit favor-able cell permeability, bioavailability and pharmacokinetic proper-ties by the introduction of hydrophobic trifluoromethyl groups.4
Materials and methodsChemistry general information1H, 19F and 13C NMR spectra were recorded at 400 MHz.Chemical shifts (δ) are in ppm and coupling constants (J) arein Hertz (Hz). 1H NMR spectra were referenced to tetra-methylsilane (d, 0.00 ppm) using CDCl3, acetone-d6 orDMSO-d6 as solvents. 13C NMR spectra were referenced tosolvent carbons (77.16 ppm for CDCl3, 29.84, 206.26 ppm foracetone-d6 and 39.52 ppm for DMSO-d6).
19F NMR spectrawere referenced to 2% perfluorobenzene (s, −164.90 ppm).The splitting patterns for 1H NMR spectra are denoted as fol-lows: s (singlet), d (doublet), q (quartet), m (multiplet), dd(doublet of doublets), and td (triplet of doublets). High reso-lution mass spectra were recorded using electron spray ioni-zation (ESI).
Unless otherwise indicated, all reagents were obtainedfrom a commercial supplier and used without prior purifica-tion. DCM and DMF were dried and freshly distilled prior touse. Flash chromatography was performed using silica gel(200–300 mesh) with either petroleum ether/EtOAc aseluents.
Synthesis of compounds
Phenol 1c. Hexafluoroacetone trihydrate (9.71 g, 6.1 mL,44.1 mmol) was dried over concentrated sulfuric acid and theresulting anhydrous hexafluoroacetone was bubbled into asolution of 4-phenylphenol (5.00 g, 29.4 mmol) and alumin-ium chloride (0.39 g, 2.94 mmol) in 1,2-dichloroethane (250mL) slowly. After the addition, the mixture was heated underreflux at 80 °C until 4-phenylphenol was consumed, as indi-cated by TLC. The reaction mixture was then cooled to rt,washed with 2 N HCl (100 mL) and extracted with DCM (50mL × 2). The combined organic layers were dried overanhydrous Na2SO4, concentrated under vacuum and purifiedby flash chromatography using silica gel (5% EtOAc/petro-leum ether) to give 1c as white wax (3.6 g, 85% yield). 1HNMR (CDCl3, 400 MHz) δ 7.00 (d, J = 8.5 Hz, 1H), 7.35 (t, J =7.2 Hz, 1H), 7.44 (t, J = 8.0 Hz, 2H), 7.48–7.54 (m, 2H), 7.57(dd, J = 8.5, 2.1 Hz, 1H), 7.66 (s, 1H); 19F NMR (CDCl3, 376MHz) δ −78.53; 13C NMR (acetone-d6, 100 MHz) δ 80.0–81.2(m), 116.0, 119.5, 124.2 (q, J = 286 Hz), 127.4, 127.7, 128.2,129.9, 131.0, 134.7, 140.7, 156.6; HRMS (ESI) calcd forC15H11F6O2
+ ([M + H]+) 337.0658, found 337.0671.
Phenol 1a. Phenol 1a was prepared from benzene (0.80 g, 10.2mol) by following the general procedure as clear oil (2.5 g, 30%yield). 1H NMR (CDCl3, 400 MHz) δ 7.39–7.53 (m, 3H), 7.73 (dd,J = 7.4, 0.9 Hz, 2H); 19F NMR (CDCl3, 376 MHz) δ −78.69.
Phenol 1b. Phenol 1b was prepared from p-cresol (3.0 g,27.7 mmol) by following the general procedure as white wax(6.1 g, 80% yield). 1H NMR (CDCl3, 400 MHz) δ 2.31 (s, 3H),6.16 (s, 1H), 6.81 (d, J = 8.3 Hz, 1H), 6.88 (s, 1H), 7.15 (dd, J =8.3, 1.6 Hz, 1H), 7.23 (s, 1H); 19F NMR (CDCl3, 376 MHz) δ−78.64.
Phenol 1d. Phenol 1d was prepared from [1,1′-biphenyl]-3-ol (5.00 g, 29.4 mmol) in the same manner as described for1c (8.6 g, 87% yield). 1H NMR (CDCl3, 400 MHz) δ 7.13 (d, J =1.8 Hz, 1H), 7.19–7.26 (m, 1H), 7.35–7.47 (m, 3H), 7.47–7.59(m, 3H); 19F NMR (CDCl3, 376 MHz) δ −78.72; 13C NMR (ace-tone-d6, 100 MHz) δ 79.9–81.1 (m), 114.5, 117.0, 120.2, 124.2(q, J = 286 Hz), 128.8, 129.1, 129.9, 140.0, 145.3, 157.5; HRMS(ESI) calcd for C15H11F6O2
+ ([M + H]+) 337.0658, found337.0651.
Phenol 1e. Phenol 1e was prepared from [1,1′-biphenyl]-2-ol (5.00 g, 29.4 mmol) in the same manner as described for1c (3.6 g, 74% yield). 1H NMR (CDCl3, 400 MHz) δ 7.11 (t, J =7.9 Hz, 1H), 7.35 (dd, J = 7.5, 1.5 Hz, 1H), 7.43–7.50 (m, 3H),7.50–7.59 (m, 3H); 19F NMR (CDCl3, 376 MHz) δ −78.41; 13CNMR (acetone-d6, 100 MHz) δ 80.6–81.8 (m), 115.5, 121.4,124.1 (q, J = 286 Hz), 128.2, 128.3, 129.2, 130.5, 133.1, 133.8,138.4, 154.9; HRMS (ESI) calcd for C15H11F6O2
Naphthol 4. To an ice-cold suspension of diol 3 (2.40 g,7.36 mmol) in trifluoroacetic acid, acetone (2.2 mL, 29.5mmol) was added and then TFA (10.8 mL, 145.87 mmol) wasadded to the mixture dropwise. The reaction mixture waswarmed slowly to rt and then stirred for 48 h. After evapora-tion of the solvent, the residue was purified by flash chroma-tography using silica gel (2% EtOAc/petroleum ether) to give4 as white wax (0.85 g, 34% yield). 1H NMR (acetone-d6, 400MHz) δ 1.61 (s, 6H), 7.11–7.24 (m, 2H), 7.34 (s, 1H), 7.95 (d, J= 8.8 Hz, 1H), 8.09 (s, 1H); 19F NMR (acetone-d6, 376 MHz) δ−78.30; 13C NMR (acetone-d6, 100 MHz) δ 27.0, 76.6–77.8 (m),102.8, 108.5, 110.0, 113.7, 119.2, 123.2 (q, J = 287 Hz), 125.2,128.4, 131.6, 138.0, 150.0, 158.5; HRMS (ESI) calcd forC16H13F6O3
+ ([M + H]+) 367.0763, found 367.0773.Ester 8. To a solution of 4 (470.0 mg, 1.28 mmol) and
methyl bromoacetate (588.7 mg, 3.85 mmol) in acetone,K2CO3 (381.5 mg, 3.85 mmol) was added and then the reac-tion mixture was heated under reflux until 4 was consumed,as indicated by TLC. After removal of the solvent under re-duced pressure, the residue was dissolved in EtOAc (20 mL)and washed with water (50 mL × 2). The organic layer wasdried over anhydrous Na2SO4, concentrated under vacuumand purified by flash chromatography using silica gel (2%EtOAc/petroleum ether) to give ester 8 as light yellow oil(480.0 mg, 86% yield). 1H NMR (CDCl3, 400 MHz) δ 1.60 (s,6H), 3.83 (s, 3H), 4.76 (s, 2H), 6.96 (d, J = 2.4 Hz, 1H), 7.19(dd, J = 9.0, 2.5 Hz, 1H), 7.29 (s, 1H), 7.78 (d, J = 9.0 Hz, 1H),7.99 (s, 1H); 19F NMR (CDCl3, 376 MHz) δ −78.24; 13C NMR(CDCl3, 100 MHz) δ 26.8, 52.4, 65.2, 76.0–76.6 (m), 101.8,105.5, 113.6, 118.3, 122.1 (q, J = 287 Hz), 125.1, 127.6, 130.7,136.2, 149.5, 157.5, 169.0; HRMS (ESI) calcd for C19H17F6O5
+
([M + H]+) 439.0975, found 439.0981.Acid 9. Ester 8 (400.0 mg, 0.91 mmol) was dissolved in
THF/H2O (5 mL/5 mL) and the solution was stirred at 0 °C.Then, NaOH (43.8 mg, 1.10 mmol, 10 N aqueous solution)was added at 0 °C. The reaction mixture was stirred at rtuntil 8 was consumed, as indicated by TLC. The solutionwas acidified to pH 6.0 and then extracted with EtOAc (20mL × 2) and washed with water (10 mL). The organic layerwas dried over anhydrous Na2SO4 and concentrated undervacuum to give acid 9 as white wax (370 mg, 96% yield).1H NMR (CDCl3, 400 MHz) δ 1.60 (s, 6H), 4.82 (s, 2H), 6.99(d, J = 2.4 Hz, 1H), 7.19 (dd, J = 9.0, 2.5 Hz, 1H), 7.29 (s,1H), 7.79 (d, J = 9.1 Hz, 1H), 7.99 (s, 1H); 19F NMR (CDCl3,376 MHz) δ −78.33; 13C NMR (acetone-d6, 100 MHz) δ 27.0,65.4, 76.6–77.8 (m), 102.9, 106.6, 111.0, 114.6, 119.5, 123.2(q, J = 286 Hz), 126.0, 128.4, 131.5, 137.6, 150.2, 159.0,170.0; HRMS (ESI) calcd for C18H15F6O5
+ ([M + H]+)425.0818, found 425.0798.
Amide 7a. Potassium carbonate (170.0 mg, 1.23 mmol)was added to a solution of 4 (150.0 mg, 0.41 mmol) and 6a(111.6 mg, 0.62 mmol) in acetone (5 mL) and then theresulting suspension was heated under reflux until 4 wasconsumed, as indicated by TLC. After removal of the sol-vent under reduced pressure, the residue was dissolved inEtOAc (25 mL) and then washed with 2 N HCl (30 mL) and
brine (30 mL × 2). The organic layer was dried overanhydrous Na2SO4, concentrated under vacuum and usedwithout purification. The residue was dissolved in TFA/H2O(9/1, 11.3 mL); then, anisole (45 μL) was added and theresulting mixture was stirred overnight. The reaction mix-ture was concentrated under vacuum and then diluted withEtOAc (25 mL) and washed with brine (30 mL × 2). The or-ganic layer was dried over anhydrous Na2SO4, concentratedunder vacuum and purified by flash chromatography usingsilica gel (20–80% EtOAc/petroleum ether) to give 7a asclear oil (131 mg, 77% yield). 1H NMR (acetone-d6, 400MHz) δ 0.88 (t, J = 7.4 Hz, 3H), 1.41–1.66 (m, 2H), 3.24–3.31 (m, 2H), 4.64 (s, 2H), 7.09–7.25 (m, 2H), 7.42 (s, 1H),7.91 (d, J = 9.0 Hz, 1H), 8.09 (s, 1H); 19F NMR (acetone-d6,376 MHz) δ −76.08; 13C NMR (acetone-d6, 100 MHz) δ 11.1,23.0, 41.0, 67.4, 79.7–80.3 (m), 105.4, 111.9, 114.8, 117.8,123.6 (q, J = 286 Hz), 124.1, 129.5, 130.8, 136.6, 154.4,157.8, 168.6; HRMS (ESI) calcd for C18H18F6NO4
Amide 7q. Amide 7q was prepared from 9 (200.0 mg, 0.47mmol) in the same manner as described for 7m (126 mg,76% yield). 1H NMR (acetone-d6, 400 MHz) δ 5.09 (s, 2H),
19F MRI experiments19F MRI experiments were performed on a 9.4 T micro-imaging system with a 10 mm inner diameter 19F coil (376.4MHz) for both radiofrequency transmission and reception.The MSME (Multi-Slice Multi-Echo) pulse sequence wasemployed for all MRI acquisitions with a single average. FOV= 8 × 8 mm2, SI = 40.0 mm TR = 2500 ms and TE = 7.6 mswere used. The data collection time was 160 ms.
Computational analysis
For computational analysis, PDB code 3O5X was used as amodel structure. Molecular docking was carried out usingAutoDock Vina. The small molecule binding mode wasmodelled manually using Moloc (Gerber Molecular Design,Switzerland). The image was produced by using PyMOL.
PTP activity assay
PTP activity was assayed using p-nitrophenyl phosphate(pNPP) as a substrate in 3,3-dimethylglutarate buffer (50 mM3,3-dimethylglutarate, pH 7.0, 1 mM EDTA, 150 mM NaCl) at25 °C. The library compounds were screened using a 96-wellformat. The amount of the p-nitrophenol product was deter-mined from the absorbance at 405 nm detected using a Spec-tra MAX340 microplate spectrophotometer (Molecular De-vices). The nonenzymatic hydrolysis of pNPP was corrected by
Scheme 2 Synthesis of the bisIJtrifluoromethyl)carbinol library.
Table 1 IC50 (μM) of 1a–g for a selected panel of PTPs
measuring the control without the addition of an enzyme. AllPTPs used in the study were recombinant proteins preparedin-house.
Results and discussion
To probe the structure–activity relationship of the ortho-bisIJtrifluoromethyl)carbinol phenol-based inhibitors, astructure-based focused library strategy was employed. Ourinitial effort involved the construction of a focused library of7 bisIJtrifluoromethyl)carbinol-substituted benzene to identifythe optimal relative positions for these substituents(Scheme 2). Through the Lewis acid-catalysed Friedel–Craftsreaction, the bisIJtrifluoromethyl)-carbinol moiety was conve-niently anchored to benzene, phenols, and naphthols in goodyields. Due to the strong directing effect of the phenolic hy-droxyl group, the desired ortho-bisIJtrifluoromethyl)carbinolphenols were isolated as the major products (1b–g).
The ability of library compounds 1a–g to inhibit a se-lected panel of PTPs of therapeutic interest, includingmPTPB, SHP2, PTP1B, CD45, LYP, and FAP-1, was assessedat pH 7 and 25 °C (Table 1). The results indicate that the phe-nolic hydroxyl group plays a crucial role in PTP bindingthrough which the inhibitors may mimic the binding modeof salicylic acid-based inhibitors. No appreciable activitywas found for 1a, which lacks a phenolic hydroxyl group inthe scaffold. The PTP inhibitory activity is also very sensi-tive to the size and position of the substituent. Neither 1cwith a para-phenyl group nor 1d with a meta-phenyl grouphas appreciable activity, while 1b with a small-sizedpara-methyl group has moderate activity. Among the librarycompounds 1a–g, 2-naphthol derived 1f is the most potentone for the selected panel of PTPs, which was then selectedfor further optimization.
To further improve the potency and selectivity, 1f wasmodified into a focused library to target both the activesite and a peripheral secondary binding site of PTPs(Scheme 3).8,10 Starting from 2,7-naphthalene-diol 2, a corecompound 3, with an extra 7-hydroxyl group compared to1f, was constructed through Friedel–Crafts reaction ingood yield. Then, a panel of amines 5a–r with structuraldiversity were selected for the construction of side chains6a–r by reaction with bromoacetyl bromide, respectively.After protecting the 2 neighbouring hydroxyl groups in 3with acetones, side chains 6a–r were anchored to the 7-hy-droxyl group in 4 in the presence of K2CO3 to give esterintermediates, after which the acetonide protecting groupwas removed with TFA to give amides 7a–p in good yieldsover 2 steps. However, the preparation of 7m, 7q and 7rwas unsuccessful. So, an alternative method was developedby first anchoring an acetic acid side chain to 4 and thencoupling amines 5m, 5q, and 5r, respectively, to give thecorresponding amides 7m, 7q, and 7r. In this way, the fo-cused library of 18 ortho-bis(trifluoromethyl)carbinol phe-nols 7a–r with an amide side chain was convenientlyprepared.
To illustrate the structures of ortho-bisIJtrifluoromethyl)carbinol phenols 7a–r, a single-crystal X-ray structureof 7c was obtained (Fig. 1). However, many attempts to pre-pare a single-crystal of 7p were unsuccessful.
As expected, the activities of library compounds 7a–r aremuch higher than those of 1f (Table 2). Compound 7r with asulfonohyrazide side chain was identified as a highly potentand selective mPTPB inhibitor with an IC50 value of 2.3 μM
Scheme 3 Synthesis of a focused library of PTP inhibitors.
and more than 7-fold selectivity compared to SHP2, PTP1B,CD45, LYP, and FAP-1. It is interesting to point out that mostof aliphatic amine derived compounds 7a–c and 7e–g showno appreciable PTP inhibitory activity, while bulky aliphaticamine derived compounds 7d, 7h, and 7i exhibit moderateactivities. In contrast, most of aromatic amine derived com-pounds 7j–r have good activities and selectivity except for thepositively charged 7m. Among them, compound 7p with abulky aromatic group on the side chain exhibits very high ac-tivity toward the selected panel of PTPs with an IC50 valueranging from 2.2 μM for FAP-1 to 6.6 μM for PTP1B. Basedon these observations, it is obvious that the potency of ortho-bisIJtrifluoromethyl)carbinol phenol-based inhibitors can beconsiderably optimized up to 58-fold by tethering an amideside chain. A bulky aromatic group-containing side chain, i.e.7l and 7p, can efficiently promote the binding affinity be-tween PTPs and inhibitors by interacting with a peripheralpocket in the vicinity of the PTP active sites, probablythrough steric effects and π–π stacking.
Computational analysis of the binding activity of 7p in thehighly conservative active site of PTPs provided some insightinto the structure–activity relationship between these novelinhibitors and PTPs. Oncogenic SHP2 with a known complexstructure (PDB ID: 3O5X) was selected as a model. Fig. 2shows the binding mode of 7p with SHP2 compared to thatof a known salicylic acid-based SHP2 inhibitor 10 which hasan IC50 of 5.5 μM toward SHP2.8a As expected, the ortho-bisIJtrifluoromethyl)carbinol phenol moiety can mimic thebinding mode of salicylic acid by interacting with the corre-sponding amino acid residues Trp423, Arg465 and Gln510(the distances between O of ortho-bisIJtrifluoromethyl)carbinoland the three hydrogen bonding heavy atoms of the residuesare 3.6 Å). However, due to the difference in molecular geom-etry, the side chains of 7p and 10 interacted with SHP2 in dif-ferent ways. Instead of interacting with Arg362 and Lys364 ofSHP2, the aromatic side chain in 7p has a strong π–π interac-tion with Tyr-279.
Finally, the 19F magnetic resonance properties of PTP in-hibitors 7a–r were investigated. As designed, all 6 symmetri-cal fluorines in 7a–r generated a strong singlet 19F NMR sig-nal, respectively (Fig. 3). Unified 19F signal dramaticallyimproved the 19F NMR sensitivity of these fluorinated inhibi-
tors for downstream applications. Then, 7p, with a high po-tency toward a panel of PTPs, was selected for the 19F MRIstudy. It was found that 7p has a very short longitudinal re-laxation time T1 of 299 ms, which could further improve its19F MRI sensitivity by allowing the collection of more tran-sient signals without prolonging the data acquisition time.The 19F MRI phantom experiment on an array of 7p solutionsindicated that 7p could be clearly imaged by 19F MRI with ascan time of 120 seconds at a concentration of as low as 8.3mM (or 50 mM in 19F concentration, Fig. 3). Therefore, 7p isa novel PTP inhibitor as well as a highly valuable tool mole-cule whose local information, such as distribution and con-centration, and interactions with PTPs, such as the bindingmode and affinity, can be conveniently monitored by 19F MRspectroscopy and imaging without extra modification in theabsence of background signals.
Conclusions and outlook
In summary, we have successfully demonstrated a strategyfor developing novel 19F magnetic resonance sensitive smallmolecule PTP inhibitors for drug discovery and biomedicalresearch through rational molecular design and symmetricalfluorination. ortho-BisIJtrifluoromethyl)carbinol phenol isa valuable substitute for salicylic acid in PTP inhibitor dis-covery, which successfully integrates the PTP binding abilityand high 19F NMR signal generating ability. As fluorinateddrugs are booming in pharmaceutical industry, it is ofgreat importance to utilize their inherent 19F magnetic reso-nance properties in target identification, pharmacologystudy, in vivo drug tracking, image/spectroscopy-guideddrug therapy and beyond.
Finally, we want to point out that both 19F NMR and 19FMRI are valuable modalities for biomedical research. 19F MRIprovides high-contrast images at 19F concentrations of mMand above, while 19F NMR provides sensitive spectroscopyeven at sub-μM 19F concentrations. To improve the PTP inhi-bition potency and selectivity, studies on the 19F MRI sensi-tivity of these inhibitors and their application in the 19F mag-netic resonance-guided PTP mechanism are currently inprogress and will be published in due course.
We are thankful for financial support from the National Natu-ral Science Foundation of China (21372181, 21402144,21572168, and 21575157), Key Laboratory of Synthetic Chem-istry of Natural Substances (Shanghai Institute of OrganicChemistry) and State Key Laboratory for Modification ofChemical Fibers and Polymer Materials (Donghua University).LW and ZYZ are supported by NIH RO1 CA69202 and P30CA023168.T
able
2IC
50(μM)of7a
–rforaselected
pan
elofPTPs
7a–c
7d7e–f
7g7h
7i7j
7k7l
7m7n
7o7p
7q7r
mPT
PB—
——
18.1
±9.5
5.1±0.4
9.4±0.2
14.4
±1.9
7.3±0.5
4.8±0.1
—4.7±0.2
—2.9±0.1
2.6±0.1
2.3±0.1
SHP2
—9.0±2.2
——
6.7±1.2
6.9±1.4
19.0
±25
.68.5±1.4
3.5±0.5
——
19.5
±47
.83.2±0.3
12.8
±3.6
20.3
±18
.6PT
P1B
—14
.7±3.0
——
12.6
±4.8
13.8
±2.0
17.2
±8.9
——
——
6.6±1.3
——
CD45
—7.6±0.8
——
5.2±0.6
6.6±0.6
—7.8±0.5
3.4±0.2
—29
.1±38
.214
.9±7.2
2.8±0.2
10.9
±1.4
16.1
±5.0
LYP
—10
.1±0.8
——
6.9±1.1
7.5±0.8
—8.8±1.1
——
—20
.6±35
.93.4±0.3
14.3
±3.1
15.4
±3.1
FAP-1
—7.4±0.8
——
4.3±1.8
5.6±0.7
—6.5±0.7
2.8±0.3
——
12.4
±8.3
2.2±0.3
9.9±1.5
14.9
±5.2
A“—
”indicates
IC50≫
20μM.
Fig. 2 The calculated structure of 7p bound to SHP2 compared with asalicylic acid-based inhibitor 10.
Fig. 3 19F NMR of selected inhibitors (upper) and 19F MRI of 7p(lower).
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