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Short Stories in Pharmaceutical Discovery, Process and Isotopic Short Stories in Pharmaceutical Discovery, Q. Michaudel Process and Isotopic Labeling Baran Lab GM 2011-11-19 Some data about some common radiolabels: There are three different but complementary ways to explore medicinal chemistry, every having its own constraints: Isotope Type Decay Half-life Medical use Discovery, hit-to-lead, and lead optimization: * rapidity * development of a chemical library 3 natural 3He, – 12.32 years analytical Process chemistry and development: * scalable synthesis (yield optimization, ease of T (trace) β purification, cost, safety) for bulk industrial production 11C artificial 11B, β+ 20.38 min PET imaging Isotopic labeling: * availability and price of labeled reagents * reaction times for radiochemistry (tomography...) natural 14 14N, β– 5,730 ± 40 analytical C (trace) years Route Discovery Process Labeling 13N artificial 13C, β+ <10 min PET imaging 15 15 + Typical O artificial N, β 122 s PET imaging scale 1 mg < x < 1 kg > 100 kg ~100 mg synthesis 18F artificial 18O, β+ 109.77 min PET imaging Isotopic labeling synthesis, a few definitions: 99mTc artificial 99Tc, γ 6.01 h imaging This technique is used for metabolic and pharmacological studies. Radiolabeled compounds allow for measuring absorption, distribution, metabolism, and elimination of SPECT 123 123Te, EC compounds from the human body. Stable-labeled molecules often serve as internal I artificial 13.3 h imaging standards in mass spectrometry and NMR studies. Radioactive molecules are also used in imaging and radiation therapy. 131 – radiation 131I artificial Xe, β 8.02 h therapy Radioactive isotopes: 3T, 11C, 14C, 13N, 15O, 18F, 35S, 124I, 131I... Diagnostic medical imaging: 3 main techniques, all using gamma cameras Stable isotopes: 2D, 13C, 15N, 17O, 18O... * Scintigraphy: 2D imaging Isotopomers or isotopic isomers: two molecules with the same number of each isotopic * SPECT (Single-photon emission computed tomography): 3D imaging by reconstitution, directly detects gamma rays atom but differing in their positions, e.g.: * PET (Positron emission tomography): 3D imaging by reconstitution, detects gamma rays produced by annihilation of a positron and an electron 2D 2D 2D Note: Radiography uses electromagnetic radiation (X-rays) and does not require any 2 Me Me Me CH2 D Me OH Me OH radioactive molecules! H O, H 18O, Isotopologues: molecules only differing in their isotopic constitution, e.g.: 2 2 2 D2O... 1 Short Stories in Pharmaceutical Discovery, Q. Michaudel Process and Isotopic Labeling Baran Lab GM 2011-11-19 Production of small radioactive building blocks: Small radioactive molecules (e.g. CO2) are produced in a cyclotron and chemically transformed. Enzymatic transformations have also been developed. For example for 11C labeling: 11 CH3SH CuSO4 Na2S2O5 R3P 11 CH3IH H Pt, NH3 I2 n–BuLi N 11 H11CN 11CH 11CH I 11CH Li Cu CN Br3 4 3 3 11 AgNO2 CNBr 11 11 Cl2 CH3NO2 Fe/O2 CCl4 Ni, H HI 2 Fe–Mo LiAlH PtCl4 Zn 4 cat 11 11 11 11 11 SPECT scanner COCl2 CO CO2 CH3OH H CHO source: UCAIR website MeLi K, http://www.ucair.med.utah.edu/ NH3 NH What_is_SPECT.html 3 11 11 11 Me2 CO R CH2OH R CHO 11 11 CO(NH2)2 K CN Common radiopharmaceuticals 11 for 18F PET: R CH2NO2 HO Handbook of radiopharmaceuticals : radiochemistry and R11CH I R11CH Li applications / editors, Michael J. Welch, Carol S. Redvanly 3 2 Published !Chichester, England ; Hoboken, NJ : Wiley, HO 18F c2003 11 R CH3SH CO H 2 Stable isotope natural abundance: 2D : 0.0156% 13 NH 2 CH3OH (99%): $167.00/1g 2 13 13 2 2 C: 1.1% C D3O D (99%, 99.5%): $277.50/1g 15N: 0.00364% 13 18F-Fluoro-Dopa CH2O (99%): $368.50/1g 18 13 O: 0.00205% H CO2H (99%): $363.50/1g 17 13 O: 0.00038% COCl2 (99%, 1M in benzene): $396.50/5mL Price examples of stable-labeled OMe N building blocks (Sigma-Aldrich): 15 N NH3 (98%): $432.00/1L 2D O (99.994%): $12.40/1g N N O 2 2 18 C D3OH (99.8%): $39.90/1g H2 O (99%): $992.00/1g 18F PET principle 2 2 2 18 C D3O D (99.96%): $48.30/1g D2 O (95%): $839.00/1g 2 2 18 C D O in D O (98%): $19.83/1g CH3 OH (95%): $993.00/1g source Dr. Bernard Langlois Fluorine Chemistry 2 2 MPPF 2DCO 2D in 2D O (99%): $42.00/1g class 2 2 18F 2 17 C6 D6 (99.96%): $18.58/1g CH3 OH (20%): $1,290.00/1g!!! 2 Short Stories in Pharmaceutical Discovery, Q. Michaudel Process and Isotopic Labeling Baran Lab GM 2011-11-19 OH Me Synthesis of small labeled molecules: O 17 17 2 H2 O H2 O Activity (A) = # decays per seconde N A(final product) Radiochemical yield (RY): RY = x100 OH Me 17O A(starting material) 17 O2 Specific activity (SA): activity for one mole. Unit = Ci/mol with Ci = 3.7x1010 Bq = 37 GBq O Me O 13 BH3 NH3 + H 17O B 2 H2 2 2 13 NH2 3 8 THF 8 3 NaOCl 8 N Appl. Radiat. Isot. 43, 389 O Me J. Label. Compd. Radiopharm. 2010, 53, 78 13 NH3 AgNO3 NaCl 13 13 2+ 13 K2PtI4 ( NH3)2PtI2 ( NH3)2Pt(H2O)2 ( NH3)2PtCl2 HCl gas 18 18O Cisplatin, RY: 27% H2 O O O J. Label. Compd. J. Nucl. Med. 27, 399 Me Me Radiopharm. 1995 26, 1077 80°C, 87% Me H Me NH2 R1 11C 1. Me2NH2ClO4 Br OH 3T OH J. Label. Compd. Radiopharm. N O H H 11 1999, 36, 33 HO N Me HO N Me 2. CH3NO2, 3 R1 1. T2, Pd/C tBuOK R2 EtOH R2 3. Na2S Br Br 3T 3T Zincke aldehyde 2. HCl OH OH 18 OMe OMe K F, [3T](R,R)–4–methoxyfenoterol OAc Kryptofix OAc OH J. Label. Compd. Radiopharm. 2010, 53, 68 OTf 2.2.2, HCl O O O Cl Cl OAc OAc AcO AcO HO 125 MeCN, 80°C, 55% H2N OH chloramine-T I H2N OH AcO AcO 18 (2 steps) HO 18 OH 125 5 min F F Na I N O N O J. Nucl. Med. 27, 235 2–deoxy–2–[18F]Fluoro–D–glucose prepared in ca. 50min EtOH, pH = 7 18FDP is commonly used for PET [125I]Melphalan J. Label. Compd. Radiopharm. 2010, 53, 68 N O O Cl Cl OH 3T , Pd/C 3T 3T O 2 6N HCl OH NH CO2H 14 N N ClH3N BrCH2CO2Me, CH3I EtOH 3T 3T NNa O CH3ONa NH 2–aminopyridine O O S S N Named reaction? 14 J. Label. Compd. Radiopharm. O O S CH3 O O 14 2008, 51, 113 J. Med. Chem. 1999, 42, 5235 [ C]Piroxicam O O 3 Short Stories in Pharmaceutical Discovery, Q. Michaudel Process and Isotopic Labeling Baran Lab GM 2011-11-19 Temozolomide (Temodar, Merck): O O O 3. 2-mercaptopyridine- N-oxide, * anticancer drug (astrocytoma (brain tumor) and melanoma) Et3N, –15°C O O N N Temozolomide * prodrug, DNA methylating agent N N 4. Bu3SnH, AIBN N (cat), DMF, hν, rt O 21% (4 steps) Discovery route: J. Med. Chem. 1984, 27, 196 NH2 Me O N N N Process route: JCS Chem. Commun. 1994,1687 N Isotopic labeling route (2002): 11C N Isotopic labeling route: J. Med. Chem. 2002, 45, 5448 NH2 O O O all three papers are from Malcolm F. G. Stevens O Cl Me H 11C N N 3 1. Cl O N N N N Discovery route (1984): N N N 11 N 2. CH3I NH 1. dry HCl 2 NH2 O O EtOH:Et2O CO2Et > 0°C, 24h H2N CONH2 PhN2Cl H2N CONH2 O NC H2N 2. sat. NH3 H O, pH = 4 2 H2NOC N2 H2NOC HN N 11 N EtOH, rt, 5d HN HCl rt, 90% HN N N MeNH2 COCl2 HCl N 60% (2 steps) Ph N N 55% N N N NH N NH 11 JACS, 1945 67, 1017 HCOOH, C Me Pd/C 30%, H2, J. Biol. Chem. 1949, 181, 89 O H2O:2-Methoxyethanol JOC 1959, 24, 256 11 11 rt, P > 1 atm, 3-4h COCl2 + MeN(SiMe3)2 –> MeN CO + 2 MeSiCl or 11 11 TL, 1979, 4253 then HCl reflux 15min, 71% COCl2 + MeNSO –> MeN CO + SOCl2 O and 1. aq NaNO 11 11 2 CH3I + AgOCN –> CH3NCO + AgI Me 1N HCl, H2N CONH2 O radiosynthesis N N 0°C, 70% 11 time: ~47 min N H3 C N N N -1 Temozolomide 2. Methyl HN NHCl SA = 64 GBq.µmol N isocyanate N DCM, dark, rt, NCO N NH2 11 CH3 N O 98% Mechanism? NH2 H2NOC N2 O Process route (1984): avoiding the use of Methyl isocyanate (Bhopal disaster, 1984) O O N NH H2N H2N CONH2 1. EtO CCH NCO N 2 2 EtO2C N N MeN DMSO, pyr, 20°C 1. 5N HCl, 45°C 11 N N CO N radiosynthesis N N N time: ~50 min HN NHCl N 11 2. aq NaNO2 2. Me CHCH OCOCl, C Me 2N HCl, 0°C 2 2 SA = 52 NH2 NMO, DMF, –15°C O -1 72% (2 steps) O GBq.µmol 4 Short Stories in Pharmaceutical Discovery, Q. Michaudel Process and Isotopic Labeling Baran Lab GM 2011-11-19 Brivanid (under evaluation, BMS): 13 13 13 O EtO2 C CH3 H3 C 13 1. NaH, NH2Cl, * anticancer C13C 13 * VEGFR-2 kinase inhibitor (tyrosine kinase vascular endothelial growth factor DMF, 0°C, 55% C 15NH 13 13 receptor-2): slow down angiogenesis and tumor progression CO15NH EtO2 C C 30% 15N 2 2.
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