Academ Present 022009 001[1]

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Academ Present 022009 001[1]

  1. 1. Prolog Overview publications <ul><li>JOURNAL PUBLICATIONS/PATENTS </li></ul><ul><li>Pieter Otten and Benjamin Littler, “Heat Flow Profiling as a Tool to Assess the Scale-up of Biphasic Reaction”, In Progress for Organic Process Research and Development </li></ul><ul><li>“ Fluorescent Magnesium Indicators”, Robert E. London, Pieter A. Otten , and Louis A. Levy. US Patent 6,706,528 </li></ul><ul><li>Yu, J.; Otten, P .; Ma, Z.; Cui, W.; Liu, L.; Mason, R. P., “Novel NMR Platform for Detecting Gene Transfection: Synthesis and Evaluation of Fluorinated Phenyl b-D-Galactosides with Potential Application for Assessing LacZ Gene Expression”. Bioconjugate Chemistry, 15(6); 1334: 2004 </li></ul><ul><li>Weina Cui, Pieter Otten , Yingming Li, Kenneth Koeneman, Jianxin Yu, and Ralph P. Mason, “Novel NMR Approach to Assessing Gene Transfection: 4-Fluoro-2-Nitrophenyl-β-D-Galactopyranoside as a Prototype Reporter Molecule for β-Galactosidase”. Magnetic Resonance in Medicine, 51 (3); 616:2004 </li></ul><ul><li>Pieter A. Otten , Robert E. London, and Louis A. Levy, “4-Oxo-4 H -quinolizine-3-carboxylic Acids as Mg2+ Selective, Fluorescent Indicators”. Bioconjugate Chemistry, 12; 203: 2001 </li></ul><ul><li>Pieter A. Otten , Robert E. London, and Louis A. Levy, “A New Approach to the Synthesis of APTRA Indicators”. Bioconjugate Chemistry, 12; 76: 2001 </li></ul><ul><li>Pieter A. Otten , Syb Gorter, and Arne van der Gen, “A Structural Study of Selenobenzamides. Crystal Structures and Dynamic 13C NMR”. Chem. Ber./Recl. Trav. Chim. Pays-Bas, 130; 49: 1997 </li></ul><ul><li>Pieter A. Otten , Honorine M. Davis, Jan Hein van Steenis, Syb Gorter, and Arne van der Gen, “Stereoselective Synthesis of ( Z )-1-Chlorovinyl Sulfoxides”. Tetrahedron, 53; 10527: 1997 </li></ul><ul><li>Pieter A. Otten , Njord Oskam, and Arne van der Gen, “A Horner-Wittig Approach to S,N -Ketene Acetals. Acid-catalyzed Hydrolysis of S,N -Ketene Acetals to ( S )-Thioesters”. Tetrahedron, 52; 11095: 1996 </li></ul><ul><li>Pieter A. Otten , Honorine M. Davis, and Arne van der Gen, “A Horner-Wittig Synthesis of 1-Chlorovinyl Sulfoxides”. Tetrahedron Letters, 36; 781: 1995 </li></ul><ul><li>Pieter A. Otten and Arne van der Gen, “The Reaction of  -Amino-substituted Diphenyl Phosphine Oxide Anions with Elemental Sulfur and Selenium. A New Route to Thio- and Selenoamides”. Recl. Trav. Chim. Pays-Bas, 113; 499: 1994 </li></ul>
  2. 2. Horner-Wittig Reagents in Sulfur and Selenium Chemistry Pieter Otten and Arne van der Gen Leiden Institute of Chemistry Leiden University, The Netherlands P S Se
  3. 3. Advantages of Diphenylphosphine Oxides <ul><li>Crystalline materials </li></ul><ul><li>Reactive anions </li></ul><ul><li>Superb anion stability </li></ul><ul><li>Excellent stereoselectivity </li></ul><ul><li>Water soluble by-product </li></ul>
  4. 4. Thioamide Synthesis Aminomethylphosphine oxides, excellent reagents for enamine formation, show a unique reactivity towards chalcogens to form amides R = aryl: reaction at r.t R = alkyl: reaction at 0 o C to quell deprotonation of formed thioalkanamides by the HW reagent
  5. 5. Selenoamide Synthesis “ Red selenium”, Se 8 , more reactive than metallic or gray Se; allows isolation of acidic selenoalkanamides at lower temperatures Reaction is sluggish at ambient.
  6. 6. Mechanistic Considerations One eq. of S gives < 50% yield, recover phosphine oxide All intermediates isolated and characterized. Mass balance accounted for. Intermediate trapped at low temperatures with MeI Independently confirmed
  7. 7. Crystal Structure Selenobenzamides Amino group reduces dihedral angle  C=Se: 1.840 Å C-N: 1.331 Å  = 53.3º C=Se: 1.824 Å  = 81.1º C(5) is sp 2 -hydrid.
  8. 8. Other Selenocarbonyls C=Se of selenoamides close to other N- or C=C-conjugated selenocarbonyls
  9. 9. VT 13 C NMR Study: Rotational Barriers C=S and C=Se strongly e-withdrawing groups,  + p fits only More polarizable Se more sensitive to  + p than S o = Se * = S Eyring eq.:  G* rot = 19.5T c x [9.971 + log(T c /  )]
  10. 10. Synthesis of (Thiomethyl)- and (Selenomethyl)phosphine Oxides
  11. 11. Synthesis of Vinyl Selenides <ul><li>>98% E-selectivity if R 1 , R 3 = aryl </li></ul><ul><li>Reacts w/ acidic ketones, HW reagent weakly basic </li></ul><ul><li>E/Z ratio by NMR and GC </li></ul>
  12. 12. Mechanistic Considerations (Curtin-Hammett Principle) Trapped HW-adducts (R3 = Ph -60 o C, H 2 O): R1 = n-Pr: pro(E)/pro(Z) = 1/1, quant. R1 = c-Hex: pro(E)/pro(Z) = 1/1+ 22% (E)-vinyl selenide! Sterics facilitate elimination, k E increases R1 = phenyl, pro(E)/pro(Z) = 3/2. quant, pro-(E) and pro(Z) must rapidly equilibrate via reverse to aldehyde and/or epimerization and (E)-isomer is thermodynamic sink pro-(E) Pro-(Z)
  13. 13. Do HW adducts equilibrate? No vinyl selenide derived from propionaldehyde observed: no equilibration via reverse reaction with aliphatic aldehydes. Cannot rule out epimerization. Fast equilibration with aromatic aldehydes to explain discrepancy between pro-(E) and pro-(Z) ratio for isolated HW adduct (3/2) and strong E-selectivity for completed HW reaction.
  14. 14. Alternate Intermediate Warren proposes this late-stage intermediate to explain high pro-(Z) selectivity for simple alkyl phosphine oxides (R1 = alkyl) Pro-(E) Six-centered transition state. R1 equatorial to avoid 1,3-interaction with equatorial Ph. Low energy difference between SeR3 equatorial or axial, reflected by observed low stereoselectivity In HW-adducts. Pro-(Z)
  15. 15. Formation of 1-Chlorovinyl Sulfoxides A New Class of Compounds (1994)
  16. 16. >96% Z-selectivity if R 2 = aryl, alkenyl and/or R 1 = aryl
  17. 17. Crystal Structure Confirms Z-geometry P -1 , a = 13.3146, b = 11.326, c = 9.395 Å;  = 125.15  = 97.88,  = 96.76; V = 1097.45 Å 3 , Z = 4,  = 1.396 kg/dm 3
  18. 18. Mechanistic Considerations Phosphine oxide anion and carbonyl are in equilibrium w/ adduct. Fast when R1 = anion stabilizing aryl Rotation sets up for the oxaphosphetane. Sterics favor pro-(Z) intermediate Thermodynamic sink Elimination fast if R2 stabilizes double bond: aryl, vinyl
  19. 19. Mechanistic Considerations: Alternate Approach Surprisingly poor stereochemistry with bulky c-hexanecarboxaldehyde Li + ligated between P=O and S=O. R1 equatorial to avoid axial Ph. Aldehyde approaches with R2 pointing away from axial Ph. Must be an intermediate trough on the energy surface
  20. 20. Michael Addition P 2 1 , a = 6.371, b = 7.646, c = 12.364 Å;  = 90.0  = 98.45,  = 90.0; V = 595.7 Å 3 , Z = 2,  = 1.50 kg/dm 3
  21. 21. Mechanistic Considerations A compact sodium complex is formed, dictating stereochemistry Malonitrile gives 1:1 mixture of diastereoisomers
  22. 22. Synthesis of S , N -ketene Acetals and Thioesters R2=aryl: pure ketene acetale after extractive work-up only. R2=alkyl, contaminated w/ condensation products. Carry thru to thioester for good use
  23. 23. Goals Achieved <ul><li>User-friendly access to thio- and selenoamides </li></ul><ul><li>Proved role of substitution on aryl ring in </li></ul><ul><li>conjugation in selenobenzamides </li></ul><ul><li>Stereoselective formation of 1-chlorovinyl sulfoxides </li></ul><ul><li>Demonstrated diastereoselective Michael addition </li></ul><ul><li>on 1-chlorovinyl sulfoxides </li></ul><ul><li>General synthesis of vinyl selenides </li></ul><ul><li>Facile synthesis of S , N -ketene acetals </li></ul><ul><li>Homologation of aldehydes to (S)-thioesters </li></ul>
  24. 24. Fluorescent Magnesium Indicators Pieter Otten, Louis Levy, and Robert London, National Institute of Environmental Health Sciences, RTP, NC
  25. 25. Physiological Importance of Mg 2+ <ul><li>Mg 2+ , most abundant divalent cation: </li></ul><ul><li>300 enzymatic reactions </li></ul><ul><li>Energy production </li></ul><ul><li>Hormone regulation </li></ul><ul><li>DNA synthesis </li></ul><ul><li>Muscle contraction </li></ul><ul><li>Mg-deficiency linked to: </li></ul><ul><li>Atherosclerosis </li></ul><ul><li>Hypertension </li></ul><ul><li>Kidney stones </li></ul><ul><li>Migraines </li></ul><ul><li>Psychiatric problems </li></ul>
  26. 26. Ideal, Fluorescent Mg 2+ Indicator However, fluoresc. behavior of difficult to predict <ul><li>Selective for Mg </li></ul><ul><li>Ratioable </li></ul><ul><li>Polycarboxylate </li></ul><ul><li>Excitation > 340 nm </li></ul><ul><li>Emission > 500 nm </li></ul><ul><li>Photostable </li></ul><ul><li>Non-toxic </li></ul>
  27. 27. Why APTRA (Aminophenol Triacetic Acid)? At physiol. Mg 2+ , BAPTA binds two ions. Cut BAPTA in half to get to APTRA.
  28. 28. Pd coupling: fast, one step approach to quickly invest structural diversity
  29. 29. Suzuki Coupling K D, Mg = 2.3 mM K D, Ca = 70  M K D, Mg = 2.1 mM K D, Ca = 28  M K D, Mg = 1.8 mM K D, Ca = 17  M
  30. 30. Fluorescence Excitation Titration Response to Mg and Ca is not identical, which was often assumed to correct for Ca-spikes
  31. 31. Synthesis of 4-Oxo-4 H -quinolizine-3-carboxylates Known complexers of Mg 2+ to shut down bacterial DNA-gyrase w/ K D = 1 mM Explore reactivity to diversify quickly
  32. 32. Electrophilic Aromatic Substitution
  33. 33. 4-Oxo-4 H -quinolizine-3-carboxylic Acids Compare:
  34. 34. Representative Examples; Tri-acids
  35. 35. Synthesis Bromo-substituted Triacid Introduce 3 rd ester, as decarboxylation could not be prevented
  36. 36. Fluorescence Emission Spectrum The first Mg-selective, ratioable fluorophore!
  37. 37. Selected Fluorophores Emission > 500 nm Ratioable
  38. 38. Suzuki Coupling <ul><li>Poor aq solubility </li></ul><ul><li>Future exploration: </li></ul><ul><li>Buchwald </li></ul><ul><li>Libraries of boronic acids anno 2009 </li></ul>
  39. 39. Goals Achieved: <ul><li>Developed a general synthesis of fluorescent APTRA indicators for intra-cellular Mg 2+ and Ca 2+ </li></ul><ul><li>Showed that their response to Mg 2+ and Ca 2+ are not identical </li></ul><ul><li>Designed, synthesized, and evaluated new, ion-selective ratioable, fluorescent indicators for Mg 2+ based on 4-oxo-4H-quinolizine-3-carboxylic acids </li></ul>
  40. 40. NMR-active, Fluorinated Reporter Molecules Pieter Otten and Ralph P. Mason Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX
  41. 41. 6-FPOL pK a = 8.2
  42. 42. 6-FPAM pK a = 7.05
  43. 43. CF 3 -POL Triple the fluorines, triple the signal Does not penetrate rbc membrane
  44. 44. Fluorinated Gene Reporter Saline at 30 o C (♦) Plasma at 30 o C (□) Plasma at 37 o C (Δ) Top: pH = 4.5; t = 30 o C; β-gal ( Aspergillus Oryzae ) Bottom: pH = 7.3 -> 6.8; t = 37 o C; β-gal ( E. Coli ) pK a = 6.85

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