135 Entry Pressure
EXPERIMENTAL SECTION
All commercially available reagents were purchased from Acros, Alfa Aesar, Fisher Scientific, Fluorochem or Sigma-Aldrich and used without further purification.
Reactions were performed under an atmosphere of argon using standard vacuum line techniques, unless otherwise stated. All glassware was oven-dried and allowed to cool down under high vacuum. All reactions that involved the use of HF-containing reagents were conducted in teflon round bottom flasks previously oven-dried and allowed to cool under high vacuum. Dry solvents dichloromethane, tetrahydrofuran, methanol were obtained from the MBraun SPS-800 Solvent Purification System, by passing the solvent through two drying columns under an argon atmosphere. Temperature of 0 °C was obtained using an ice/water bath. Reactions requiring heating or reflux were carried out using a heating block with a contact thermometer.
Thin layer chromatography (TLC) was performed using Merck TLC silica gel 60 F254
glass-backed plates. Compounds were visualised by either UV light (254 nm) or by the use of potassium permanganate stain or molybdenum-based stain. Reverse-phase preparative HPLC column chromatography were performed using a Shimadtzu Prominence® HPLC system (either using UV-Vis or diode array detectors), a Waters 600E multisolvent HPLC system coupled to a Waters 2487 dual wavelength absorbance detector or a Waters 2795 HPLC system coupled to a Waters LCT-MS mass detector, and a semipreparative Phenomenex Synergi® 4μ Polar-RP 80Å 250 x 10.0 mm column, eluting with mixtures of acetonitrile and water with or without using trifluoroacetic acid as a modifier. Optical rotations were measured in a 10 cm length cuvette using the Na589nm
on a Perkin Elmer 341 Polarimeter.
NMR spectra were recorded on Bruker Avance II 400 spectrometers (1H at 400 MHz, 13C
at 100 MHz, 19F at 376 MHz), or Bruker Avance III 500 spectrometers (1H at 500 MHz, 13C at 126 MHz, 19F at 470 MHz) or Bruker Avance III spectrometer (1H at 700 MHz, 13C
at 175 MHz, 19F at 658 MHz).
Chemical shifts (δ) are reported in parts per million (ppm) and are quoted relative to the residual peak of CDCl3, (CD3)2SO, CD3OD, D2O. Coupling constants (J) are given in
Hertz (Hz). 13C NMR were recorded with 1H decoupling, and 19F NMR spectra were
recorded either with or without 1H decoupling. Signal splitting patterns are described as:
s – singlet, br s – broad singlet, d – doublet, t – triplet, tt – triplet of triplets, m – multiplet. Mass spectrometric data were acquired by electron impact ionisation (EI), electrospray ionisation (ESI), and nano- electrospray ionisation (NSI) or chemical ionisation (CI), using Waters Micromass LCT (ESI) or GCT (CI) spectrometers (University of St
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Andrews), or a Thermofisher LTQ Orbitrap XL spectrometer (APCI) (National Mass Spectrometry Service Centre, Swansea). Values are reported as a ratio of mass to charge (m/z). Melting points were determined in Pyrex capillaries using a Griffin Melting Point Apparatus and are uncorrected.
Enzymatic activity assays were carried out using a Thermo Scientific Evolution 220 UV- Vis spectrophotometer.1
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Compound 294 was synthesised according to the procedure reported by Tosin et al.2
D-Pantothenic acid hemicalcium salt (5.0 g, 21.0 mmol, 14 equiv.) was suspended in acetic anhydride (100 mL), iodine (0.37 g, 1.5 mmol, 1 equiv.) was added and the resulting brown mixture was stirred for 16 hours at room temperature. The resulting gel was broken into pieces using a spatula and cooled down using an ice bath before adding a saturated solution of sodium hydrogen sulfite (50 mL) and water (100 mL). The mixture was strongly stirred for 1 hour and then concentrated under reduced pressure to remove the excess of acetic acid. Dichloromethane (100 mL) was added and the layers were separated. The aqueous layer was extracted with dichloromethane (50 mL), and the combined organic layers were dried onto magnesium sulfate, filtered and concentrated under reduced pressure to give a yellow oil. This material was dissolved in a 3:1 tetrahydrofuran/water mixture (100 mL) and stirred for 16 hours at room temperature. The mixture was then concentrated under reduced pressure. The crude was then dissolved in dichloromethane (100 mL), the layers were separated and the aqueous layer extracted with dichloromethane (50 mL). The combined organic layers were dried onto magnesium sulfate, filtered and concentrated under reduce pressure to afford a clear oil that crystallised into a colourless solid (obtained 4.10 g, 0.97 mmol, 65% yield). Diacetyl pantothenic acid was used either in both forms without affecting the reaction outcome. Mp: 102-104 ºC; [α]20 D = + 11.0 ° (c 0.01, CHCl3) 1H NMR (500 MHz, CDCl 3) δ 6.64 – 6.62 (t, J = 6.10 Hz, 1H, NH,), 4.96 (s, 1H,CH, H6), 4.03 (d, J = 10.9 Hz, 1H,CH2, H8a, H8b), 3.82 (d, J = 10.9, 1H, CH2, H8a, H8b), 3.62 - 3.56 (m, 1H, CH2, H3), 3.52 - 3.46 (m, 1H, CH2, H3), 2.60 (t, J = 5.44, 2H, CH2, H2), 2.14 (s, 3H, CH3, H11), 2.07 (s, 3H, CH3, H14), 1.06 (s, 3H, CH3, H16), 1.03 (s, 3H, CH3, H15).
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D-pantothenic acid diacetate 294 (2.52 g, 8.20 mmol, 1 equiv.) was dissolved in dry tetrahydrofuran (30 mL) under an atmosphere of argon and 1,1-carbonyl diimidazole (1.34 g, 8.20 mmol, 1 equiv.) was added portion wise to the reaction mixture which was then stirred for 2 hours at room temperature. After the production of gas had ceased, cysteamine hydrochloride (0.93 g, 8.20 mmol, 1 equiv.) was added and the resulting mixture was heated under reflux for 6 hours. The mixture was then cooled down to room temperature and concentrated under reduced pressure. The resulting crude was then dissolved in dichloromethane (60 mL). This mixture was then washed with saturated brine (50 mL), 2.0 N hydrochloric acid (50 mL), saturated sodium hydrogen carbonate aqueous solution (50 mL) and saturated brine (50 mL). The residue was dried onto magnesium sulfate, filtered and concentrated under reduced pressure to afford a colourless solid residue which was purified by silica gel flash chromatography eluting with a mixture of 5/95 methanol/dichloromethane, to give the desired compound as a colourless solid (obtained 1.97 g, 5.11 mmol, 66% yield).1
Mp: 58-60 ºC; 1H NMR (500 MHz, CDCl 3) δ 6.96 - 6.93 (t, J = 6.3 Hz, 1H, NH), 6.56 - 6.54 (t, J= 6.5 Hz, 1H, NH), 4.84 (s, 1H, CH, H10), 3.98 (d, J = 11.5 Hz, 1H, CH2, H12a, H12b), 3.79 (d, J = 11.5 Hz, 1H, CH2, H12a, H12b), 3.53 - 3.30 (m, 4H, CH2, H5, H3), 2.67-2.57 (m, 2H, CH2, H2), 2.37 (t, J = 5.66 Hz, 2H, CH2, H6), 2.10 (s, 3H, CH3, H18), 2.02 (s, 3H, CH3, H15), 1.40 (t, J = 8.37 Hz, 1H, SH), 1.01 (s, 3H, CH3, H19), 0.98 (s, 3H, CH3, H20); 13C NMR (126 MHz, CDCl
3) δ 171.8 (COCH3, C17), 171.0 (CONH, C9), 170.3 (COCH3,
C14), 168.2 (CONH, C5), 77.1 (CH, C10), 69.3 (CH2, C12), 42.4 (CH2, C3), 35.3 (CH2,
C6), 35.2 (CH2, C7), 24.5 (CH2, C2), 21.4 (CH3, C18), 21.0 (CH3, C15), 20.9 (CH3, C20),
20.8 (CH3, C19);
m/z (ESI+): Found [M+Na]+ 385.1394. C
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5.4.1. Gold phthalimide complex (Au-1) L= John Phos (286)3
The catalyst was prepared according to the procedure reported by Han et al. 3
Chloro (1,1’-biphenyl-2-yl)-di-tert-butyl phosphine gold (I) (0.30 g, 0.56 mmol, 1 equiv.) and potassium phthalimide (0.16 g, 0.85 mmol, 1.5 equiv.) were dissolved in acetone (6 mL) and the suspension was stirred for 3h at 45 °C. Upon completion, the mixture was filtered and the solid was washed with acetone (10 mL). Acetone was evaporated under pressure and the residue was further washed with water. The catalyst was obtained as a white solid (obtained 0.12 g, 0.19 mmol, 99 % yield).
1H NMR (500 MHz, CDCl 3) δ 7.89 (td, 1H, J = 8.0 Hz, 1H, CH, H10 ), 7.67 (dd, J = 5.3, 3.0 Hz, 2H, CHaryl, H3, H16), 7.57 (dd, J = 5.4, 3.0 Hz, 2H, CHaryl, H4, H5), 7.54 – 7.46 (m, 2H, CH2, H11, H21), 7.32 – 7.27 (m, 2H, CH2, H12, H20), 7.19 – 7.12 (m, 2H, CH2, H15, H19), 6.87 (t, J = 7.7 Hz, 2H, CH2, H16, H18), 1.48 (s, 9H, CH3, H9), 1.45 (s, 9H, CH3, H9’). 13C NMR (126 MHz, CDCl 3) δ 177.9, 150.2 (d, J = 6 Hz, C=O), 142.4 (d, J = 6 Hz, Cquaternary), 136.7 (d, J = 3 Hz, CH, C3 ), 133.6 (d, J = 3 Hz, CH, C4), 132.9 (d, J = 6 Hz, CH, C5), 132.0, 130.4 (d, J = 2 Hz, CHAryl), 128.9, 128.4, 126.9, 126.6 (d = J = 6 Hz, CHAryl), 126.0 (d, J = 45 Hz, CH, C17), 121.4, 37.8 (d, J = 25 Hz, CH, C10), 30.9 (d, J = 6 Hz, CH3, C9 ). 31P NMR (162 MHz, Chloroform-d) δ 58.18.