3.1. Chemistry
The chemicals and reagents were purchased from Acros (Shanghai, China), Alfa Aesar (Shanghai, China), and National Chemical Reagent Group Co. Ltd., P. R. China (Shanghai, China), and used without further purification. Anhydrous solvents (THF, MeOH, DMF, CH
2Cl
2 and CH
3CN) used in the reactions were dried and freshly distilled before use. All the reactions were carried out under Ar atmosphere, otherwise stated else. The progress of the reactions was monitored by TLC (silica-coated glass plates) and visualized under UV light, and by using iodine or phosphomolybdic acid. Melting points were measured on an SGW X-4 microscopy melting point apparatus without correction.
1H NMR and
13C NMR spectra were recorded either on a 400 MHz Varian Instrument at 25 °C or 600 MHz Bruker Instrument at 25 °C, using TMS as an internal standard, respectively. Multiplicity is tabulated as s for singlet, d for doublet, dd for doublet of doublet, t for triplet, and m for multiplet. The original spectra of the relative compounds could be found in
Supplementary Materials. HRMS spectra were recorded on Finnigan-Mat-95 mass spectrometer, equipped with ESI source. Largazole, its free thiol and key intermediates (compound
8 and
11) were prepared according to our previous method [
22,
23,
24].
3.1.1. 2-(Trimethylsilyl)ethyl (S,Z)-4-fluoro-3-hydroxy-7-(tritylthio)hept-4-enoate (9)
To a solution of 8 (0.595 g, 0.95 mmoL, 1.0 equiv.) and DMAP (0.183 g, 1.5 mmoL, 1.5 equiv.) in CH2Cl2 (DCM, 20 mL), Me3CH2CH2OH was added (1.36 mL, 9.5 mmol, 10 equiv.), and the resulting solution was stirred at room temperature (rt) overnight. Concentration in vacuo left the residue, which was purified by column chromatography, giving compound 9 (0.341 mg) with a 67% yield as colorless oil. Rf = 0.17 [petroleum ether (PE)/ethyl acetate (EA) 10/1]. 1H-NMR (600 MHz, CDCl3): δ 7.50–7.13 (m, 15H, ArH), 4.81 (dt, J = 37.2, 7.2 Hz, 1H, CH=CF), 4.46 (m, 1H, CHOH), 4.20 (m, 2H, OCH2CH2TMS), 3.14 (brs, 1H, OH), 2.63 (dd, J = 16.2, 3.6 Hz, 1H, CH2CO), 2.58 (dd, J = 16.2, 9.0 Hz, 1H, CH2CO), 2.20 (t, J = 7.2 Hz, 2H, SCH2CH2), 2.14 (t, J = 7.2 Hz, 2H, SCH2CH2), 0.99 (t, J = 8.4 Hz, 2H, OCH2CH2TMS), 0.03 (s, 9H, SiMe3). 13C-NMR (150 MHz, CDCl3): δ 171.4, 157.9 (d, J = 255 Hz), 144.2, 128.9, 127.2, 126.0, 104.2, 66.1 (d, J = 27 Hz), 62.7, 37.9, 30.8, 22.0, 16.6, 2.1. 19F NMR (376 MHz, CDCl3): δ −123.24 (dd, J = 37.6, 11.2 Hz). ESI (m/z): [M + H]+ 537.4.
3.1.2. 2-(Trimethylsilyl)ethyl (S,Z)-3-((N-(((9H-fluoren-9-yl)methoxy)carbonyl)-S-methyl-l-cysteinyl)oxy)-4-fluoro-7-(tritylthio)hept-4-enoate (10c)
To a solution of 9 (0.690 g, 1.28 mmol, 1.0 equiv.) in DCM (10 mL) a solution of S-Me Fmoc-l-Cysteine was added (2.38 g, 6.42 mmol, 5.0 equiv.); DMAP (0.016 g, 0.128 mmol, 0.1 equiv.) and EDCI (1.48 g, 7.7 mmol, 6.0 equiv.) was added in DCM (20 mL) at rt, and DIPEA (1.30 mL, 7.7 mmol, 2.5 equiv.) was added to the stirring solution. The reaction was stirred for 18 h. This solution was quenched with a NH4Cl aqueous solution and separated. The aqueous phase was extracted with DCM (30 mL × 3) and the combined organic phase was washed with H2O, brine, dried with Na2SO4 and filtered. After the removal of the solvent, the resulting crude was purified by flash chromatography on silica gel, eluting with PE/EA (5/1) to afford 10c (0.856 g, 75%) as a white foamy solid. Rf = 0.20 (PE/EA 5/1). 1H-NMR (600 MHz, CDCl3): δ 7.80–7.10 (m, 23H, ArH), 6.64 (m, 1H, CHOC=O), 5.37 (d, J = 8.4 Hz, 1H, NH), 4.88 (dt, J = 36, 7.2 Hz, 1H, CH=CF), 4.49 (m, 1H, CHCH2SMe), 4.40 (m, 2H, OCH2CH[Fmoc]), 4.21 (m, 1H, OCH2CH[Fmoc]), 4.16 (m, 2H, OCH2CH2TMS), 2.80 (dd, J = 16.8, 8.4 Hz, 1H, CH2CO), 2.68 (dd, J = 16.8, 4.8 Hz, 1H, CH2CO), 2.42 (m, 1H, CHCH2SMe), 2.20–2.14 (m, 4H, SCH2CH2), 2.03 (s, 3H, CHCH2SMe), 1.91 (m, CHCH2SMe), 0.96 (t, J = 8.4 Hz, 2H, OCH2CH2TMS), 0.01 (s, 9H, SiMe3). 13C-NMR (150 MHz, CDCl3): δ 170.2, 168.4, 155.1, 153.9 (d, J = 257 Hz), 144.1, 143.2, 143.0, 140.7, 128.9, 127.2, 127.1, 126.4, 126.0, 124.4, 119.3, 108.8 (d, J = 14 Hz), 68.8 (d, J = 29 Hz), 66.4, 66.2, 62.8, 52.4, 46.5, 35.6, 31.2, 30.4, 22.2, 16.6, 14.7, −2.1. 19F NMR (376 MHz, CDCl3): δ −123.28 (dd, J = 37.6, 18.8 Hz). HRMS-ESI (m/z): [M + H]+ calcd. for C50H54FNO6S2SiH: 876.3219, found: 876.3223.
3.1.3. 2-(Trimethylsilyl)ethyl (S,Z)-3-((N-((R)-2′-(((tert-butoxycarbonyl)amino)methyl)-4-methyl-4,5-dihydro-[2,4′-bithiazole]-4-carbonyl)-S-methyl-L-cysteinyl)oxy)-4-fluoro-7-(tritylthio)hept-4-enoate (12c)
To a solution of 10c (0.890 g, 0.90 mmol, 1.0 equiv.) in DCM (60 mL) was added Et2NH (4.74 mL, 29 mmol, 10 equiv.) was added at rt. After stirring for 2 h and removal of the solvent, the residue was purified by flash chromatography on silica gel, eluting with PE/EA (3/2) to afford the corresponding amine (0.465 g, 77%) as a white foamy solid.
A mixture of compound 11 (0.196 g, 0.55 mmol, 1.0 equiv.), the amine (0.438 g, 0.66 mmol, 1.2 equiv.), HOBT (0.089 g, 0.66 mmol, 1.2 equiv.) and EDCI (0.126 g, 0.66 mmol, 1.2 equiv.) was dissolved in dry DCM (50 ml) and stirred at rt for 3 h. The solution was concentrated under reduced pressure, and diluted with EA (150 mL), washed saturated NaHCO3 aqueous solution and brine successively, dried over Na2SO4 and filtered. After removal of the solvent, the residue was purified by flash chromatography on silica gel, eluting with PE/EA (5/2) to afford 12c (84% based on 10c) as a white foamy solid. Rf = 0.30 (PE/EA 5/2). 1H-NMR (600 MHz, CDCl3): δ 7.87 (s, 1H, ArH), 7.5–7.10 (m, 17H, ArH, 2NH), 5.60 (ddd, J = 19.8, 8.4, 5.4 Hz, 1H, CHOC=O), 5.29 (dd, J = 36, 7.2 Hz, 1H, CH=CF), 4.68 (m,1H, CHCH2SMe), 4.62 (d, J = 5.4 Hz, 2H, CH2NHCOCMe3), 4.18 (m, 2H, OCH2CH2SiMe3), 4.04 (d, J = 11.4 Hz, 1H, CqCH2S), 3.32 (d, J = 11.4 Hz, 1H, CqCH2S), 2.81 (dd, J = 16, 8.4 Hz, 1H, CH2CO2), 2.70 (dd, J = 16, 8.4 Hz, 1H, CH2CO2), 2.39 (m, 2H, CHCH2SMe), 2.20–2.00 (m, 4H, Ph3CSCH2CH2), 1.96 (s, 3H, CHCH2SMe), 1.57 (s, 3H, CqCH3), 1.46 (s, 9H, CH2NHCOCMe3), 0.97 (t, J = 8.4 Hz, 3H, OCH2CH2SiMe3), 0.03 (s, 9H, OCH2CH2SiMe3). 13C-NMR (150 MHz, CHCl3): δ 173.6, 168.9, 168.7, 167.8, 164.5, 155.2 (d, 1JC-F = 256 Hz), 147.4, 129.5, 127.9, 126.6, 124.3, 109.2 (d, 2JC-F = 12.4 Hz), 84.3, 69.9 (d, 3JC-F = 29.6 Hz), 57.5, 43.3, 41.1, 38.6, 37.4, 34.2, 31.1, 29.7, 24.1, 22.8, 18.8, 16.5, 14.2. 19F NMR (376 MHz, CDCl3): δ -124.91 (dd, J = 37.6, 18.8 Hz). ESI (m/z): [M + Na]+ 1015.4.
3.1.4. 2-(Trimethylsilyl)ethyl (S,Z)-3-((((R)-2′-(((tert-butoxycarbonyl)amino)methyl)-4-methyl-4,5-dihydro-[2,4′-bithiazole]-4-carbonyl)glycyl)oxy)-4-fluoro-7-(tritylthio)hept-4-enoate (12d)
Compound 12d was prepared from Fmoc-Glycine in 41% yield based on 9 using the same procedure for 12c. 1H NMR (600 MHz, CDCl3) δ 7.85 (s, 1H, ArH), 7.53–7.09 (m, 16H, ArH, NH), 5.68 (ddd, J = 19.7, 8.8, 5.2 Hz, 1H, CHOC=O), 5.36 (brs, 1H, NH), 4.88 (dt, J = 36.0, 8.0 Hz, 1H, CH=CF), 4.61 (d, J = 6.3 Hz, 2H, CH2NHCOCMe3), 4.25–4.08 (m, 2H, OCH2CH2SiMe3), 4.12–3.94 (m, 2H, NHCH2CO2), 3.74 (d, J = 11.7 Hz, 1H, CqCH2S), 3.32 (d, J = 11.5 Hz, 1H, CqCH2S), 2.77 (dd, J = 16.6, 8.7 Hz, 1H, CH2CO2), 2.66 (dd, J = 16.5, 5.0 Hz, 1H, CH2CO2), 2.12 (dd, J = 25.5, 7.1 Hz, 4H, Ph3CSCH2CH2), 1.58 (s, 3H, CqCH3), 1.46 (s, 9H, CH2NHCOCMe3), 1.04–0.88 (m, 2H, OCH2CH2SiMe3), 0.02 (s, 9H, OCH2CH2SiMe3). 13C NMR (150 MHz, CDCl3) δ 174.7, 169.7, 169.1, 168.2, 163.3, 155.6, 154.5 (d, J = 258.2 Hz), 148.5, 144.7, 129.5, 127.8, 126.6, 121.9, 108.9 (d, J = 13.7 Hz), 84.9, 80.4, 69.1 (d, J = 30.2 Hz), 66.6, 63.4, 42.3, 41.2, 41.0, 36.3, 31.0, 28.3, 24.7, 22.8, 17.2, -1.5. 19F NMR (376 MHz, CDCl3): 124.96 (m). ESI (m/z): [M + Na]+ 955.5.
3.1.5. (12Z,22Z,24R,5R,8S)-8-((Z)-1-fluoro-4-(tritylthio)but-1-en-1-yl)-24-methyl-5-((methylthio)methyl)-24,25-dihydro-7-oxa-4,11-diaza-1(4,2),2(2,4)-dithiazolacyclododecaphane-3,6,10-trione (14c)
12c (0.446 g, 0.44 mmol, 1.0 equiv.) was dissolved in a solution of CF3CO2H (5 mL) and dry DCM (20 mL), and stirred at rt overnight. After removal of the solvent under reduced pressure, and the crude amino acid (about 0.408 g) was directly used for the next step.
The amine acid was dissolved in anhydrous DMF (40 mL) and then DIEPA (0.50 mL, 2.66 mmol, 6.0 equiv.) was added to the solution at rt in order to prepare the amine solution. Next, the amine solution was added dropwise to a stirring solution of HATU (0.337 g, 0.89 mmol, 2.0 equiv.) and HOBT (0.120 g, 0.89 mmol, 2.0 equiv.) in anhydrous DMF (80 mL) at rt over 3 h. The resulting solution continued to stir at rt overnight. The mixture was diluted with water (150 mL), and extracted with MeOBut (80 mL). The combined organic phase was washed with a saturated NaHCO3 aqueous solution (50 mL × 3), water (50 mL) and brine (50 mL). After drying by NaSO4, filtration and evaporation, the residue was purified by flash chromatography on silica gel, eluting with PE/EA (1/1) to afford 14c (48% in 2 steps) as a white foamy solid. Rf = 0.20 (PE/EA 1/1). 1H-NMR (600 MHz, CDCl3): δ 7.75 (s, 1H, ArH), 7.5–7.10 (m, 16H, ArH, NH), 6.39 (m, 1H, NH), 5.70 (m, 1H, CHOC=O), 5.52 (dd, J = 17.4, 9.6 Hz, 1H, ArCH2NH), 4.96 (dd, J = 36, 7.2 Hz, 1H, CH=CF), 4.68 (dd, J = 12, 4.2 Hz, 1H, CHCH2SMe), 4.22 (dd, J = 17.4, 3.0 Hz, 1H, ArCH2NH), 4.08 (d, J = 11.4 Hz, 1H, CqCH2S), 3.20 (d, J = 11.4 Hz, 1H, CqCH2S), 3.13 (dd, J = 16, 11.4 Hz, 1H, CH2CO2), 2.70 (d, J = 16, 1H, CH2CO2), 2.30–1.90 (m, 6H, Ph3CSCH2CH2, CHCH2SMe), 1.96 (s, 3H, CHCH2SMe), 1.70 (s, 3H, CqCH3). 13C-NMR (150 MHz, CHCl3): δ 172.8, 168.3, 168.2, 167.2, 163.6, 154.1 (d, 1JC-F = 256 Hz), 146.8, 144.1, 128.9, 127.2, 126.0, 123.8, 108.8 (d, 2JC-F = 12 Hz), 83.6, 69.4 (d, 3JC-F = 30 Hz), 66.0, 51.8, 42.2, 40.6, 36.5, 30.9, 30.4, 27.8, 23.6, 22.2, 14.2. 19F NMR (376 MHz, CDCl3): δ −125.10 (dd, J = 37.6, 18.8 Hz). HRMS-ESI (m/z): [M + H]+ calcd. for C39H39FN4O4S4H: 775.1911, found: 775.1918.
3.1.6. (12Z,22Z,24R,8S)-8-((Z)-1-fluoro-4-(tritylthio)but-1-en-1-yl)-24-methyl-24,25-dihydro-7-oxa-4,11-diaza-1(4,2),2(2,4)-dithiazolacyclododecaphane-3,6,10-trione (14d)
Compound 12d was prepared in 40% yield using the same procedure for 12c. 1H NMR (600 MHz, CDCl3) δ 7.72 (s, 1H, ArH), 7.44–7.17 (m, 15H, ArH), 7.03 (brs, 1H, NH), 6.55–6.46 (m, 1H, NH), 5.76 (dd, J = 22.6, 11.1 Hz, 1H, CHOC=O), 5.19 (dd, J = 17.4, 8.9 Hz, 1H, ArCH2NH), 4.94 (dt, J = 36.0, 8.0 Hz, 1H, CH=CF), 4.24 (dd, J = 17.4, 4.0 Hz, 1H, ArCH2NH), 4.13 (m, 1H, CH2CO2), 4.12 (d, J = 12.0 Hz, 1H, CqCH2S), 3.88 (dd, J = 18.7, 4.0 Hz, 1H, CH2CO2), 3.22 (d, J = 12.0 Hz, 1H, CH2CO2), 3.13 (dd, J = 16.9, 11.3 Hz, 1H, CH2CONH), 2.70 (d, J = 16.8 Hz, 1H, CH2CONH), 2.16–2.14 (m, 4H, Ph3CSCH2CH2), 1.82 (s, 3H, CqCH3). 13C NMR (150 MHz, CDCl3) δ 173.8, 169.0, 167.5, 165.9, 163.7, 154.7 (d, J = 258.2 Hz), 147.4, 144.7, 129.5, 127.8, 126.6, 124.6, 109.6 (t, J = 12.1 Hz), 84.3, 70.0 (d, J = 28.7 Hz), 66.6, 43.6, 42.0, 41.4, 37.1, 31.0, 25.2, 22.8. 19F NMR (376 MHz, CDCl3): δ −129.82 (dd, J = 37.6, 22.5 Hz). HRMS-ESI (m/z): [M + Na]+ calcd. for C37H35FN4O4S3Na: 737.1697, found: 737.1675.
3.1.7. (12Z,22Z,24R,8S)-8-((Z)-1-fluoro-4-mercaptobut-1-en-1-yl)-24-methyl-5-((methylthio)methyl)-24,25-dihydro-7-oxa-4,11-diaza-1(4,2),2(2,4)-dithiazolacyclododecaphane-3,6,10-trione (15c)
14c (0.050 mg, 0.63 mmol, 1.0 equiv.) was dissolved in dry DCM (10 mL) and cooled to 0 °C. The mixture was successively treated with i-Pr3SiH (26 µL, 0.13 mmol, 2.0 equiv.) and TFA (0.30 mL, 4.0 mmol, 6.7 equiv.). The reaction mixture was allowed to warm to rt and stirred for 1.5 h. The reaction was quenched with a saturated NaHCO3 solution (10 mL) and separated. The aqueous phase was extracted with DCM (10 mL × 3), and the combined layers was washed with brine, dried over Na2SO4 and filtered. After removal of the solvent, the residue was purified by flash chromatography on silica gel, eluting with DCM/MeOH (60/1) to afford 15c in 91% yield as a white foamy solid. Rf = 0.30 (PE/EA 2/3). 1H-NMR (400 MHz, CDCl3): δ 1H-NMR (600 MHz, CDCl3): δ 7.78 (s, 1H, ArH), 7.26 (d, J = 7.6 Hz, 1H, NH), 6.44 (dd, J = 10, 3.6 Hz, 1H, NH), 5.77 (ddd, J = 21.2, 11.2, 2.0 Hz, 1H, CHOC=O), 5.28 (dd, J = 17.6, 9.6 Hz, 1H, ArCH2NH), 5.11 (dt, J = 36, 7.6 Hz, 1H, CH=CF), 4.70 (m, 1H, CHCH2SMe), 4.27 (dd, J = 17.6, 3.6 Hz, 1H, ArCH2NH), 4.08 (d, J = 11.2 Hz, 1H, CqCH2S), 3.25 (d, J = 11.2 Hz, 1H, CqCH2S), 3.19 (dd, J = 16.8, 11.2 Hz, 1H, CH2CONH), 2.76 (dd, J = 16.8, 2.4 Hz, 1H, CH2CONH), 2.41 (m, 2H, CH2CH=CF), 2.30–1.90 (m, 4H, CH2SH, CHCH2SMe), 1.87 (s, 3H, CHCH2SMe), 1.85 (s, 3H, CqCH3). 13C-NMR (150 MHz, CHCl3): δ 174.1, 169.5, 169.4, 164.8, 155.9 (d, 1JC-F = 256 Hz), 147.9, 125.0, 109.3 (d, 2JC-F = 12 Hz), 84.8, 70.9 (d, 3JC-F = 30 Hz), 53.0, 43.4, 41.8, 37.8, 28.4, 24.8, 24.3, 15.6. 19F NMR (376 MHz, CDCl3): δ −124.79 (dd, J = 37.6, 18 Hz). HRMS-ESI (m/z): [M + H]+ calcd. for C20H25FN4O4S4H: 533.0815, found: 533.0819.
3.1.8. S-((Z)-4-fluoro-4-((12Z,22Z,24R,5R,8S)-24-methyl-5-((methylthio)methyl)-3,6,10-trioxo-24,25-dihydro-7-oxa-4,11-diaza-1(4,2),2(2,4)-dithiazolacyclododecaphane-8-yl)but-3-en-1-yl) octanethioate (16c)
The free thiol 15c (32 mg, 0.05mmol, equiv.) was dissolved in dry DCM (10 mL) and cooled to 0 °C. The mixture was successively treated with pyridine (23 µL, 0.29 mmol, 5.0 equiv.) and octanoyl chloride (29 µL, 0.17 mmol, 3.0 equiv.). The reaction was allowed to warm to rt and stirred for 2 h, and then quenched with a saturated NaHCO3 solution (10 mL) and separated. The aqueous phase was extracted with DCM (10 mL × 3), and the combined layers was washed with brine, dried over Na2SO4 and filtered. After removal of the solvent, the residue was purified by flash chromatography on silica gel, eluting with DCM/EA (1/1) to afford 16c (57%) as a white foamy solid. Rf = 0.42 (DCM/EA 3/1). 26.4 (c 0.34, CHCl3). 1H-NMR (600 MHz, CDCl3): δ 7.78 (s, 1H, ArH), 7.24 (d, J = 11.4 Hz, 1H, NH), 6.54 (dd, J = 9.6, 3.6 Hz, 1H, NH), 5.76 (ddd, J = 21, 11.4, 2.4 Hz, 1H, CHOC=O), 5.30 (dd, J = 17.4, 9.6 Hz, 1H, ArCH2NH), 5.09 (dt, J = 36, 7.2 Hz, 1H, CH=CF), 4.71 (m, 1H, CHCH2SMe), 4.27 (dd, J = 17.5, 3.0 Hz, 1H, ArCH2NH), 4.10 (d, J = 11.4 Hz, 1H, CqCH2S), 3.28 (d, J = 11.4 Hz, 1H, CqCH2S), 3.19 (dd, J = 16.8, 11.4 Hz, 1H, CH2CONH), 2.90 (t, J = 7.2 Hz, 2H, SCH2CH2), 2.75 (dd, J = 16.8, 2.4 Hz, 1H, CH2CONH), 2.54 (t, J = 7.5 Hz, 2H, CH2COS), 2.40–2.30 (m, 2H, SCH2CH2), 2.30–1.90 (m, 2H, CHCH2SMe), 1.87 (s, 3H, CHCH2SMe), 1.86 (s, 3H, CqCH3), 1.70–1.6 (m, 2H, CH2), 1.40–1.10 (m, 8H, CH2), 0.89 (t, J = 6.0 Hz, 3H, CH3CH2). 13C-NMR (150 MHz, CDCl3): δ 198.6, 172.9, 168.3, 168.2, 167.3, 163.8, 154.7 (d, J = 256 Hz), 146.7, 123.9, 108.1 (d, J = 12 Hz), 83.6, 69. 5 (d, J = 30 Hz), 51.8, 43.5, 42.2, 40.6, 36.5, 30.9, 28.4, 27.2, 24.9, 24.1, 23. 6, 23.2, 21.9, 14.4, 13.4. 19F NMR (376 MHz, CDCl3): δ −124.69 (dd, J = 35.9, 20.9 Hz). HRMS-ESI (m/z): [M + Na]+ calcd. for C28H39FN4O5S4Na: 681.1680, found: 681.1693.
3.1.9. S-((Z)-4-fluoro-4-((12Z,22Z,24R,8S)-24-methyl-3,6,10-trioxo-24,25-dihydro-7-oxa-4,11-diaza-1(4,2),2(2,4)-dithiazolacyclododecaphane-8-yl)but-3-en-1-yl) octanethioate (16d)
Compound 16d was prepared in 40% yield from 14d using the same procedure for 16c. 37.9 (c 0.14, CHCl3). 1H NMR (600 MHz, CDCl3) δ 7.71 (s, 1H, ArH), 7.00 (m, 1H, NH), 6.60 (dd, J = 9.1, 4.1 Hz, 1H, NH), 5.78 (dd, J = 22.3, 11.1 Hz, 1H, CHOC=O), 5.18 (dd, J = 17.4, 8.8 Hz, 1H, ArCH2NH), 5.04 (dt, J = 36.1, 7.5 Hz, 1H, CH=CF), 4.24 (dd, J = 17.5, 4.0 Hz, 1H, ArCH2NH), 4.15 (m, 1H, CH2CO2), 4.10 (d, J = 11.7 Hz, 1H, CqCH2S), 3.87 (dd, J = 18.9, 3.1 Hz, 1H), 3.20 (d, J = 11.2 Hz, 1H, CqCH2S), 3.14 (dd, J = 16.0, 12.0 Hz, 1H, CH2CONH), 2.86 (t, J = 7.1 Hz, 2H, SCH2CH2), 2.71 (d, J = 16.9 Hz, 1H, CH2CO), 2.50 (t, J = 7.6 Hz, 2H, C6H13CH2CO), 2.41–2.27 (m, 2H, SCH2CH2), 2.11–1.87 (m, 2H), 1.79 (s, 3H, CqCH3), 1.60–1.15 (m, 10H), 0.84 (t, J = 6.6 Hz, 3H, CH3-C5H11-CH2CO). 19F NMR (376 MHz, CDCl3): δ −123.29 (dd, J = 35.9, 20.9 Hz). HRMS-ESI (m/z): [M + Na]+ calcd. for C26H35FN4O5S3Na: 621.1646, found: 621.1650.