3.1. Chemistry
The chemicals and reagents were purchased from Acros, Alfa Aesar, and National Chemical Reagent Group Co. Ltd., 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 an ESI source. Experimental procedures for the preparation of compound
10 and Largazole are available in the reported literature [
28].
3-(Tritylthio)propanal (3)
To a solution of triphenylmethyl mercaptan (1.38 g, 5.0 mmol, 1.0 equiv.) in CH2Cl2 (DCM, 30 mL) acrolein (0.393 g, 7.0 mmol, 1.4 equiv.) and triethylamine (0.98 mL, 7.0 mmol, 1.4 equiv.) was added, and the resulting mixture was stirred at room temperature for 1 h. Concentration in vacuo left aldehyde 3 as a white foamy solid. Rf = 0.13 [petroleum ether (PE)/ethyl acetate (EA) 40/1], 1H-NMR (400 MHz, CDCl3): δ 9.56 (brs, 1H), 7.23–7.43 (m, 15H), 2.47 (t, J = 7.0 Hz, 2H), 2.37 (t, J = 6.7 Hz, 2H).
Ethyl 2-fluoro-5-(tritylthio)pent-2-enoate (4)
To an anhydrous THF solution (30 mL) of PPh3 (3.15 g, 12.0 mmol, 4.0 equiv) and ethyl bromodifluoroacetate (0.83 mL, 6.0 mmol, 2.0 equiv), 1.0 M Et2Zn in hexane (12 mL, 12.0 mmol, 4.0 equiv) was rapidly added under argon. The mixture was stirred for 10 min (until the internal temperature returned to rt), then the aldehyde 3 (0.997 g, 3.0 mmol) was rapidly added. The mixture was stirred overnight. The resulting solution was then quenched with EtOH (15 mL), stirred for 15 min, and concentrated under reduced pressure. The residue was taken up in Et2O (100 mL) and filtered through Celite and then it was chromatographed (silica gel, PE/EA 40/1) to afford the ɑ-fluoroacrylate 4, with E-isomer (0.325 g, 26%) and Z-isomer (0.730 g, 58%), respectively, or afford 4 with a mixture of them (Z/E 3/1, determined by 19F NMR) in 97% yield.
For Z-4: Rf = 0.35 (PE/EA 40/1). 1H-NMR (400 MHz, CDCl3): δ 7.40 (m, 6H), 7.25 (m, 6H), 7.18 (m, 3H), 5.75 (dt, J = 20.9, 7.9 Hz, 1H), 4.23 (q, J = 7.1 Hz, 2H), 2.56 (m, 2H), 2.26 (t, J = 7.2 Hz, 2H), 1.29 (t, J = 7.1 Hz, 3H). 13C-NMR (150 MHz, CDCl3): δ 160.58 (d, 2JC-F = 34.5 Hz), 147.91 (d, 1JC-F = 252 Hz), 144.65, 129.48, 127.81, 126.60, 121.24 (d, 2JC-F = 19.6 Hz), 66.71, 61.28, 31.30, 24.55 (d, 3JC-F = 5.1 Hz), 14.00. 19F-NMR (376 MHz, CDCl3): δ –121.29 (d, J = 22.6 Hz). ESI-MS (m/z): 443.6 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C26H25FO2SNa: 443.1452, found: 443.1452.
For E-4: Rf = 0.27 (PE/EA 40/1). 1H-NMR (400 MHz, CDCl3): δ 7.41 (m, 6H), 7.28 (m, 6H), 7.22 (m, 3H), 5.97 (dt, J = 32.8, 7.2 Hz, 1H), 4.25 (q, J = 7.1 Hz, 2H), 2.25 (m, 4H), 1.31 (t, J = 7.1 Hz, 3H). 13C-NMR (150 MHz, CDCl3): δ 155.83 (d, 2JC-F = 34.5 Hz), 143.62 (d, 1JC-F = 256.5 Hz), 139.93, 124.82, 123.19, 121.99, 113.57 (d, 2JC-F = 11.4 Hz), 62.15, 56.85, 25.79, 18.90, 9.39. 19F-NMR (376 MHz, CDCl3): δ –128.95 (d, J = 32.8 Hz). ESI-MS (m/z): 443.6 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C26H25FO2SNa: 443.1452, found: 443.1454.
(Z)-2-Fluoro-5-(tritylthio)pent-2-enal (5)
To an anhydrous toluene solution (100 mL) of a mixture of Z-4 and E-4 prepared above (4.03 g, 9.58 mmol) 1.5 M DIBALH in toluene (22.4 mL, 33.5 mmol) was added dropwise under argon at −78 °C over 0.5 h. The mixture was stirred at −78 °C for 1 h, and the resulting solution was then quenched with MeOH (50 mL), and warmed to rt. After addition of the saturated aqueous solution of Rochelle salt, the mixture was stirred for overnight, and then the organic phase was separated. The aqueous phase was extracted with EA (100 mL × 2), and the combined organic extracts were dried, filtered, and concentrated in vacuo, and then it was chromatographed (silica gel, PE/DCM/EA 35/5/1) to afford the aldehyde 5 as a white foamy solid (3.10 g, 86%). Rf = 0.35 (PE/DCM/EA 35/5/1). 1H-NMR (400 MHz, CDCl3): δ 9.13 (d, J = 18.2 Hz, 1H), 7.43 (m, 6H), 7.27 (m, 9H), 5.75 (dt, J = 32.1, 7.2 Hz, 1H), 2.35 (m, 4H). 13C-NMR (100 MHz, CDCl3): δ 183.49 (d, 2JC-F = 24.9 Hz), 156.48 (d, 1JC-F = 261 Hz), 146.88, 144.53, 129.54, 128.71 (d, 2JC-F = 10.2 Hz), 127.99, 127.92, 127.29, 126.86, 67.09, 30.22, 24.01. 19F-NMR (376 MHz, CDCl3): δ −132.15 (dd, J = 32.1, 18.2 Hz). ESI-MS (m/z): 399.6 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C24H21FOSNa: 399.1189, found: 399.1192.
(S/R,Z)-1-((R)-4-Benzyl-2-thioxothiazolidin-3-yl)-4-fluoro-3-hydroxy-7-(tritylthio)hept-4-en-1-one (8/9)
6 (1.12 g, 4.46 mmol) was dissolved in dry DCM (50 mL) and cooled to 0 °C. TiCl4 (0.82 mL, 7.43 mmol) was added dropwise. After stirring for 30 min, the resulting yellow suspension was cooled to −40 °C. i-Pr2NEt (1.32 mL, 7.97 mmol) was then added dropwise, and the reaction mixture was stirred for 2 h at this temperature. The resulting solution was then cooled to −90 °C. 5 (1.44 g, 3.71 mmol) was dissolved in dry DCM (20 mL) and added dropwise to the reaction mixture. The reaction mixture was stirred at −90 °C for 3 h and quenched by the addition of a saturated aqueous solution of NH4Cl. The reaction mixture was then allowed to warm to room temperature and extracted three times with DCM (20 mL × 3). The combined organic layers were washed with brine, dried over Na2SO4, filtered, and the solvent evaporated under reduced pressure. The resulting crude was purified by flash chromatography on silica gel, eluting with PE/EA (8/1) to afford 8 (1.33 g, 59%) and 9 (0.656 g, 29%) as yellow oils, respectively.
For 8: Rf = 0.19 (PE/EA 4/1). [α]20D: −78.0 (c 3.7, CHCl3). 1H-NMR (400 MHz, CDCl3): δ 7.29 (m, 20H), 5.33 (m, 1H), 4.86 (dd, J = 36.8, 7.1 Hz, 1H), 4.63 (brs, 1H), 3.67 (m, 1H), 3.47 (dd, J = 17.9, 8.8 Hz, 1H), 3.36 (dd, J = 11.2, 7.2 Hz, 1H), 3.21 (m, 1H), 3.03 (m, 1H), 2.95 (d, J = 4.1 Hz, 1H), 2.87 (d, J = 11.6 Hz, 1H), 2.19 (m, 4H). 13C-NMR (150 MHz, CDCl3): δ 201.27, 172.02, 158.60 (d, 1JC-F = 257.2 Hz), 144.87, 136.32, 129.60, 129.45, 128.97, 127.88, 127.34, 126.63, 104.96 (d, 2JC-F = 12.9 Hz), 68.32, 66.63, 42.81, 36.79, 32.18, 31.52, 22.72. 19F-NMR (376 MHz, CDCl3): δ –129.15 (dd, J = 32.1, 18.2 Hz). ESI-MS (m/z): 650.4 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C36H34FNO2S3Na: 650.1628, found: 650.1621.
For 9: Rf = 0.30 (PE/EA 4/1). [α]20D: −65.4 (c 0.30, CHCl3). 1H-NMR (400 MHz, CDCl3): δ 7.30 (m, 20H), 5.37 (m, 1H), 4.85 (dt, J = 37.2, 7.0 Hz, 1H), 4.56 (brs, 1H), 3.75 (dd, J = 17.5, 9.2 Hz, 1H), 3.41 (m, 2H), 3.21 (m, 2H), 3.03 (dd, J = 13.2, 10.4 Hz, 1H), 2.89 (d, J = 11.6 Hz, 1H), 2.19 (m, 4H). 13C-NMR (150 MHz, CDCl3): δ 201.27, 172.02, 158.60 (d, 1JC-F = 257.2 Hz), 144.87, 136.32, 129.60, 129.45, 128.97, 127.88, 127.34, 126.63, 104.96 (d, 2JC-F = 12.9 Hz), 68.32, 66.63, 42.81, 36.79, 32.18, 31.52, 22.72. ESI-MS (m/z): 650.4 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C36H34FNO2S3Na: 650.1628, found: 650.1621.
(R)-Methyl 2′-(((S/R,Z)-4-fluoro-3-hydroxy-7-(tritylthio)hept-4-enamido)methyl)-4-methyl-4,5-dihydro-[2,4′-bithiazole]-4-carboxylate (31S/31R) (11)
To a stirring solution of 10 (0.459 g, 1.28 mmol) and DMAP (0.408 g, 3.34 mmol) in anhydrous DCM (20 mL) a solution of 8 (0.820 g, 1.28 mmol) in DCM (20 mL) was added dropwise at rt, and the resultant solution was stirred for another 2 h. The solution was then quenched with NH4Cl saturated solution (20 mL) and separated, and the aqueous phase was extracted with DCM (30 mL × 3). The combined organic phase was washed successively with H2O, brine, dried with Na2SO4 and filtered. After removal of the solvent, the residue was purified by flash chromatography on silica gel with DCM/EA (2/1) to yield 11 (0.600 g, 70%) as a foamy solid.
Rf = 0.26 (PE/EA 1/1). [α]20D: −32.2 (c 3.6, CHCl3). 1H-NMR (400 MHz, CDCl3): δ 7.89 (s, 1H), 4.79 (m, 2H), 4.68 (m, 2H), 4.49 (brs, 1H), 3.87 (d, J = 11.4 Hz, 1H), 3.79 (s, 3H), 3.27 (d, J = 11.4 Hz, 1H), 2.56 (m, 2H), 2.15 (m, 5H), 1.63 (s, 3H). 13C-NMR (100 MHz, CDCl3): δ 173.62, 171.49, 167.63, 162.78, 158.92 (d, 1JC-F = 257.4 Hz), 148.20, 144.83, 129.58, 127.91, 126.67, 122.56, 104.67 (d, 2JC-F = 12.3 Hz), 84.49, 66.97 (d, 2JC-F = 33 Hz), 66.62, 53.01, 41.54, 40.80, 39.72, 31.49, 24.02, 22.70 (d, 3JC-F = 3.5 Hz). 19F-NMR (376 MHz, CDCl3): δ −124.95 (dd, J = 36.2, 20.3 Hz). ESI-MS (m/z): 712.4 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C36H36FN3O4S3Na: 712.1744, found: 712.1748.
(R)-Methyl 2′-((5S/R,8S)-1-(9H-fluoren-9-yl)-8-((Z)-1-fluoro-4-(tritylthio)but-1-en-1-yl)-5-isopropyl-3,6,10-trioxo-2,7-dioxa-4,11-diazadodecan-12-yl)-4-methyl-4,5-dihydro-[2,4′-bithiazole]-4-carboxylate (13a)
To a solution of Fmoc-Val-OH (0.165 g, 0.49 mmol) and DMAP (0.005 g, 0.041 mmol) in DCM (15 mL) 2,4,6-trichlorobenzoyl chloride (0.089 mL, 0.568 mmol) was added at 0 °C, and then the solution continued to stirred for 1 h. Then. a solution of 11 and DIPEA (0.11 mL, 0.65 mmol) in DCM (10 mL) was added to the stirring mixture. The reaction was allowed to warm to rt and stirred for 1 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 successively 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 (5/4) to afford 13a (0.266 g, 65%) as a white foamy solid. Rf = 0.26 (PE/EA 1/1). [α]20D: −16.4 (c 0.34, CHCl3). 1H-NMR (600 MHz, CDCl3): δ 7.89 (s, 1H), 7.75 (d, J = 7.2 Hz, 2H), 7.57 (d, J = 3.6 Hz, 2H), 7.38 (m, 8H), 7.34–7.24 (m, 8H), 7.20 (t, J = 7.1 Hz, 3H), 6.64 (brs, 1H), 5.67–5.79 (m, 1H), 5.25 (brs, 1H), 4.92 (dt, J = 35.9, 7.0 Hz, 1H), 4.68 (m, 2H), 4.37 (m, 2H),4.20 (t, J = 6.9 Hz, 1H), 4.16 (dd, J = 7.6, 5.8 Hz, 1H), 3.85 (d, J = 11.3 Hz, 1H), 3.78 (s, 3H), 3.24 (d, J = 11.3 Hz, 1H), 2.70 (m, 2H), 2.01–2.24 (m, 5H), 1.63 (s, 3H), 0.88 (t, J = 6.5 Hz, 3H), 0.83 (d, J = 6.6 Hz, 3H). 13C-NMR (150 MHz, CDCl3): δ 173.62, 170.92, 168.24, 167.81, 162.77, 156.29, 153.75 (d, 1JC-F = 257.4 Hz), 148.35, 144.78, 143.79 (d, JC-F = 19.3 Hz), 141.33, 129.58, 127.91, 127.82 (d, JC-F = 24.5 Hz), 127.12, 126.68, 125.08, 122.33, 120.00, 109.63 (d, 2JC-F = 12.0 Hz), 84.56, 69.62 (d, 3JC-F = 28.5 Hz), 67.08, 66.71, 59.17, 52.91, 47.19, 41.53, 41.09, 38.02, 31.59, 31.10 (d, J = 10.2 Hz), 23.98, 22.79, 22.66, 18.81, 17.71. 19F NMR (376 MHz, CDCl3): δ −125.77 (dd, J = 35.4, 21.1 Hz). ESI-MS (m/z): 1011.2 [M + H]+. HRMS-ESI (m/z): [M+Na]+ calcd. for C56H55FN4O7S3Na: 1033.3109, found: 1033.3102.
For 13b: 60%, Rf = 0.26 (PE/ EA 1/1). [α]20D: −4.7 (c = 0.097, CHCl3). 1H-NMR (600 MHz, CDCl3) δ 7.89 (s, 1H), 7.76 (d, J = 7.5 Hz, 2H), 7.53 (t, J = 7.2 Hz, 2H), 7.39 (d, J = 7.4 Hz, 8H), 7.33–7.25 (m, 9H), 7.19 (dd, J = 16.7, 7.7 Hz, 6H), 7.04 (d, J = 6.9 Hz, 2H), 6.60 (s, 1H), 5.77–5.57 (m, 1H), 5.26 (d, J = 7.5 Hz, 1H), 4.81 (dt, J = 36.0, 7.0 Hz, 1H), 4.70–4.61 (m, 2H), 4.52 (dd, J = 12.9, 6.3 Hz, 1H), 4.45–4.27 (m, 2H), 4.18 (t, J = 6.8 Hz, 1H), 3.86 (d, J = 11.3 Hz, 1H), 3.78 (s, 3H), 3.25 (d, J = 11.3 Hz, 1H), 3.03 (m, 2H), 2.66 (m, 2H), 2.18 (t, J = 6.5 Hz, 3H), 2.15–2.07 (m, 2H), 1.63 (s, 4H). 13C-NMR (150 MHz, CDCl3) δ 172.56, 169.70, 167.54, 167.03, 162.15, 154.99 (d, J = 11.5 Hz), 154.46 (d, J = 14.7 Hz), 152.56 (d, J = 74.3 Hz), 147.53 (d, J = 54.5 Hz), 144.14, 143.09 (d, J = 14.9 Hz), 140.69, 134.75, 128.94, 128.73, 127.94, 127.29, 127.11, 126.50 (d, J = 7.5 Hz), 126.07, 124.44 (d, J = 7.6 Hz), 121.71, 119.37, 109.04 (d, J = 12.3 Hz), 83.92, 69.32 (d, J = 29.3 Hz), 66.25 (d, J = 46.7 Hz), 54.26, 52.28, 46.50, 40.89, 40.41, 37.41, 37.18, 30.43, 23.36, 22.31. 19F-NMR (376 MHz, CDCl3): δ −126.27 (dd, J = 35.4, 21.1 Hz). ESI-MS (m/z): 1059.2 [M + H]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C60H55FN4O7S3Na:1081.3109, found: 1081.3126.
(5R,8S,11S/R)-11-((Z)-1-Fluoro-4-(tritylthio)but-1-en-1-yl)-8-isopropyl-5-methyl-10-oxa-3,17-dithia-7,14,19,20-tetraazatricyclo[14.2.1.12,5]icosa-1(18),2(20),16(19)-triene-6,9,13-trione (14a)
To a solution of 13a (0.420 g, 0.42 mmol) in THF/H2O (4/1, v/v, 20 mL) LiOH∙H2O (0.027 g, 0.63 mmol) was added at 0 °C, and the reaction mixture was stirred for 3 h at that temperature. After the hydrolysis was completed, the reaction mixture was quenched with 1.0 M HCl aqueous solution (1.0 mL), and then extracted with DCM (20 mL × 3). The combined organic layers were washed successively with water, brine, dried with Na2SO4 and filtered. After evaporation, the residue was purified by flash chromatography on silica gel, eluting with DCM/MeOH (40/1 to 10/1) to afford the resultant acid (0.251 g) as a white foamy solid.
The resultant acid (0.251 g) was dissolved in dry DCM (20 mL), and Et2NH (1.0 mL) was added at rt. After stirring for 3 h and removal of the solvent, toluene (10 mL) was added and evaporated under reduced pressure, and this operation was repeated three times to remove the remaining Et2NH, affording the crude product.
Then, the crude amino acid was dissolved in dry DCM (100 mL), and the solution was added dropwise to a stirring solution of HATU (0.380 g, 1.0 mmol), HOAT (0.136 g, 1.0 mmol), and DIPEA (0.33 mL, 2.0 mmol) in DCM (300 mL) at rt. The reaction mixture was stirred at rt for 12 h. The solution was concentrated under reduced pressure, and this resultant solution (100 mL) was washed with saturated NH4Cl solution, water, 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/MeOH (20/20/8) to afford 14a (31%, over three steps) as a white foamy solid. Rf = 0.15 (PE/EA 2/3). [α]20D −14.3 (c 0.4, CHCl3). 1H-NMR (600 MHz, CDCl3): δ 7.76 (s, 1H), 7.29 (m, 15H), 7.13 (d, J = 9.2 Hz, 1H), 6.41 (d, J = 7.6 Hz, 1H), 5.60 (dd, J = 20.2, 10.5 Hz, 1H), 5.29 (dd, J = 17.5, 9.7 Hz, 1H), 5.00 (m, 1H), 4.62 (d, J = 7.6 Hz, 1H), 4.20 (d, J = 18.1 Hz, 1H), 4.04 (d, J = 11.0 Hz, 1H), 3.28 (d, J = 11.3 Hz, 1H), 3.12 (m, 1H), 2.70 (d, J = 16.6 Hz, 1H), 2.15 (m, 5H), 1.85 (s, 3H), 0.68 (d, J = 6.4 Hz, 3H), 0.49 (d, J = 6.6 Hz, 3H). 13C-NMR (150 MHz, CHCl3): δ 173.60, 168.94, 168.76, 167.89, 164.58, 155.25 (d, 1JC-F = 256 Hz), 147.49, 129.58, 127.91, 126.65, 124.33, 109.26 (d, 2JC-F = 12.4 Hz), 84.39, 69.95 (d, 3JC-F = 29.6 Hz), 57.58, 43.32, 41.13, 38.63, 37.49, 34.23, 31.12, 29.72, 24.13, 22.88, 18.84, 16.57, 14.22. 19F NMR (376 MHz, CDCl3): δ –124.95 (dd, J = 36.2, 20.3 Hz). ESI-MS (m/z): 779.4 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C40H41FN4O4S3Na: 779.2166, found: 779.2171.
For 14b: 22%, Rf = 0.15 (PE/EA 2/3). [α]20D: + 28.6 (c 0.021, CHCl3), 1H-NMR (600 MHz, CDCl3) δ 7.61 (s, 1H), 7.38 (d, J = 7.6 Hz, 6H), 7.27 (dd, J = 11.0, 4.3 Hz, 6H), 7.20 (t, J = 7.3 Hz, 3H), 7.13 (d, J = 7.7 Hz, 1H), 6.94–6.70 (m, 5H), 6.15 (d, J = 8.3 Hz, 1H), 5.71 (m, J = 18.9, 10.1, 1.9 Hz, 1H), 5.05 (d, 12 Hz, 1H), 5.00 (dt, 36 Hz, 7.5Hz, 1H), 4.88 (m, 1H), 4.17 (dd, J = 17.4, 2.8 Hz, 1H), 4.08 (d, J = 11.3 Hz, 1H), 3.25 (d, J = 11.3 Hz, 1H), 3.20 (dd, J = 14.0, 23 Hz, 1H), 3.06 (dd, J = 14.0, 5.9 Hz, 1H), 2.99 (dd, J = 16.4, 10.2 Hz, 1H), 2.62 (dd, J = 16.4, 2.1 Hz, 1H), 2.17 (dt, J = 11.0, 4.0 Hz, 2H), 2.10 (dt, J = 14.4, 7.2 Hz, 2H), 1.79 (s, 3H). 13C-NMR (150 MHz, CDCl3): δ 173.67, 168.89, 168.16, 166.97, 163.73, 155.33, 153.63, 147.26, 144.78, 135.11, 129.60 (d, J = 8.8 Hz), 127.88 (d, J = 7.6 Hz), 126.65, 125.93, 123.68, 109.17 (d, J = 12.5 Hz), 84.19, 70.18 (d, J = 30.9 Hz), 66.61, 54.19, 42.46, 40.98, 37.70, 37.46, 31.12, 24.98, 22.88 (d, J = 3.8 Hz). 19F-NMR (376 MHz, CDCl3): δ –124.43 (dd, J = 36.2, 20.3 Hz). ESI-MS (m/z): 827.2 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C44H41FN4O4S3Na: 827.2166, found: 827.2166.
(5R,8S,11S/R)-11-((Z)-1-Fluoro-4-mercaptobut-1-en-1-yl)-8-isopropyl-5-methyl-10-oxa-3,17-dithia-7,14,19,20-tetraazatricyclo[14.2.1.12,5]icosa-1(18),2(20),16(19)-triene-6,9,13-trione (15a)
14a (50 mg, 0.066 mmol) was dissolved in dry DCM (15 mL) and cooled to 0 °C. The mixture was successively treated with Et3SiH (27 µL, 0.13 mmol) and TFA (0.30 mL, 4.0 mmol). The reaction mixture was allowed to warm to room temperature and stirred for 1.5 h before being concentrated and chromatographed (EtOAc) to provide a clear oil (15 mg, 0.03 mmol). 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 were 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 15a in 67% yield as a white foamy solid. Rf = 0.42 (PE/EA 2/3). 1H-NMR (600 MHz, CDCl3): δ 7.78 (s, 1H), 7.14 (d, J = 9.5 Hz, 1H), 6.51 (d, J = 7.3 Hz, 1H), 5.67 (dd, J = 20.2, 11.0 Hz, 1H), 5.32 (dd, J = 17.5, 9.7 Hz, 2H), 5.15 (dt, J = 36.5, 7.5 Hz, 1H), 4.65 (dd, J = 9.4, 3.2 Hz, 1H), 4.26 (dd, J = 17.5, 2.8 Hz, 1H), 4.05 (d, J = 11.4 Hz, 1H), 3.30 (d, J = 11.4 Hz, 1H), 3.17 (m, 2H), 2.76 (d, J = 16.4 Hz, 1H), 2.56 (m, 3H), 2.42 (m, 2H), 2.15 (m, 5H), 1.87 (s, 3H), 0.69 (d, J = 6.9 Hz, 3H), 0.50 (d, J = 6.8 Hz, 3H). ESI-MS (m/z): 515.2 [M + H]+. HRMS-ESI (m/z): [M + H]+ calcd. for C21H27FN4O4S3H: 515.1251, found: 515.1252.
For 15b: 59%, Rf = 0.42 (PE/ EA 2/3). 1H-NMR (600 MHz, CDCl3) δ 7.66 (s, 1H), 7.19 (m, 2H), 6.84 (m, 5H), 6.15 (s, 1H), 5.78 (dd, J = 17.9, 9.4 Hz, 1H), 5.16 (dt, J = 36.3, 7.5 Hz, 1H), 5.04 (dd, J = 17.4, 8.2 Hz, 1H), 4.93 (m, 1H), 4.27 (d, J = 17.1 Hz, 1H), 4.11 (d, J = 11.2 Hz, 1H), 3.26 (d, J = 11.3 Hz, 1H), 3.22 (dd, J = 14.0, 3.0 Hz, 1H), 3.12–3.08 (m, 1H), 3.07 (d, J = 5.9 Hz, 1H), 2.67 (d, J = 14.8 Hz, 1H), 2.54 (dd, J = 14.4, 7.1 Hz, 1H), 2.40 (m, 2H), 1.83 (s, 3H). ESI-MS (m/z): 563.0 [M + H]+. HRMS-ESI (m/z): [M + H]+ calcd. for C25H27FN4O4S3H: 563.1251, found: 563.1254.
S-((Z)-4-Fluoro-4-((5R,8S,11S/R)-8-isopropyl-5-methyl-6,9,13-trioxo-10-oxa-3,17-dithia-7,14,19,20-tetraazatricyclo[14.2.1.12,5]icosa-1(18),2(20),16(19)-trien-11-yl)but-3-en-1-yl) octanethioate (16a)
The free thiol 15a (26 mg) was dissolved in dry DCM (10 mL) and cooled to 0 °C. The mixture was successively treated with Et3N (14 µL, 0.1 mmol) and octanoyl chloride (42 µL, 0.25 mmol). 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 were washed successively 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 16a (61%) as a white foamy solid. Rf = 0.42 (DCM/EA 3/1). [α]20D: +34.3 (c 0.3, CHCl3). 1H-NMR (600 MHz, CDCl3): δ 7.78 (s, 1H), 7.13 (d, J = 9.5 Hz, 1H), 6.42 (d, J = 7.8 Hz, 1H), 5.65 (m, 1H), 5.32 (dd, J = 17.5, 9.8 Hz, 1H), 5.10 (dt, J = 7.2, 2 Hz, 1H), 4.65 (dd, J = 9.3, 2.9 Hz, 1H), 4.26 (dd, J = 17.5, 2.8 Hz, 1H), 4.05 (d, J = 11.3 Hz, 1H), 3.28 (d, J = 11.3 Hz, 1H), 3.16 (dd, J = 16.4, 11.4 Hz, 1H), 2.90 (t, J = 7.1 Hz, 2H), 2.74 (d, J = 14.8 Hz, 1H), 2.54 (t, J = 7.5 Hz, 2H), 2.37 (m, 2H), 2.13 (m, 1H), 1.88 (s, 3H), 1.65 (m, 2H), 1.28 (m, 8H), 0.88 (m, 3H), 0.68 (d, J = 6.7 Hz, 3H), 0.49 (d, J = 6.7 Hz, 3H). 13C-NMR (150 MHz, CDCl3): δ 199.35, 173.64, 168.96, 168.84, 167.90, 164.62, 155.25 (d, J = 256 Hz), 147.49, 124.41, 108.71 (d, J = 12.6 Hz), 84.40, 69.95 (d, J = 29.6 Hz), 57.54, 44.17, 43.35, 41.17, 37.47, 34.33, 31.63, 28.92, 27.9, 25.64, 24.13, 23.86, 22.61, 18.86, 16.51, 14.09. 19F NMR (376 MHz, CDCl3): δ −124.76 (dd, J = 35.9, 20.9 Hz). ESI-MS (m/z): 663.3 [M + Na]+. HRMS-ESI (m/z): [M + Na]+ calcd. for C40H41FN4O4S3Na: 663.2115, found: 663.2139.
For 16b: 66%, Rf = 0.42 (DCM/EA 3/1). [α]20D: +36.6 (c 0.025, CHCl3). 1H-NMR (150 MHz, CDCl3) δ 7.64 (s, 1H), 7.14 (d, J = 7.7 Hz, 2H), 7.00–6.74 (m, 5H), 6.15 (d, J = 8.0 Hz, 1H), 5.76 (dd, J = 19.2, 9.9 Hz, 1H), 5.12 (dt, J = 36.3Hz, 7.5 Hz, 1H), 5.06 (d, J = 9.0 Hz, 1H), 4.92 (t, J = 8.1 Hz, 1H), 4.92 (t, J = 8.1 Hz, 1H), 4.24 (dd, J = 17.4, 2.1 Hz, 1H), 4.10 (d, J = 11.2 Hz, 1H), 3.23 (d, J = 11.2 Hz, 1H), 3.21 (d, J = 2.8 Hz, 1H), 3.06 (m, 2H), 2.88 (t, J = 7.1 Hz, 2H), 2.66 (d, J = 16.0 Hz, 1H), 2.53 (t, J = 7.5 Hz, 2H), 2.36 (dd, J = 14.4, 7.2 Hz, 2H), 1.83 (s, 3H), 1.64 (dd, J = 14.0, 7.0 Hz, 3H), 1.27 (m, 8H), 0.89 (dd, J = 9.0, 4.6 Hz, 3H). 13C-NMR (150 MHz, CDCl3): δ 198.61, 173.12, 168.27, 167.47, 166.35, 163.04, 146.63 (d, J = 28.5 Hz), 134.52, 129.03, 127.22, 125.29, 123.03, 107.82 (d, J = 23.4 Hz), 83.63, 69.52 (d, J = 30.9 Hz), 53.57, 43.52, 41.84, 40.37, 37.00 (d, J = 18.3 Hz), 30.98, 29.07, 28.27, 27.27, 24.99, 24.35, 23.20, 21.95, 13.45 (d, J = 8.6 Hz). 19F-NMR (376 MHz, CDCl3): δ −124.76 (dd, J = 36.1, 19.3 Hz). ESI-MS (m/z): 689.2 [M + H]+. HRMS-ESI (m/z): [M + H]+ calcd. for C33H41FN4O5S3: 689.2296, found: 689.2302.