5 Experimental Part
5.2 General Synthetic Procedures
5.3.4 Synthesis of Fmoc- D -β 3 -hTOPP-OH
4-Hydroxy-D-phenylglycine (50) (5.00 g, 29.9 mmol, 1.00 eq) was dissolved in an aqueous solution of Na2CO3 (10%, 67 mL) and cooled to 0 °C. CbzCl (4.48 mL, 5.42 g, 31.7 mmol, 1.06 eq) in toluene (4.48 mL) and dioxane (50.0 mL) was added drop-wise to the solution. The final reaction mixture was stirred at 0 °C for 30 min and then at rt for 1 h. The organic solvent was evaporated. Ice-water (166 mL) was added to the aqueous phase and it was washed with EtOAc (3 x 50.0 mL). Afterwards, the aqueous phase was acidified with 2 M aq HCl to pH 2 and extracted with EtOAc (3 x 75.0 mL). The combined organic phases were washed with water (50.0 mL), saturated aq NaCl solution (50.0 mL) and then dried over MgSO4. Finally, evaporation of the solvent under reduced pressure gave compound 51 (8.35 g, 27.7 mmol, 93%) as a colourless solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 12.51 (s, 1 H, COOH), 9.52 (s, 1 H, aromatic OH), 7.89 (d, 3JHH = 8.0 Hz, 1 H, NH), 7.55‒7.26 (m, 5 H, aromatic CH), 7.23 (d,
3JHH = 8.5 Hz, 2 H, aromatic CH), 6.76 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 5.17‒4.98 (m, 3 H, CH2, -CH).
13C-NMR (75 MHz, DMSO-d6): (ppm) = 172.50 (COOH), 157.19 (aromatic C-OH), 155.82 (CONH), 137.00, 128.97, 128.33, 127.80, 127.71, 127.28, 127.18, 115.18 (aromatic C), 65.56 (CH2), 57.61 (-C).
165 ESI-MS: m/z = 302.1 [M+H]+, 324.1 [M+Na]+, 625.2 [2M+Na]+, 300.1 [M-H]-, 601.2 [2M-H]-.
ESI-HRMS: m/z calculated for C16H15NO5Na [M+Na]+: 324.0842, found: 324.0843.
166
5.3.4.2 Cbz-D-Hpg(TBDMS)-OH (52)
Under an argon atmosphere, amino acid 51 (3.00 g, 9.97 mmol, 1.00 eq) and imidazole (1.70 g, 24.9 mmol, 2.50 eq) were dissolved in dry DMF (6.00 mL). Then, TBDMSCl (1.80 g, 11.9 mmol, 1.20 eq) was added and the final reaction mixture was stirred at rt for 25 h. Afterwards, the mixture was diluted with EtOAc (50.0 mL) and H2O (50.0 mL) and the two phases were separated. The aqueous phase was extracted with EtOAc (3 x 50.0 mL). The combined organic phases were washed with saturated aq NaCl solution (50.0 mL) and then dried over MgSO4. Afterwards, the solvent was evaporated under reduced pressure. Purification by flash-column chromatography (DCM/MeOH/AcOH, 9:1:0.1 7:1:0.1) gave the pure product 52 (2.70 g, 6.58 mmol, 66%) as a white solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 7.90 (d, 3JHH = 7.9 Hz, 1 H, NH), 7.41‒7.24 (m, 7 H, aromatic CH), 6.81 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 5.11‒5.00 (m, 3 H, CH2, -CH), 0.95 (s, 9 H, 3 x CH3), 0.19 (s, 6 H, 2 x CH3).
13C-NMR (126 MHz, DMSO-d6): (ppm) = 172.11 (COOH), 155.65 (Cbz CONH), 154.66 (aromatic C-O(TBDMS)), 136.88, 130.14, 128.90, 128.21, 127.67, 127.59, 119.48 (aromatic C), 65.45 (CH2), 57.49 (-C), 25.46 (C(CH3)3), 17.69 (C(CH3)3), -4.63 (CH3).
ESI-MS: m/z = 416.2 [M+H]+, 438.2 [M+Na]+, 853.3 [2M+Na]+, 300.1 [M-H]-, 601.2 [2M-H]-.
167 ESI-HRMS: m/z calculated for C22H29NO5SiNa [M+Na]+: 438.1707, found: 438.1696.
168
5.3.4.3 Cbz-D-Hpg(TBDMS)-CHN2 (53)
Amino acid 52 (3.99 g, 9.60 mmol, 1.00 eq) was dissolved in dry THF (48.0 mL) under an argon atmosphere and cooled down to -15 °C. Subsequently, Et3N (1.07 mL, 1.46 g, 10.6 mmol, 1.10 eq) and isobutyl chloroformate (1.44 mL, 1.37 g, 10.6 mmol, 1.10 eq) were added to the mixture and stirred at -15 °C for 45 min. The reaction was warmed up to 0 °C and then treated with diazomethane solution (0.60 M in Et2O, 32.0 mL, 2.00 eq) under light exclusion. The reaction mixture was stirred at 0 °C for 30 min.
Afterwards, the mixture was warmed up to rt and stirred at rt for 5 h. The reaction was quenched with AcOH (2.20 mL, 2.30 g, 53.2 mmol, 4.00 eq). Then 6% aq NaHCO3
solution (100 mL) and EtOAc (50.0 mL) were added. The phases were separated, and the aqueous phase was extracted with EtOAc (2 x 50.0 mL). The combined organic phases were washed with saturated aq NH4Cl solution (3 x 50.0 mL), saturated aq NaCl solution (3 x 50.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure. Purification by flash-column chromatography (pentane/EtOAc, 7:1 3:1) gave the desired compound 53 (2.98 g, 6.78 mmol, 61%) as a yellow oil.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 8.04 (d, 3JHH = 8.2 Hz, 1 H, NH), 7.43‒7.23 (m, 7 H, aromatic CH), 6.82 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 6.11 (s, 1 H, CH), 5.22 (d,
3JHH = 8.2 Hz, 1 H, -CH), 5.06 (s, 2 H, CH2), 0.95 (s, 9 H, 3 x CH3), 0.19 (s, 6 H, 2 x CH3).
13C-NMR (75 MHz, DMSO-d6): (ppm) = 192.38 (COCHN2), 155.65 (Cbz CONH), 154.85
169 (aromatic C-O(TBDMS)), 136.77, 129.64, 129.13, 128.21, 127.70, 127.63, 119.66 (aromatic C), 65.62 (CH2), 61.42 (-C), 53.52 (COCHN2), 25.43 (C(CH3)3), 17.79 (C(CH3)3), -4.65 (CH3).
ESI-MS: m/z = 462.2 [M+Na]+, 901.3 [2M+Na]+, 438.2 [M-H]-.
ESI-HRMS: m/z calculated for C23H29N3O4SiNa [M+Na]+: 462.1820, found: 462.1819.
170
5.3.4.4 Cbz-D-β3-hHpg(TBDMS)-OH (54)
Diazo ketone 53 (2.57 g, 5.90 mmol, 1.00 eq) was dissolved in THF/H2O (9:1, 24.0 mL), cooled to 0 °C and then treated with AgOCOPh (110 mg, 470 mol, 0.08 eq) under light exclusion and sonication at rt for 2 h. Afterwards, H2O (50.0 mL) and EtOAc (50.0 mL) were added and the aqueous phase was acidified with 2 M aqHCl solution to a pH of 2.
Then, the aqueous phase was extracted with EtOAc (3 x 50.0 mL). The combined organic phases were washed with saturated aq NaCl solution (3 x 50.0 mL) and dried over MgSO4. The solvent was removed under reduced pressure to give the Cbz-protected -amino acid 54 (2.48 g, 5.80 mmol, 98%) as a yellowish oil.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 12.17 (sbr, 1 H, COOH), 7.78 (d, 3JHH = 8.7 Hz, 1 H, NH), 7.43‒7.27 (m, 5 H, aromatic CH), 7.21 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 6.78 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 5.03‒4.87 (m, 3 H, -CH, CH2), 2.75‒2.55 (m, 2 H,
-CH2), 0.95 (s, 9 H, 3 x CH3), 0.18 (s, 6 H, 2 x CH3).
13C-NMR (75 MHz, DMSO-d6): (ppm) = 171.61 (COOH), 155.20 (Cbz CONH), 153.98 (aromatic C-OTBDMS), 137.02, 135.57, 128.22, 127.65, 127.59, 127.55, 119.36 (aromatic C), 65.21 (CH2), 59.66 (-CH2), 51.03 (-CH), 25.49 (C(CH3)3), 17.83 (C(CH3)3), -4.61 (CH3).
ESI-MS: m/z = 430.2 [M+H]+, 452.2 [M+Na]+, 881.4 [2M+Na]+, 428.2 [M-H]-. ESI-HRMS: m/z calculated for C23H31NO5SiNa [M+Na]+: 452.1864, found: 452.1855.
171 5.3.4.5 Cbz-D-β3-hHpg-OBn (59)
To amino acid 54 (500 mg, 1.16 mmol, 1.00 eq) dissolved in DCM (3.00 mL), BnOH (1.50 mL) and conc. HCl (37%, 14.5 mL) were added. The final reaction mixture was stirred at rt for 4 h. Then, H2O (50.0 mL) and EtOAc (50.0 mL) were added and the aqueous phase was extracted with EtOAc (3 x 50.0 mL). The combined organic phases were washed with saturated aq NaCl solution (3 x 20.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure. After purification by flash-column chromatography (pentane/EtOAc, 5:1 1:1) the desired product 59 (240 mg, 580 mol, 50%) was obtained as a colourless solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 9.29 (s, 1 H, aromatic C-OH), 7.80 (d,
3JHH = 8.8 Hz, 1 H, NH), 7.44‒7.21 (m, 10 H, aromatic CH), 7.13 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 6.70 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 5.08‒4.89 (m, 5 H, -CH, 2 x CH2), 2.97‒2.62 (m, 2 H, -CH2).
13C-NMR (75 MHz, DMSO-d6): (ppm) = 170.03 (COOBn), 156.45 (aromatic C-OH), 155.19 (Cbz CONH), 137.00, 135.99, 132.52, 128.26, 128.23, 127.80, 127.69, 127.63, 127.62, 127.60, 127.46, 114.97 (aromatic CH), 65.40, 65.27 (CH2), 51.18 (-CH), 41.18 (-CH2).
ESI-MS: m/z = 406.2 [M+H]+, 428.2 [M+Na]+, 833.3 [2M+Na]+.
ESI-HRMS: m/z calculated for C24H23NO5Na [M+Na]+: 428.1468, found: 428.1450.
172
5.3.4.6 Cbz-D-β3-hHpg-OBn (59)
The benzyl protection was performed according to the procedure described by MATTHIAS KRULL.[141] Therefore, diazo ketone 53 (5.55 g, 12.6 mmol, 1.00 eq) was dissolved in dry THF/BnOH (9:1, 24.0 mL), cooled to 0 °C and then treated with AgOCOPh (230 mg, 1.01 mmol, 0.08 eq) under light exclusion and sonication at rt for 2 h. Afterwards, H2O (100 mL) and EtOAc (100 mL) were added. The aqueous phase was acidified with 2 M
aq HCl solution to a pH of 2. Then, the aqueous phase was extracted with EtOAc (3 x 75.0 mL) and the combined organic phases were washed with saturated aq NaCl solution (3 x 50.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure to give the benzyl-protected -amino acid. The crude TBDMS-protected product containing residual BnOH was dissolved in MeOH (142 mL), conc. HCl (37%, 15.8 mL) was added and the final reaction mixture was stirred at rt for 1 h. Then, H2O (100 mL) and EtOAc (100 mL) were added and the aqueous phase was extracted with EtOAc (3 x 100 mL). The combined organic phases were washed with saturated aq NaCl solution (3 x 50.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure. After purification by flash-column chromatography (pentane/EtOAc, 3:1 1:1) the desired product 59 (3.57 g, 8.82 mmol, 70%) was isolated as a colourless solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 9.29 (s, 1 H, aromatic C-OH), 7.80 (d,
3JHH = 8.9 Hz, 1 H, NH), 7.42‒7.20 (m, 10 H, aromatic CH), 7.13 (d, 3JHH = 8.5 Hz, 2 H,
173 aromatic CH), 6.70 (d, 3JHH = 8.5 Hz, 2 H, aromatic CH), 5.14‒4.83 (m, 5 H, -CH, 2 x CH2), 2.94‒2.61 (m, 2 H, -CH2).
13C-NMR (75 MHz, DMSO-d6): (ppm) = 169.98 (COOBn), 156.39 (aromatic C-OH), 155.14 (Cbz CONH), 136.77, 135.95, 132.47, 128.22, 128.19, 127.76, 127.65, 127.59, 127.56, 127.41, 127.34, 114.92 (aromatic C), 65.35, 65.22 (CH2), 51.13 (-CH), 41.13 (-CH2).
ESI-MS: m/z = 406.2 [M+H]+, 428.2 [M+Na]+, 833.3 [2M+Na]+, 404.2 [M-H]-. ESI-HRMS: m/z calculated for C24H23NO5Na [M+Na]+: 428.1468, found: 428.1459.
174
5.3.4.7 Cbz-D-β3-hHpg(Tf)-OBn (61)
To a 0 °C cooled solution of Cbz-D-3-hHpg-OBn (59) (4.79 g, 11.8 mmol, 1.00 eq) and pyridine (2.75 mL, 2.69 g, 35.4 mmol, 3.0 eq) in dry DCM (36.0 mL) Tf2O (5.00 g, 17.7 mmol, 1.50 eq) was added slowly and stirred at 0 °C for 15 min. The mixture was warmed up to rt and stirred at rt for 20 min. The reaction mixture was quenched with saturated aq NaHCO3 solution and the resulting aqueous phase was extracted with DCM (3 x 50.0 mL). The combined organic phases were washed with saturated aq NaCl solution (3 x 50.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure. The pyridine was removed as an azeotropic mixture with toluene to give the product 61 (6.26 g, 11.6 mmol, 99%) as brown solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 8.03 (d, 3JHH = 8.5 Hz, 1 H, NH), 7.53 (d,
3JHH = 8.8 Hz, 2 H, aromatic CH), 7.43 (d, 3JHH = 8.8 Hz, 2 H, aromatic CH), 7.39‒7.17 (m, 10 H, aromatic CH), 5.15‒4.94 (m, 5 H, -CH, CH2), 2.98‒2.74 (m, 2 H, -CH2).
13C-NMR (125 MHz, DMSO-d6): (ppm) = 169.71 (COOBn), 155.30 (Cbz CONH), 148.11, 143.23, 136.82, 135.88, 128.69, 128.34, 128.25, 128.23, 127.87, 127.74, 127.65, 121.28 (aromatic C), 118.20 (q, 1JCF = 318.8 Hz, CF3), 65.59, 65.48 (CH2), 51.35 (-C), 40.50 ( -CH2).
19F-NMR (282 MHz, DMSO-d6): (ppm) = -72.88 (s, 3 F, CF3).
ESI-MS: m/z = 560.1 [M+Na]+, 1097.3 [2M+Na]+, 536.1 [M-H]-.
175 ESI-HRMS: m/z calculated for C25H22F3NO7SNa [M+Na]+: 560.0961, found: 560.0961.
176
5.3.4.8 Cbz-4-pinacolboryl-D-β3-hPhg-OBn (62)
Under argon atmosphere, compound 61 (1.68 g, 3.12 mmol, 1.00 eq) was dissolved in degassed dioxane (20.0 mL) and subsequently B2pin2 (948 mg, 3.74 mmol, 1.20 eq), KOAc (925 mg, 9.42 mmol, 3.02 eq), PdCl2(dppf) (228 mg, 312 mol, 0.10 eq) and dppf (173 mg, 132 mol, 0.10 eq) were added. The reaction mixture was stirred at 80°C for 7 h. Then, EtOAc (300 mL) was added to the suspension and the organic phase was washed with saturated aq NaCl solution (3 x 100 mL) and dried over MgSO4. Afterwards, the solvent was removed under reduced pressure. Purification by flash-column chromatography (pentane/EtOAc, 5:1 2:1) gave the pure product 62 (1.55 g, 3.01 mmol, 96%) as a light yellow solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 7.96 (d, 3JHH = 8.6 Hz, 1 H, NH), 7.62 (d,
3JHH = 8.0 Hz, 2 H, aromatic CH), 7.42‒7.15 (m, 12 H, aromatic CH), 5.10‒4.93 (m, 5 H, CH2, -CH), 2.93‒2.73 (m, 2 H, -CH2), 1.29 (s, 12 H, 4 x CH3).
13C-NMR (126 MHz, DMSO-d6): (ppm) = 169.74 (COOBn), 155.19 (Cbz CONH), 145.51, 136.85, 135.86, 134.42, 128.18, 127.75, 127.65, 127.59, 125.82 (aromatic C), 83.49 (C(CH3)2), 65.43, 65.30 (CH2), 51.69 (-C), 40.68 (CH2), 24.54 (C(CH3)2).
ESI-MS: m/z = 516.3 [M+H]+, 538.3 [M+Na]+, 1053.5 [2M+Na]+.
ESI-HRMS: m/z calculated for C30H34BNO6Na [M+Na]+: 538.2377, found: 538.2369.
177 5.3.4.9 Cbz-4-dihydroxyborane-D-β3-hPhg-OBn (63)
Compound 62 (3.74 g, 7.26 mmol, 1.00 eq) was dissolved in acetone (330 mL) and H2O (291 mL). Then, NH4OAc (1.68 g, 21.8 mmol, 3.00 eq) and NaIO4 (4.81 g, 22.5 mmol, 3.10 eq) were added and the reaction mixture was stirred at rt for 2 d. Afterwards, the organic solvent was removed under reduced pressure and the residual aqueous phase was extracted with Et2O (3 x 100 mL). The combined organic phases were washed with saturated aq NaCl solution (100 ml) and dried over MgSO4. The organic solvent was removed in vacuo to provide the final product 63 (2.83 g, 6.54 mmol, 90%) as a white solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 8.06‒7.88 (m, 3 H, NH, aromatic CH), 7.76 (d,
3JHH = 8.0 Hz, 2 H, aromatic CH), 7.41‒7.24 (m, 10 H, aromatic CH), 5.11‒4.89 (m, 5 H, 2 x CH2, -CH), 2.93‒2.73 (m, 2 H, -CH2).
13C-NMR (126 MHz, DMSO-d6): (ppm) = 169.93 (COOBn), 155.29 (Cbz CONH), 144.00, 136.95, 135.93, 134.14, 128.26, 128.23, 127.83, 127.71, 127.66, 125.35 (aromatic C), 65.49, 65.34 (CH2), 51.71 (-C), 40.68 (CH2).
ESI-MS: m/z = 448.2 [M+H]+, 470.2 [M+Na]+, 917.4 [2M+Na]+.
ESI-HRMS: m/z calculated for C24H24BNO6Na [M+Na]+: 470.1750, found: 470.1740.
178
5.3.4.10 Cbz-4-(3,3,5,5-tetramethyl-2,6-dioxopiperazine-1-yl)-D-β3-hPhg-OBn (64)
A suspension of 63 (2.80 g, 6.47 mmol, 1.00 eq), piperazine-2,6-dione 33 (1.10 g, 6.47 mmol, 1.00 eq), Cu(OAc)2 (1.17 g, 6.47 mmol, 1.00 eq), Et3N (1.26 mL, 920 mg, 9.06 mmol, 1.40 eq) and powdered 4 Å molecular sieve (4.00 g) in DMSO (135 mL) was stirred at rt under an oxygen atmosphere for 14 d. Then, the mixture was filtrated over Celite®. The filtrate was mixed with EtOAc (100 mL), H2O (100 mL) and 2 M aq HCl (100 mL) and the phases were separated. The aqueous phase was extracted with EtOAc (3 x 100 mL). The combined organic phases were washed with saturated aq NaCl solution (3 x 100 mL), dried over MgSO4 and the solvent was removed under reduced pressure. Purification by flash-column chromatography (pentane/EtOAc, 1:1 1:3) gave the final product 64 (2.58 g, 4.62 mmol, 71%) as a white solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 7.98 (d, 3JHH = 8.7 Hz, 1 H, NH), 7.41 (d,
3JHH = 8.3 Hz, 2 H, aromatic CH), 7.37‒7.28 (m, 10 H, aromatic CH), 7.05 (d, 3JHH = 8.3 Hz, 2 H, aromatic CH), 5.14‒4.94 (m, 5 H, 2 x CH2, -CH), 2.91‒2.82 (m, 2 H, -CH2), 1.39 (s, 12 H, 2 x CH3).
13C-NMR (126 MHz, DMSO-d6): (ppm) = 176.50 (CONR2), 169.85 (COOBn), 155.26 (Cbz CONH), 141.98, 136.82, 135.87, 134.93, 128.46, 128.25, 128.20, 127.81, 127.72, 127.67,
179 126.70 (aromatic C), 65.54, 65.39 (CH2), 59.61 (C(CH3)2), 51.17 (-C), 40.67 (CH2), 27.95 (C(CH3)2).
ESI-MS: m/z = 558.3 [M+H]+, 580.3 [M+Na]+, 1137.5 [2M+Na]+.
ESI-HRMS: m/z calculated for C32H35N3O6Na [M+Na]+: 580.2418, found: 580.2411.
180
5.3.4.11 Fmoc-4-(3,3,5,5-tetramethyl-2,6-dioxopiperazine-1-yl)-D-β3-hPhg-OH (66)
Amino acid 64 (500 mg, 897 mol, 1.00 eq) was dissolved in MeOH (21.2 mL) and DCM (3.00 mL). Then, Pd(OH)2/C (50% H2O, 101 mg, 717 mol, 0.80 eq) was added and H2
was passed through the suspension at rt for 1 h, and subsequently it was stirred at rt under a H2 atmosphere for 21 h. Afterwards, the suspension was first filtered through a pleated filter and then the filtrate was passed through a micron syringe filter. The solvent was removed under reduced pressure to give the crude unprotected amino acid.
To the crude intermediate NaHCO3 (152 mg, 1.79 mmol, 2.00 eq) and DMF (5.23 mL) were added. Then, Fmoc-OSu (303 mg, 897 mol, 1.00 eq) was added and the reaction mixture was stirred at rt for 20 h. Afterwards, H2O was added to the reaction. The aqueous phase was acidified to pH 2 with 2 M aq HCl and extracted with EtOAc (3 x 50.0 mL). The combined organic phases were washed with saturated aq NaCl solution (50.0 mL), dried over MgSO4 and the solvent was removed under reduced pressure. Purification by flash-column chromatography (DCM/MeOH/AcOH, 100:0:0.1
94:6:0.1) gave the pure product 66 (419 mg, 750 mol, 84%) as a white solid.
1H-NMR (300 MHz, DMSO-d6): (ppm) = 8.00 (d, 3JHH = 8.7 Hz, 1 H, NH), 7.42 (d,
3JHH = 8.4 Hz, 2 H, aromatic CH), 7.39‒7.29 (m, 8 H, aromatic CH), 7.06 (d, 3JHH = 8.4 Hz, 2 H, aromatic CH), 5.08‒4.96 (m, 1 H, CH), 4.32‒4.17 (m, 3 H, CH2,-CH), 2.77‒2.65 (m,
181 2 H, -CH2), 1.41 (s, 12 H, 2 x CH3).
13C-NMR (126 MHz, DMSO-d6): (ppm) = 176.52 (CONR2), 171.54 (COOH), 155.27 (Fmoc CONH), 143.77, 143.73, 142.50, 140.61, 134.78, 128.38, 127.49, 126.98, 126.70, 125.07, 119.97, 119.20 (aromatic C), 65.38 (CH2), 55.31 (C(CH3)2), 51.19 (-C), 46.65 (CH), 40.83 (CH2), 27.96 (C(CH3)2).
ESI-MS: m/z = 556.3 [M+H]+, 578.3 [M+Na]+, 1111.5 [2M+H]+.
ESI-HRMS: m/z calculated for C32H33N3O6Na [M+Na]+: 578.2262, found: 578.2242.
182
5.3.4.12 Fmoc-4-(3,3,5,5-Tetramethyl-2,6-dioxo-4-oxylpiperazine-1-yl)-D-β3 -hPhg-OH (67)
Compound 66 (413 mg, 743 mol, 1.00 eq) was dissolved in DCM (99.0 mL) and the solution was cooled to 0 °C. Then, m-CPBA (70%, 366 mg, 2.12 mmol, 2.00 eq) was added and the resulting reaction mixture was stirred at 0 °C for 15 min followed by stirring at rt for 5 h. The solvent was removed under reduced pressure and the crude product was purified by flash-column chromatography (DCM/MeOH/AcOH, 100:0:0.1
98:2:0.1) to give product 67 (288 mg, 505 mol, 68%) as an orange solid.
ESI-MS: m/z = 571.2 [M+H]+, 588.3 [M+NH4]+, 593.2 [M+Na]+, 1163.4 [2M+Na]+. ESI-HRMS: m/z calculated for C32H32N3O7Na [M+Na]+: 593.2132, found: 593.2130.