原创：对肿瘤、恶性疟原虫和锥虫病等疾病的高净值药物分子“达托里昔布”的合成工艺改进
达托里昔布是一种作用于PI3K和mTOR的双激酶抑制剂，该化合物及其类似物在针对肿瘤、恶性疟原虫和锥虫病等疾病有着来突出的药物活性。针对该类化合物的放量合成研究工作也一直在进行当中，为该类化合物的药物方向研究提供者技术支持。
原初合成路线的研究
于达托里昔布的合成工作，最初相关文献的报道当中使用的合成路线为：首先使用三氯氧磷(POCl3)对化合物1的羟基进行定位氯化得到化合物2，随后在醋酸溶剂中，引入苯胺化合物3，进行C-N偶联，得到化合物4。随后在用雷尼镍还原化合物4的硝基，转化为氨基，得到化合物5。之后化合物5和双光气反应，得到脲类化合物6。
随后氢化钠对二级氨位置去质子化，再引入碘甲烷发生SN2反应完成氨基位点的甲基化(化合物7)。最后再通过Suzuki偶联反应，将化合物7的溴代位点进行芳香化修饰，得到终产物化合物9(达托里昔布)。该合成路线具有较高的原子经济性，全程避免了保护基的使用。但在该合成路线中，比较具有挑战性的问题在于：如何纯化溶解度较低的终产物9，同时降低最后偶联步钯催化剂的残留；以及在反应过程中避免有毒有害试剂的使用，比如二氯甲烷和双光气等。
中间体7的合成改良
我们在这里提出了一个针对关键中间体7的改进型合成路线，其实原料的选择依然是化合物1，氯代反应后不经提纯，去除溶剂后直接投入到乙腈当中，发生胺化反应，得到化合物4。之后采用一锅法，先在四氢呋喃溶剂中是用雷尼镍还原硝基，之后不经提纯，直接加入N,N’-羰基二咪唑试剂作为羰基供体发生缩合反应，以78%产率(从化合物4出发)得到化合物6。针对后续的氨基甲基化，我们也做了改进，在第一代路线中，使用的时氰化钠作为去质子化用途的碱，在这里我们为了放量考虑，使用了THF中可溶的叔丁醇钾作为去质子化的碱，并且选用了不易挥发的硫酸二甲酯或碳酸二甲酯作为甲基化试剂。但是需要指出的是，甲基化试剂依然是致癌物。
终产物9的Suzuki偶联工艺改进和重结晶提纯工艺研究
在最后的偶联反应当中，作者经过一系列的配体和金属催化剂比例筛选，最后确定了选用二(三苯基膦)氯化钯和三苯基膦作为催化剂组合的方式，选用KHCO3作碱，DMF/水作为混合溶剂，进行反应。在反应过后，以醋酸和水作为溶剂，对粗产物9进行重结晶操作，并且在随后的过程中使用离子交换剂SMOPEX234和碳粉去除残存的钯催化剂，最后得到纯净的达托里昔布。
Experimental Section
General
All solvents and reagents used were of bulk quality.
The NMR spectra were recorded on a Bruker Avance 400 (1H NMR: 400 MHz; 13C NMR: 100 MHz) spectrometer in the indicated solvent. Coupling constants (J) are reported in hertz (Hz). The accuracy of the measurement of the coupling constants was within ±0.2 Hz.
HPLC was performed on an Agilent 1100 or 1200 machine. High-resolution liquid chromatography mass spectrometry (HR-LC/MS) measurements were performed on a Waters Acquity UPLC/Synapt G2 Q-TOF MS instrument using electrospray ionization in the positive ion mode after separation by liquid chromatography (Nexera from Shimadzu). The elemental composition was derived from the mass spectra acquired at a high resolution of approximately 30 000 on an LTQ Orbitrap XL mass spectrometer (Thermo Scientific). A high mass accuracy below 1 ppm was obtained using a lock mass.
All reactions were carried out under an inert atmosphere (N2).
Synthesis of 2[4-(6-Bromo-3-nitro-quinolin-4-yl amino)-phenyl]-2-methyl-propionitrile (4)
6-Bromo-4-hydroxy-3-nitroquinoline (78.5 kg; 292 mol) was placed in a reactor together with toluene (463 kg) at RT. Then, tripropylamine (62.7 kg; 438 mol; 1.5 equiv) was added. The suspension was then heated to 80 °C, and POCl3 (89.4 kg; 584 mol; 2 equiv) was added within approximately 1 h. The addition tank was rinsed with 17.5 kg toluene. The reaction mixture was heated to 90 °C and stirred at 90–95 °C for 2 h, and the turnover of the reaction was checked by HPLC (requirement: <1% starting material). The reaction mixture was cooled to 65–70 °C, and 345 kg of toluene was distilled off. Then, four times toluene (262 kg) was added, and the same amount of toluene was distilled off. The solvent was exchanged to acetonitrile. Four times acetonitrile (235 kg) was added, and the same amount of the solvent was distilled off. Finally, acetonitrile (628 kg) was added. The internal temperature was decreased to 25 °C, and a solution of 2-(4-amino-phenyl)-2-methyl propionitrile (3) (49 kg; 306 mol; 1.05 equiv) in 78.5 kg of acetonitrile was added within 1.5 h. The addition tank was rinsed with 14 kg acetonitrile. During the addition of starting material 3, product 4 precipitates from the reaction mixture. The reaction mixture was stirred at RT for 18 h. The reaction was checked with HPLC (requirement: <1.0 area % intermediate 2). Finally, H2O (3000 kg) was added, and 1268 kg of the solvent was distilled off under vacuum at 70 °C. After distillation of the first 700 L of the solvent, additional H2O (900 kg) was added. When the distillation was stopped, the pH was adjusted to 5–6 by adding 15% NaOH (187 kg). The reaction mixture was then cooled to 0 °C within 4.5 h and stirred at that temperature for 2 h; product 4 was finally isolated via filtration. The filter cake was washed with acetonitrile/H2O = 1:10 (240 kg). The wet product was dried at 60 °C in vacuum to give 115.4 kg of product 4, which corresponded to a 96% yield. The purity of the production batches was in the range from 90 to 98% (HPLC area %). This product was used in the next step without further purification.
1H NMR (400 MHz, dimethyl sulfoxide (DMSO)-d6) δ 10.15 (s, 1H), 9.07 (s, 1H), 8.71 (d, J = 1.9 Hz, 1H), 7.98 (dd, J = 8.9, 1.9 Hz, 1H), 7.91 (d, J = 8.9 Hz, 1H), 7.47 (d, J = 8.6 Hz, 2H), 7.14 (d, J = 8.6 Hz, 2H), 1.68 (s, 6H).
13C NMR (101 MHz, DMSO-d6) δ 148.17, 147.72, 141.40, 140.59, 137.92, 135.58, 132.08, 130.19, 127.23, 126.49, 125.12, 123.02, 120.48, 120.42, 36.71, 28.77.
HR-LC MS: m/z [M + H]+ calcd for C19H16N4O2Br: 411.0457; found: 411.0350.
Synthesis of 2-[4-(8-Bromo-2-oxo-2,3-dihydro-1H-imidazo[4,5-c]quinolin-1-yl)-phenyl]-2-methyl-propionitrile (6)
Starting product 4 (113.9 kg, 277 mol) and Na2CO3 (5.7 kg) were combined with THF (1481 kg) into an autoclave. The Raney nickel catalyst (21 kg) was added, and the mixture was hydrogenated under normal pressure of molecular hydrogen up to the uptake of 3 equiv of H2(usually, approximately 8–10 h). At this point, no significant consumption of H2 was observed. The turnover of the reaction was checked by HPLC (<1% of intermediate 4). The catalyst was then filtered off and washed four times with THF (122 kg). THF was distilled off under vacuum (1400 kg). Then, twice THF (473 kg) was added and distilled off. More THF (1416 kg) was added, and the H2O content was measured (limit: 1000 ppm; KF-titration). Finally, carbonyldiimidazole (86 kg, 530 mol; 1.9 equiv) was added. The reaction mixture was heated to 60 °C within 1.5 h and was stirred at this temperature for 3 h. The reaction was checked by HPLC for completion (<1% of intermediate 5; HPLC area %), and the suspension was cooled to 0–5 °C within 3 h and stirred for another 2 h; then, the crude product was filtered. The filter cake was washed with THF (471 kg). The crude THF-wet product was charged into a reactor together with H2O (439 kg) and suspended at IT 40–50 °C for 1 h. Then, the product was filtered, washed with H2O, and dried at 90 °C until the H2O content (KF) was <0.4% to obtain 88 kg of intermediate 6 (78% yield). The purity of the isolated product was in the range from 92 to 97% (HPLC area %) of the production batches.
1H NMR (400 MHz, DMSO-d6) δ 11.82 (s, 1H), 8.80 (s, 1H), 7.94 (d, J = 9.1 Hz, 1H), 7.89–7.80 (m, 2H), 7.75–7.67 (m, 2H), 7.65 (dd, J = 9.1, 2.1 Hz, 1H), 6.97 (d, J = 2.1 Hz, 1H), 1.82 (s, 6H).
13C NMR (101 MHz, DMSO-d6) δ 153.88, 143.76, 143.08, 135.16, 134.90, 132.86, 129.94, 129.91, 129.12, 127.25, 124.83, 122.80, 122.60, 119.30, 116.43, 37.32, 28.83.
HR-LC MS: m/z [M + H]+ calcd for C20H16N4OBr: 407.0507; found 407.0530.
Intermediate 5 could be isolated after hydrogenation by evaporation of THF and crystallization from n-heptane. Analytical results of intermediate 5:
1H NMR (500 MHz, DMSO-d6; 100 °C) δ 8.67 (s, 1H), 7.95–7.85 (m, 1H), 7.79 (d, J = 8.8 Hz, 1H), 7.64 (s, 1H), 7.49–7.36 (m, 1H), 7.31–7.22 (m, 2H), 6.68–6.53 (m, 2H), 5.15 (br. s, 2H), 1.65 (s, 6H).
13C NMR (126 MHz, DMSO-d6; 100 °C) δ 144.18, 143.97, 140.56, 137.30, 130.70, 130.65, 127.75, 126.43, 125.17, 124.26, 123.09, 121.48, 119.02, 113.83, 35.20, 28.00.
HR-LC MS: m/z [M + H]+ calcd for C19H18N4Br: 381.0715; found 381.0746.
Synthesis of 2-(4-((3-Aminoquinolin-4-yl)amino)phenyl)-2-methylpropanenitrile (10)
Intermediate 5 (5 g; 13.1 mmol) was dissolved in 100 mL of 2-Me-THF together with 2 g (19.8 mmol; 1.5 equiv) of triethylamine. Then, 0.5 g of Pd/C (10%) catalyst was added, and the mixture was hydrogenated in an autoclave at RT with 1 bar overpressure for a total of 8 h. An LC/MS check of the reaction mixture showed complete consumption of starting material 5. The catalyst was filtered off and washed with 2-Me-THF, and the 2-Me-THF product solution was washed with 50 mL of 0.05 M citric acid, followed by two washes with 50 mL deionized H2O. The 2-Me-THF solution of compound 10 was evaporated to dryness to obtain 3.5 g of product 10 as a brown evaporation residue (88% yield).
Analytical Results of Compound 10
1H NMR (400 MHz, DMSO-d6) δ 8.63 (s, 1H), 7.96–7.79 (m, 2H), 7.73–7.62 (m, 1H), 7.43–7.30 (m, 2H), 7.30–7.19 (m, 2H), 6.62–6.50 (m, 2H), 5.31 (br.s, 2H), 1.61 (s, 6H).
13C NMR (101 MHz, DMSO-d6) δ 144.91, 143.99, 142.20, 137.31, 130.33, 129.04, 126.54, 126.10, 125.77, 125.11, 124.13, 122.68, 121.68, 114.00, 35.64, 28.41.
HR-LC MS: m/z [M + H]+ calcd for C19H19N4: 303.16042, found: 303.16068.
Synthesis of 2[4-(8-Bromo-3-methyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-c]quinolin-1-yl)-phenyl]2-methyl-propionitrile (7)
Intermediate 6 (166 kg; 408 mol) was placed together with THF (889 kg) in a reactor. Then, a solution of 20% m/m KOtBu (343 kg; 611 mol; 1.5 equiv) in THF was added within 2–3 h under cooling at 20–25 °C. The addition tank was rinsed with THF (45 kg). The mixture was stirred at 20–25 °C for 0.5 h, and dimethyl sulfate (77 kg; 610 mol; 1.5 equiv) was added within 2.5 h. The reaction mixture was stirred for 2 h at 25 °–30 °C. Then, the reaction was checked with HPLC (requirement <2% of 6). A solution of 5% NH3 in H2O (316.5 kg) was added, and the mixture was stirred for 0.5 h at 25–30 °C. Product 7 was filtered and washed with THF (182 kg) followed by a mixture of methanol (93 kg) and H2O (93 kg). The crude wet product was charged in a reactor together with DMF (1717 kg) and activated charcoal (8.6 kg). The mixture was heated at 120 °C within 2.5 h and stirred at that temperature for 0.5 h. Then, the charcoal was filtered off and rinsed with DMF (345 kg). The filtrate was cooled within 5 h to 5 °C and stirred at that temperature for 1.5 h; then, the product was filtered and washed with TBME (452 kg). The product was dried in vacuum at 45 °C to obtain 133.8 kg of product 7 (78% yield). The purity level of the 9 production batches: > 99.0% (area % HPLC); impurity 12 < 0.2% (area % HPLC).
1H NMR (400 MHz, acetic acid-d4) δ 9.20 (s, 1H), 8.22 (d, J = 9.2 Hz, 1H), 8.02–7.88 (m, 2H), 7.81 (dd, J = 9.2, 2.0 Hz, 1H), 7.73 (d, J = 8.6 Hz, 2H), 7.23 (d, J = 2.0 Hz, 1H), 3.76 (s, 3H), 1.90 (s, 6H).
13C NMR (101 MHz, acetic acid-d4) δ 154.10, 144.79, 140.04, 133.67, 132.19, 130.97, 130.94, 129.25, 128.17, 127.10, 123.87, 123.67, 123.10, 120.87, 115.63, 37.24, 28.27, 27.71.
HR-LC MS: m/z [M + H]+ calcd for C21H18N4OBr: 421.0664; found 421.0636.
Analytical Data of Compound 12
1H NMR (400 MHz, CDCl3) δ 7.82–7.71 (m, 2H), 7.53–7.47 (m, 3H), 7.31 (d, J = 9.1 Hz, 1H), 6.88 (d, J = 2.2 Hz, 1H), 3.86 (s, 3H), 3.79 (s, 3H), 1.85 (s, 6H).
13C NMR (101 MHz, CDCl3) δ 153.76, 153.71, 143.58, 136.00, 134.34, 130.99, 129.14, 126.96, 126.03, 124.18, 123.86, 116.97, 115.43, 115.12, 112.92, 37.36, 29.76, 29.49, 29.29.
HR-LC MS: m/z [M + H]+ calcd for C22H20N4O2Br: 451.07642; found 451.07642.
Synthesis of 2-methyl-2-[4-[3-methyl-2-oxo-8-(quinolin-3-yl)-2,3-dihydro-1H-imidazo[4,5-c]quinolin-1-yl]-phenyl] propionitrile (crude 9; pure 9)
Intermediate 7 (155 kg; 368 mol) was placed in a reactor together with DMF (961 kg) at RT under N2. The mixture was degassed by evacuating and flushing several times with N2. Then, bis(triphenylphosphine) palladium dichloride (0.78 kg; 1.1 mol; 0.3 mol %) and triphenylphosphine (0.62 kg; 2.4 mol; 0.64 mol %) were added. In a second reactor, 3-quinoline boronic acid 8 (70 kg; 405 mol; 1.1 equiv) was dissolved in DMF (721 kg) at 60 °C. A solution of KHCO3 (207 kg) in H2O (1033 kg) was added at 60 °C, and the solution of 8 was degassed. Meanwhile, the first reactor was heated to 95–100 °C, and the hot solution of 8 was added within 1.5 h at >95 °C to the starting material 7. The reaction mixture was stirred for 2– 6 h at this temperature and was checked by HPLC (requirement: <2% 7; area %). A solution of l-cysteine (13.7 kg) in demineralized H2O (115 kg) was added within 20 min. The mixture was stirred at >95 °C for 0.5−1 h. Then, demineralized H2O (712 kg) was added. The mixture was cooled within 9 h to 0 °C and was stirred at that temperature for 4 h. The product crude 9 was filtered and washed with H2O (2296 kg) to obtain 209 kg wet crude 9 (theoretical 100% yield: 172 kg), which was directly converted to the product pure 9.
This crude product contained 151 ppm Pd and <1 ppm Ni (after drying in the lab). The HPLC purity of this intermediate crude 9 was 98.8% (area % HPLC).
Acetic acid (1634 kg) was placed in a reactor together with the above crude product (209 kg). Then, Smopex-234 (17.5 kg) was added. The mixture was stirred at RT for 2 h and charcoal (17.5 kg) was added, followed by AcOH (204 kg). The mixture was heated to 90 °C within 1.5 h and stirred at that temperature for 1 h. Then, charcoal and Smopex-234 were filtered off and washed with AcOH (369 kg). To the filtrate, Smopex-234 (17.5 kg) followed by charcoal (17.5 kg) and AcOH (89 kg) was added. The mixture was stirred for 1 h at 90 °C. Then, Smopex-234 and charcoal were removed by filtration. The filter cake was washed with AcOH (553 kg). AcOH was distilled off under vacuum at 70 °C to a residual volume of approximately 950 L in the vessel (measured by radar). Then, demineralized H2O (2888 kg) was added at 80–90 °C. The mixture was seeded (0.5 kg of pure 9). Stirring was continued for 0.5 h; the mixture was cooled within 7–10 h to 0 °C and stirred at that temperature for 4 h; then, the product pure 9 was filtered and washed with a mixture of demineralized H2O (368 kg) and AcOH (128 kg) followed by demineralized H2O (2943 kg). The wet product (253 kg) was dried in a paddle dryer at 80 °C under full vacuum (<10 mbar) to obtain 152.2 kg of purified product pure 9 (88% yield; based on intermediate 7). The product contained <1 ppm Pd and <1 ppm Ni. HPLC purity, 99.8 area %. Assay AcOH <1% m/m.
1H NMR (400 MHz, acetic acid-d4) δ 9.14 (s, 1H), 8.82 (d, J = 2.3 Hz, 1H), 8.39 (d, J = 9.0 Hz, 1H), 8.23 (d, J = 2.0 Hz, 1H), 8.14–8.04 (m, 2H), 7.93–7.97 (m, 3H), 7.89–7.82 (m, 2H), 7.79 (ddd, J = 8.4, 7.0, 1.3 Hz, 1H), 7.72–7.62 (m, 1H), 7.36 (d, J = 1.8 Hz, 1H), 3.79 (s, 3H), 1.81 (s, 6H).
13C NMR (101 MHz, acetic acid-d4) δ 154.12, 147.17, 144.83, 144.78, 139.98, 135.59, 135.40, 133.84, 132.65, 131.96, 131.19, 130.04, 129.38, 128.54, 128.39, 128.03, 127.77, 127.17, 126.62, 126.40, 123.74, 123.71, 118.99, 114.57, 37.32, 28.31, 27.81.
Anal. calcd for C30H23N5O: C, 76.74; H, 4.94; N, 14.92. Found: C, 76.34; H, 4.92; N, 14.82.
HR-LC MS: m/z [M + H]+ calcd for C30H24N5O: 470.1981; found 470.2009.
Analytical Data of Compound 11
1H NMR (400 MHz, acetic acid-d4) δ 9.32 (s, 1H), 8.42 (d, J = 8.7 Hz, 1H), 7.96–7.89 (m, 2H), 7.86 (ddd, J = 8.5, 7.0, 1.1 Hz, 1H), 7.81–7.71 (m, 2H), 7.57–7.48 (m, 1H), 7.36 (d, J = 8.4 Hz, 1H), 3.78 (s, 3H), 1.89 (s, 6H).
13C NMR (101 MHz, acetic acid-d4) δ 154.34, 144.62, 138.79, 134.50, 133.73, 130.77, 129.12, 128.27, 127.88, 127.16, 123.94, 123.73, 123.45, 121.09, 114.24, 37.16, 28.13, 27.86.
HR-LC MS: m/z [M + H]+ calcd for C21H19N4O: 343.15534; found: 343.15552.
文献来源：OPRD：Development of a Robust Synthesis of Dactolisib on a Commercial Manufacturing Scale
DOI: 10.1021/acs.oprd.9b00221