Supporting Information Novel diphenylmethyl-derived amide protecting group for efficient liquid-phase peptide synthesis; AJIPHASE Daisuke Takahashi*, Tatsuya Yano and Tatsuya Fukui Research Institute For Bioscience Products And Fine Chemicals, Ajinomoto Co., Inc. 1730 Hinaga Yokkaichi, Mie, 510-0885 Japan Corresponding author. Tel.: +81-59-346-0122; fax: +81-59-346-0127; e-mail: daisuke_takahashi@ajinomoto.com Table of content 1. Comparison and examination of the model compounds for anchor support 2. Synthetic scheme of peptide 11 (AAQVLISELAIA-NH 2 ) 3. General information 4. Experimental procedure S1
1. Comparison and examination of the model compounds for anchor support In order to examine the existing anchor support compound 1 1, it was converted to an amine and reacted with an Fmoc-protected amino acid to form a C-terminal amide. Next, removal using TFA to give the corresponding carboxamide was evaluated. Unfortunately, while the anchored amino acid was detached using TFA, the target carboxamide was not observed. Therefore, the structure of the anchor support compound and the appropriate positions at which the long alkoxy chains should be introduced were investigated to identify a compound that can be removed by treatment with TFA. Bz-Phe-OH was employed as the coupling agent for the anchor molecule because it is easily detected by HPLC. It was treated with various types of benzyl amines and diphenylmethylamines bearing methoxy groups, the corresponding compounds were then treated with TFA, and the yield of the recovered, detached Bz-Phe-NH 2 was evaluated. The results are shown in Table S1. As expected, the anchor compounds with methoxy groups in electron-donating positions were more readily detached by TFA; the recovery yield of Bz-Phe-NH 2 was moderate for 2, 4-dimethoxy benzyl amine and good for 2, 4, 6-trimethoxy benzyl amine and 4, 4 -dimethoxy diphenylmethylamine. These results indicated that a long chain alkoxy group should be introduced at the 2-, 4-, and 6-positions in a benzyl-type compound, and at the 4- and 4 -positions in diphenylmethyl (Dpm)-type substrates. Both anchor support compounds 2, 4, 6-trioctadesylbenzylamine and various Dpm derivatives were prepared; however, based on their yields and byproduct formation 2, the Dpm-type anchors were focused in this study. HO OC 18 H 37 OC 18 H 37 OC 18 H 37 1 Table S1. Recovery yield of Bz-Phe-NH 2 for each anchor molecule TFA Bz-Phe-NHR Bz-Phe-NH 2 R Yield(%) OMe OMe OMe OMe OMe OMe MeO OMe 0 0 48 91 21 93 OMe MeO OMe MeO OMe S2
2. Synthetic scheme of peptide 11 (AAQVLISELAIA-NH 2 ) Scheme S1. Synthesis of hydrophobic model peptide 11 (AAQVLISELAIA-NH 2 ) OH NH 2 4 7 Fmoc-Ala-NH 2 cat. MsOH Fmoc-Ala-OH EDC/HOBt Fmoc-Ala NH 5 deprotection Fmoc-AA coupling H-AAQVLISELAIA-NH-Dpm(OC 22 ) yield 83% TFA/H 2 O/TIS final deprotection AAQVLISELAIA-NH 2 11 S3
3. General information: All reagents were purchased and used without further purification. 1 H-NMR and 13 C-NMR spectra were recorded on a 300 MHz spectrometer using CDCl 3 or DMSO-d 6 as the solvent. The chemical shifts (δ) are reported in parts per million (ppm) relative to trace amount of tetramethylsilane (0.00 ppm for 1 H-NMR and 13 C-NMR). The coupling constants (J) are reported in hertz (Hz). High-resolution mass spectra (HRMS) were obtained with a JEOL MS700V (JEOL Datum Ltd.). High-performance liquid chromatography (HPLC) was performed using a SHIMADZU LC20A system (detected at 220 nm), equipped with a C18 reversed-phase column: YMC-Pack ODS-A column 150 mm 4.6 mm ID, (YMC Co., Ltd., Kyoto, Japan). The mobile phase was 0.05 % TFA aq/0.05% TFA acetonitrile = 80:20 to 20:80 in 25 min, and the flow rate was 1.0 ml/min. 4. Experimental procedure The diphenylmethyl-derived anchor compound 4 and 7 were synthesized as follows: Step 1: Synthesis of 4,4 -didocosoxy-benzophenone 3 4,4 -dihydroxy-benzophenone (8.2 g, 38.3 mmol) and 1-bromodocosane (31.3 g, 80.4 mmol) were added DMF (300 ml) and K 2 CO 3 (15.9 g, 115 mmol) and the mixture was stirred at 80 C for 16 h. After completion of the reaction, the reaction mixture was ice-cooled and 1M HCl aq. (300 ml) and water (150 ml) were slowly added with sufficient stirring. The slurry was filtered, and the obtained solid were washed with water and MeOH to give 4, 4 -didocosoxy-benzophenone (30.2 g, 36.4 mmol, 95%). 1 H-NMR (CDCl 3 ) δ 0.89 (6H, t, J=6.6 Hz), 1.13-1.62 (76H, br), 1.81 (4H, m), 4.03 (4H, t, J=6.5 Hz), 6.94 (4H, d, J=8.8 Hz), 7.77 (4H, d, J=8.7 Hz). TOF-MS [M+H] + 831.3 Step 2: Synthesis of bis[4-(docosyloxy)phenyl]methylalcohol 4 To 4, 4 -didocosoxy-benzophenone (28.3 g, 34.1 mmol) were added THF (300 ml) and MeOH (15 ml) and the mixture was heated to 60 C. Sodium borohydride (6.1 g, 161 mmol) was added slowly, and the mixture was stirred at the same temperature for 4 h. The reaction mixture was ice-cooled and 1M HCl aq. (80 ml) was added dropwise. THF was evaporated, water (450 ml) was added and 1M HCl was added to ph 5 7. The slurry was filtered, and the obtained solid were washed with water and MeOH to give 4, 4 -didocosoxybenzhydrol (28.5 g, 34.1 mmol, 99%). 1 H-NMR (CDCl 3 ) δ 0.88 (6H, t, J=6.6 Hz), 1.11-1.61 (76H, br), 1.73 (4H, m), 2.04 (1H, s), 3.93 (4H, t, J=6.6 Hz), 5.76 (1H, s), 6.85 (4H, d, J=8.7 Hz), 7.25 (4H, d, J=8.6 Hz). 13 C-NMR (CDCl 3 ) δ 14.1, 22.7, 26.1, 29.3, 29.4, 29.4, 29.6, 29.6, 29.7, 29.7, 32.0, 68.1, 75.5, 114.4, 127.7, 136.2, 158.6. HRMS (FAB) : Calcd for C 57 H 100 O 3 [M+H] + : 832.7672, Found: 832.7688. Step 3: Synthesis of ethyl [bis-(4-docosoxy-phenyl)-methyl]carbamate 6 To bis-(4-docosoxy-phenyl)-methanol (28.5 g, 34.2 mmol) were added toluene (350 ml), ethyl carbamate (6.1 g, 68.5 mmol) and methanesulfonic acid (0.7 g, 10.3 mmol) and the mixture was S4
stirred at 110 C for 3 h. After stirring, the reaction mixture was cooled to room temperature, Na 2 CO 3 (1.1 g, 8.73 mmol) was added and the solvent was evaporated. The residue was crystallized from MeOH (400 ml) to give ethyl [bis-(4-docosoxy-phenyl)-methyl]carbamate (32.1 g, 33.9 mmol, 99%). 1 H-NMR (CDCl 3 ) δ 0.88 (6H, t, J=6.6 Hz), 1.12-1.60 (79H, br), 1.75 (4H, m), 3.92 (4H, t, J=6.5 Hz), 4.13 (2H, q, J=7.1 Hz), 5.15 (1H, s), 5.85 (1H, d, J=6.9 Hz), 6.83 (4H, d, J=8.6 Hz), 7.13 (4H, d, J=8.6 Hz). TOF-MS [M+Na] + 926.7. Step 4: Synthesis of bis[4-(docosyloxy)phenyl]methylamine 7 To ethyl [bis-(4-docosoxy-phenyl)-methyl]carbamate were added toluene (300 ml), EtOH (200 ml) and NaOH (9.8 g, 245 mmol), and the mixture was refluxed under stirring at 100 C for 16 h. The reaction mixture was cooled to room temperature, and water (300 ml), hexane (200 ml) and EtOAc (200 ml) were added for partitioning. The aqueous layer was discarded, and the organic layer and precipitated solid were washed with water (300 ml 2). The organic layer and solid were recovered. The solvent was evaporated under reduced pressure. To the residue were added water (150 ml) and acetonitrile (150 ml) to allow precipitation. The solid were collected by filtration and thoroughly washed with water and acetonitrile to give bis[4-(docosyloxy)phenyl]methylamine (28.1 g, 33.7 mmol, 98%). 1 H-NMR (CDCl 3 ) δ 0.88 (6H, t, J=6.6 Hz), 1.12-1.62 (78H, br), 1.75 (4H, m), 3.92 (4H, t, J=6.6 Hz), 5.12 (1H, s), 6.83 (4H, d, J=8.6 Hz), 7.24 (4H, d, J=8.6 Hz). 13 C-NMR (CDCl 3 ) δ 14.1, 22.7, 26.1, 29.3, 29.4, 29.4, 29.6, 29.6, 29.7, 29.7, 32.0, 58.5, 68.0, 114.4, 127.8, 138.0, 158.1. HRMS (FAB): Calcd for C 57 H 101 NO 2 [M+H] + : 831.7832, Found: 831.7885 General procedure for the elongation of a peptide chain using the anchor support molecule 7 Step 1: loading of Fmoc-amino acid onto the anchor support compound 7. bis[4-(docosyloxy)phenyl]methylamine 7 (6.0 g, 7.2 mmol) was dissolved in chloroform (80 ml), and then HOBt (1.0 g, 7.2 mmol), Fmoc-Ala-OH H 2 O (2.8 g, 8.6 mmol) and EDC.HCl (1.9 g, 9.5 mmol) were added. The reaction mixture was stirred for 3 h. After the reaction was complete, the solvent was removed under reduced pressure. The obtained residue was precipitated with MeOH (60 ml), and washed with MeCN. The precipitate was dried under reduced pressure to give Fmoc-Ala-NH-Dpm(C22) 5 (8.0 g, 7.1 mmol, 99%). The notation Dpm(C22) indicates the anchor support molecule 7. 1 H-NMR (CDCl 3 ) δ 0.88 (3H, t, J = 6.9 Hz), 1.10-1.50 (76H, br), 1.59 (3H, s), 1.73 (4H, m), 3.82 (2H, t, J = 6.6 Hz), 3.89 (2H, t, J = 6.6 Hz), 4.16 (1H, t, J = 6.9 Hz), 4.30 (4H), 4.41 (1H), 5.38 (1H, br), 6.09 (1H, d, J = 8.1 Hz), 6.62 (1H, br), 6.75 (2H, d, J = 8.7 Hz), 6.81 (2H, d, J = 8.4 Hz), 7.07 (4H), 7.29 (2H), 7.39 (2H, d, J = 7.5 Hz), 7.55 (2H, d, J = 6.9 Hz), 7.76 (2H, d, J = 7.8 Hz). 13 C-NMR (CDCl 3 ) δ 14.1, 22.7, 26.0, 26.1, 29.3, 29.4, 29.6, 29.6, 29.7, 31.9, 47.1, 55.9, 67.2, 68.1, 114.5, 120.0, 125.1, 127.1, 127.8, 128.4, 133.3, 141.3, 143.7, 158.5, 171.0. HRMS (FAB) : Calcd for C 75 H 116 N 2 O 5 [M+H] + : 1124.8884, Found: 1124.9077 Step 2: Elongation of a peptide chain Deprotection and Coupling reactions Fmoc-AA 1 -NH-Dpm(C22) (1.0g) was dissolved in chloroform (10 ml). DBU (1.0 eq) and diethylamine (15 eq) were added dropwise at 0 C. The reaction mixture was stirred at room temperature. After the reaction was complete, the solvent was removed under reduced pressure, S5
and the residue was precipitated with acetonitrile (10 ml). The obtained solid was filtered and dried under reduced pressure to give Fmoc-deprotected H-AA 1 -O-Dpm(C22), which was then dissolved in chloroform (10 ml). HOBt (0.1 eq) and Fmoc-AA 2 -OH (1.1 eq) were added followed by the addition of EDC HCl (1.1 eq) at 0 o C. After the coupling reaction was complete, the solvent was removed under reduced pressure, and the obtained residue was precipitated with MeOH (10 ml). The solid was filtered and dried under reduced pressure to give Fmoc-protected dipeptide Fmoc-AA 2 -AA 1 -NH-Dpm(C22). Elongation of the peptide sequence was performed by repeating this step 2. The crude protected peptide H-Ala-Ala-Gln(Trt)-Val-Leu-Ile-Ser(tBu)-Glu(OtBu)-Leu-Ala-Ile-Ala-NH-Dpm(C22) was synthesized using the procedure described above with 83% yield from 7. HRMS (ESI): Calcd for C 138 H 224 N 14 O 18 [M+H] + : 2366.7121, Found: 2366.7050. Step 3: Final cleavage to obtain a non-protected crude peptide The fully protected peptide on the anchor compound 7 was added to mixed solution of TFA:H 2 O:TIPS = 95:2.5:2.5. Isopropyl ether was poured to reaction mixture and the obtained precipitate was collected by filtration and was dried under vacuum (2 h) to obtain the desired crude peptide acid. The purity of the crude peptide was checked by analytical HPLC using a SHIMADZU LC20A system (220 nm) on a reversed-phase column (YMC-Pack ODS-A, 150 mm 4.6 mm ID). The peptide was eluted with a linear gradient of aqueous acetonitrile/0.05% TFA (20:80 to 80:20 in 25 min.) at a flow rate of 1.0 ml/min. The crude peptide AAQVLISELAIA-NH 2 11 was synthesized using the procedure described above with 90% purity by the HPLC analysis. 1 H-NMR (DMSO-d 6 ) δ 0.72-0.94 (30H) 0.98-1.15 (3H) 1.15-1.29 (10H) 1.33 (3H, d, J = 6.9Hz) 1.38-1.50 (6H, br) 1.57 (2H, m) 1.65-1.80 (4H, br) 1.81-2.02 (3H, m) 2.04-2.17 (2H, br) 2.18-2.32 (2H) 3.85 (1H, br) 4.09-4.60 (12H, m) 6.77 (1H, br) 6.98 (1H, br) 7.24 (2H, br) 7.62 (1H, m) 7.72-7.93 (4H, m) 7.94-8.13 (7H, br) 8.16 (1H, d, J = 7.8Hz) 8.55 (1H, d, J = 7.2Hz) 12.10 (1H, br). HRMS (FAB): Calcd for C 54 H 96 N 14 O 16 [M+H] + : 1197.7207, Found: 1197.7159. Amino acid analysis: Ser 0.98 (1), Gln/Glu 1.95 (2), Ala 4.26 (4), Val 0.90 (1), Leu 1.95 (2), Ile 2.05 (2). Crude linear sequence of peptide 9 (Mpa-Har-Gly-Asp-Trp-Pro-Cys-NH 2 ) was synthesized using the procedure described above with 86% yield (HPLC purity 78%) and was dissolved with 40% MeCN aq. The mixture was neutralized with NH 4 OH to ph 9.0 and was stirred for 2 h at 23 o C. The reaction mixture was acidified with AcOH to ph 4.0 and evaporated. The residual solution was purified by HPLC and Eptifibatide 10 was obtained in 63% yield. The analytical data of the peptide was fully consistent with purchased Eptifibatide (from 2A PharmaChem). 1 H-NMR (DMSO-d 6 ) δ 1.30-1.55 (3H, br) 1.62-2.00 (7H, m) 2.04-2.20 (2H, m) 2.63 (1H, m) 2.78-2.93 (5H, m) 2.93-3.11 (4H, m) 3.48 (1H) 3.81 (1H) 4.32-4.47 (2H, m) 4.51-4.61 (2H, m) 4.25-4.41 (2H, m) 4.55-4.70 (2H, m) 4.67 (1H) 6.88 (2H, s) 6.98 (1H, t, J = 6.6Hz ) 7.05 (1H, t, J = 6.9Hz) 7.15 (1H, s) 7.22 (1H, d, J = 2.1Hz) 7.29 (2H, d, J = 7.8Hz) 7.39 (1H, s) 7.62 (1H, d, J = 7.5Hz) 8.02 (2H, t, J = 7.8Hz) 8.36 (1H, d, J = 9.0Hz) 8.84 (1H) 10.69 (1H, br) 10.83 (1H). TOF-MS [M+H] + 832.2. Isomer of Eptifibatide epimelizing Cys residue was detected only 0.3% (relative retention time (RRT) 1.04) by the HPLC analysis(10-40%). S6
Racemization of Cys residue during loading on to the Dpm-NH 2 -type protecting group was determined 0.4% by HPLC after elongation with Fmoc-Pro-OH and cleavage with TFA as Fmoc-Pro-Cys-NH 2. The HPLC analysis was performed using a SHIMADZU LC20A system (detected at 220 nm), equipped with a C18 reversed-phase column: YMC-Pack ODS-A column 150 mm 4.6 mm ID, (YMC Co., Ltd., Kyoto, Japan). The mobile phase was 0.05 % TFA aq/0.05% TFA acetonitrile-thf = 75:25 to 65:35 in 25 min, and the flow rate was 1.0 ml/min.. The crude peptide AAQVLISELAIA-NH 2 11 synthesis by SPPS The protected peptide H-Ala-Ala-Gln(Trt)-Val-Leu-Ile-Ser(tBu)-Glu(OtBu)-Leu-Ala-Ile-Ala-NH 2 was synthesized with the peptide synthesizer Tribute (Protein technologies, Inc. Tucson, AZ, USA) using Fmoc strategy on a Rink amide resin (0.55 mmol/g, 0.10 g, Watanabe Chemical, Ind. LTD). The following side-chain-protected Fmoc amino acids were employed: Glu(OtBu), Ser(tBu), Gln(Trt). Deprotection of N-Fmoc groups was performed using 20% piperidin (3-5 min x 5). The peptide chain was elongated using FastMoc protocols of coupling with Fmoc-amino acid/hctu/6-cl-hobt/nmm (4/4/4/8 equiv.) in DMF (double coupling, 20 min). The protected peptide resin was treated with TFA:H 2 O:TIPS = 95:2.5:2.5 for 1 h. The resin was filtered and isopropyl ether was poured to the filtrate. The obtained precipitate was collected by filtration and was dried under vacuum (2 h) to give crude peptide AAQVLISELAIA-NH 2. 1. Tamiaki, H.; Obata, T.; Azefu, Y.; Toma, K. Bull. Chem. Soc. Jpn. 2001, 74, 733. 2. An important over-reduced byproduct was observed in low yield during the synthesis of 2, 4, 6-trioctadesylbenzylamine. (Takahashi, D., unpublished result). S7
4,4 -didocosoxy-benzophenone 3 O S8
bis[4-(docosyloxy)phenyl]methylalcohol 4 S9
bis[4-(docosyloxy)phenyl]methylalcohol 4 OH S10
[bis-(4-docosoxy-phenyl)-methyl]carbamate 6 O Et O NH O Et O NH S11
bis[4-(docosyloxy)phenyl]methylamine 7 S12
bis[4-(docosyloxy)phenyl]methylamine 7 NH 2 S13
Fmoc-Ala-NH-Dpm(C22) 5 Fmoc-Ala NH Fmoc-Ala NH S14
Purified Eptifibatide 10 S15
crude peptide AAQVLISELAIA-NH2 11 S16
crude peptide AAQVLISELAIA-NH2 11 S17