Supporting Information Postsynthetic modification of unprotected peptides via S-tritylation reaction Masayoshi Mochizuki, Hajime Hibino and Yuji Nishiuchi *,, SAITO Research Center, Peptide Institute, Inc., Ibaraki, Osaka 567-0085, Japan Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan yuji@peptide.co.jp 1
Contents 1. General Information. 3 a. Materials b. HPLC c. Mass spectrometry and NMR d. Manual solid-phase synthesis (Fmoc-strategy) e. Automated solid-phase synthesis (Boc-strategy) 2. Experimental Section.... 4-19 a. Synthesis of Gly-Cys-Ala-pNA b. Tritylation of Gly-Cys-Ala-pNA. c. Synthesis of Gly-Xaa-Phe-Cys-Gly-NH 2 d. Tritylation of Gly-Xaa-Phe-Cys-Gly-NH 2 e. Synthesis of rat CNP-53 f. Stability of peptide thioester under the tritylation conditions 2
1. General Information.. a. Materials All reagents and solvents were obtained from Peptide Institute, Inc. (Osaka, Japan), Wako Chemical (Osaka, Japan), Tokyo Chemical Industry (Tokyo, Japan) and Watanabe Chemical Industries (Hiroshima, Japan). b. HPLC Analytical HPLC was performed on a Shimadzu liquid chromatograph Model LC-10AT (Kyoto, Japan) with a YMC-ODS AA12S05-1546WT (4.6 x 150 mm) using a flow rate of 1 ml/min at 40 ºC and the following solvent systems: 0.1% TFA in H 2 O (A), 0.1% TFA in CH 3 CN (B). Preparative HPLC was performed on a Shimadzu liquid chromatograph Model LC-8A (Kyoto, Japan) with a YMC-ODS AA12305-2530WT (250 x 30 mm) using a flow rate of 20 ml/min and the following solvent systems: 0.1% TFA in H 2 O (A), 0.1% TFA in CH 3 CN (B). c. Mass spectrometry and NMR Exact mass spectra were measured on an Agilent G1956B LC/MSD detector using an Agilent 1100 series HPLC system. 1 H NMR spectra were recorded on a JEOL-ECX400 spectrometer in dimethyl sulfoxide-d 6 (d 6 -DMSO) with the solvent residual peak (d 6 -DMSO: 1 H = 2.49 ppm) as an internal reference unless otherwise stated. d. Manual solid-phase synthesis (Fmoc-strategy) Starting with Fmoc-NH-SAL-PEG resin, manual peptide chain assembly was carried out using the protocol of 30-min coupling with Fmoc-amino acid/hctu/6-cl-hobt/diea (4/4/4/8 equiv with respect to the peptide resin, 1-min preactivation) in DMF. The following side-chain-protected amino acids were employed: Cys(Ddm), Glu( t Bu), His(MBom), Ser( t Bu), Trp(Boc), Tyr( t Bu). Fmoc deprotection was carried out with 20% piperidine in DMF, followed by washing with DMF (5 x 2 min). 3
e. Automated solid-phase synthesis (Boc-strategy) Automated peptide synthesis was performed on an ABI433A (Forester, CA, USA) peptide synthesizer. The peptide chain was elongated using in situ neutralization protocols of coupling with Boc-amino acid/hctu/6-cl-hobt/diea (4/4/4/6 equiv) in NMP (single coupling, 30 min). The acetyl capping was performed using acetic anhydride/nmp in the presence of DIEA after each coupling step. The following side-chain-protected amino acids were employed: Arg(Tos), Asn(Xan), Asp(OcHex), Cys(MeBzl), Glu(OcHex), His(Bom), Lys(ClZ), Ser(Bzl), Thr(Bzl), Trp(For), Tyr(BrZ). 2. Experimental Section a. Synthesis of Gly-Cys-Ala-pNA Fmoc-Cys(Ddm)-Ala-pNA To a solution of Ala-pNA TosOH (1.00 g, 2.62 mmol), Fmoc-Cys(Ddm)-OH (1.42 g, 2.49 mmol) and HOBt (357 mg, 2.62 mmol) in DMF (8.0 ml) was added EDC (479 μl, 2.62 mmol). The reaction mixture was stirred at room temperature for 2 h. After addition of AcOEt, the organic layers were washed with sat. NaHCO 3, 1N HCl and brine, dried over Na 2 SO 4, filtered and evaporated. The crude residue was precipitated with IPE. The resulting powders were collected by filtration and washed with IPE to yield Fmoc-Cys(Ddm)-Ala-pNA (1.81 g, 96%) as a white powder. 4
Fmoc-Gly-Cys(Ddm)-Ala-pNA To a solution of Fmoc-Cys(Ddm)-Ala-pNA (1.70 g, 2.23 mmol) in DMF (10 ml) was added dimethylethylamine (2.40 ml, 22.3 mmol). The mixture was stirred at room temperature for 1.5 h and evaporated in vacuo. The resulting residue was used for the next step without further purification. To a solution of the product, Boc-Gly (410 mg, 2.34 mmol) and HOBt (316 mg, 2.34 mmol) in DMF (10 ml) was added DIC (363 μl, 2.34 mmol). The reaction mixture was stirred at room temperature for 5 h. After addition of AcOEt, the organic layers were washed with sat. NaHCO 3, 1N HCl and brine, dried over Na 2 SO 4, filtered and evaporated. The residue was precipitated with IPE and the resulting powders were collected by filtration and washed with IPE to yield Boc-Gly-Cys(Ddm)-Ala-pNA (1.47 g, 95%) as a white powder. Gly-Cys-Ala-pNA (1) Boc-Gly-Cys(Ddm)-Ala-pNA (1.40 g, 2.00 mmol) was treated with TFA/TIS/H 2 O = 95/5/5 (12 ml) for 1 h. After TFA was evaporated, the residue was precipitated with ether. The resulting powders were collected by filtration and washed with ether. The product was purified by preparative HPLC (8-35% CH 3 CN/0.1% TFA for 80 min) to give Gly-Cys-Ala-pNA (747 mg, 80%); 1 H NMR (d 6 -DMSO) δ = 8.61 (2H, d, J = 8.24 Hz), 8.58 (2H, d, J = 6.40 Hz), 8.22-8.18 (2H, m), 7.96 (3H, m), 7.83-7.79 (2H, m), 4.57-4.52 (1H, m), 4.40-4.37 (1H, m), 3.60 (2H, m), 2.84-2.68 (2H, m), 2.30 (1H, t, J = 8.24 Hz), 1.33 (3H, d, J = 7.32 Hz m); LRMS (ESI) m/z calcd for C 27 H 33 N 7 O 5 S 5
([M+H] + ) 370.11, found 370.1. b. Tritylation of GCA-pNA To a solution of 10 mm GCA-pNA in HFIP or TFA was added Trt-OH (1.1 or 3.0 equiv). The reaction mixture was stirred at room temperature for 1 h and analyzed by HPLC. Table S1. Tritylation of Gly-Cys-Ala-pNA entry solvent Trt-OH GCA-pNA GC(Trt)A-pNA (equiv) (area% 340 nm) (area% 340 nm) 1 HFIP 1.1 1.6 96.6 2 HFIP 3.0 0.2 98.0 3 TFA 1.1 33.4 61.4 4 TFA 3.0 6.0 87.7 Figure S1. Tritylation of GCA-pNA (1) (1 h). HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-80% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 340 nm. 6
c. Synthesis of Gly-Xxx-Phe-Cys-Gly-NH 2 H-Gly-Trp-Phe-Cys-Gly-NH 2 (3a) This peptide was prepared from Fmoc-NH-SAL resin (510 mg, 0.23 mmol) according to the general manual SPPS procedure. The peptide resin was treated by TFA/TIS/H 2 O (v/v/v, 95/5/5) at room temperature for 1 h to give a crude product, which was purified by preparative HPLC to obtain 69.7 mg (45%). Analytical HPLC: R t, 10.8 min (10-98% CH 3 CN/0.1% TFA for 25 min, 220 nm); LRMS (ESI) m/z calcd for C 27 H 33 N 7 O 5 S ([M+H] + ) 568.23, found 568.2. H-Gly-Tyr-Phe-Cys-Gly-NH 2 (3b) This peptide was prepared from Fmoc-NH-SAL resin (510 mg, 0.23 mmol) as described above for H-Gly-Trp-Phe-Cys-Gly-NH 2 (3a) to yield 73.2 mg (50%). Analytical HPLC: R t, 8.7 min (10-98% CH 3 CN/0.1% TFA for 25 min, 220 nm); LRMS (ESI) m/z calcd for C 25 H 32 N 6 O 6 S ([M+H] + ) 545.21, found 545.2. H-Gly-Ser-Phe-Cys-Gly-NH 2 (3c) This peptide was prepared from Fmoc-NH-SAL resin (510 mg, 0.23 mmol) as described above for H-Gly-Trp-Phe-Cys-Gly-NH 2 (3a) to yield 65.0 mg (50%). Analytical HPLC: R t, 6.7 min (10-98% CH 3 CN/0.1% TFA in 25 min, 220 nm); LRMS (ESI) m/z calcd for C 19 H 28 N 6 O 6 S ([M+H] + ) 469.18, found 469.2. H-Gly-His-Phe-Cys-Gly-NH 2 (3d) This peptide was prepared from Fmoc-NH-SAL resin (510 mg, 0.23 mmol) according to the general manual SPPS procedure. The peptide resin was treated by TFA/TIS/H 2 O (v/v/v, 95/5/5) in the presence of MeONH 2 HCl (5 equiv) at room temperature for 1 h to give a crude product, which was purified by preparative HPLC to obtain 60.8 mg (37%). Analytical HPLC: R t, 5.8 min (10-98% CH 3 CN/0.1% TFA for 25 min, 220 nm); LRMS (ESI) m/z calcd for C 22 H 30- N 8 O 5 S ([M+H] + ) 519.21, found 519.2. H-Gly-Glu-Phe-Cys-Gly-NH 2 (3e) This peptide was prepared from Fmoc-NH-SAL resin (310 mg, 0.14 mmol) as described 7
above for H-Gly-Trp-Phe-Cys-Gly-NH 2 (3a) to yield 31.5 mg (37%). Analytical HPLC: R t, 7.0 min (10-98% CH 3 CN/0.1% TFA for 25 min, 220 nm); LRMS (ESI) m/z calcd for C 21 H 30- N 6 O 7 S ([M+H] + ) 511.19, found 511.1. H-Gly-Met-Phe-Cys-Gly-NH 2 (3f) This peptide was prepared from Fmoc-NH-SAL resin (310 mg, 0.14 mmol/g) as described above for H-Gly-Trp-Phe-Cys-Gly-NH 2 (3a) to yield 34.1 mg (40%). Analytical HPLC: R t, 9.1 min (10-98% CH 3 CN/0.1% TFA for 25 min, 220 nm); LRMS (ESI) m/z calcd for CH 30- N 6 O 7 S ([M+H] + ) 513.19, found 513.2. d. Tritylation of GXFCG-NH 2 To a solution of 10 mm GXFCG-NH 2 in HFIP or TFA was added Trt-OH (1.1 or 3.0 equiv). The reaction mixture was stirred at room temperature for 1 h and analyzed by HPLC. Table S2. Tritylation of Gly-Xaa-Phe-Cys-Gly-NH 2 entry Xaa solvent GXFCG-NH 2 Trt-OH GXFC(Trt)G-NH 2 GX(Trt)FC(Trt)G-NH 2 (area% (equiv) (area% 220nm) (area% 220nm) 220nm) 1 Trp HFIP 1.1 1.2 96.2 1.0 2 Trp TFA 1.1 26.9 66.6 0.8 3 Trp TFA 3.0 25.7 73.6 0.7 4 Tyr HFIP 1.1 0.7 97.5 - a 5 Tyr TFA 1.1 14.7 78.1-6 Tyr TFA 3.0 9.64 90.4-7 Ser HFIP 1.1 1.0 96.3-8 Ser TFA 1.1 10.1 80.8-9 Ser TFA 3.0 0.5 91.6-10 His HFIP 1.1 2.1 94.2 2.4 8
11 His TFA 1.1 10.1 83.9-12 His TFA 3.0 4.9 91.3-13 Glu HFIP 1.1 2.0 96.0-14 Glu TFA 1.1 8.3 86.1-15 Glu TFA 3.0 9.1 86.6-16 Met HFIP 1.1 0.2 97.9-17 Met TFA 1.1 8.9 86.6-18 Met TFA 3.0 3.0 90.1 - a -: not detectable. Figure S2, Tritylation of GWFCG-NH 2 (3a). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 equiv)/tfa. (C) Trt-OH (3.0 equiv)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 9
Figure S3. Tritylation of GYFCG-NH 2 (3b). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 equiv)/tfa. (C) Trt-OH (3.0 eq.)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. Figure S4. Tritylation of GSFCG-NH 2 (3c). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 equiv)/tfa. (C) Trt-OH (3.0 equiv)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 10
Figure S5. Tritylation of GHFCG-NH 2 (3d). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 eq. equiv)/tfa. (C) Trt-OH (3.0 equiv)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. Figure S6. Tritylation of GEFCG-NH 2 (3e). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 equiv)/tfa. (C) Trt-OH (3.0 equiv)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 11
Figure S7. Tritylation of GMFCG-NH 2 (3f). (A) Trt-OH (1.1 equiv)/hfip. (B) Trt-OH (1.1 equiv)/tfa. (C) Trt-OH (3.0 equiv)/tfa. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. e. Synthesis of rat CNP-53 (1-21)-MPA-Leu-NH 2 (DLRVDTKSRAAWARLLHEHPN-MPA-Leu-NH 2 ) (5) The peptide was assembled using an ABI 433A peptide synthesizer on a Boc-Asn(Xan)-MPA-Leu-MBHA resin (1.0 g, 0.47 mmol) according to the general automated SPPS procedure. The peptide resin was treated by HF/p-cresol/butanedithiol (v/v/v, 80/5/15) in the presence of MeONH 2 HCl (5 equiv) at -2 C to -5 ºC for 1 h to give a crude product, which was purified by preparative HPLC to obtain 0.17 g (10%). Analytical HPLC: Rt, 16.5 min (1-60% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI): calcd 2686.1, found 2686.2. [Thz 22 ]-(22-34)-MPA-(Arg) 3 -NH 2 (ThzRKYKGGNKKGLSKG-MPA-RRR-NH 2 ) (6) The peptide was assembled using an ABI 433A peptide synthesizer on a Boc-Gly-MPA-Leu-MBHA resin (0.86 g, 0.50 mmol) according to the general automated SPPS procedure. The peptide resin was treated by HF/p-cresol (v/v, 80/20) at -2 C to -5 ºC for 1 h to give a crude product, which was purified by preparative HPLC to obtain 0.62 g (39%). Analytical HPLC: Rt, 9.6 min (1-60% CH 3 CN/0.1% TFA for 12
25min, 220 nm); LRMS (ESI): calcd 2192.6, found 2192.4. (37-53) (CFGLKLDRIGSMSGLGC) (7) The peptide was assembled using an ABI 433A peptide synthesizer on a Boc-Cys(MeBzl)-PAM resin (0.80 g, 0.50 mmol) according to the general automated SPPS procedure. The peptide resin was treated by HF/p-cresol (v/v, 80/20) at -2 C to -5 ºC for 1 h to give a crude product, which was purified by preparative HPLC to obtain 0.32 g (31%). Analytical HPLC: Rt, 17.4 min (1-60% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd for C 75 H 125 N 21 O 23 S 3 ([M+H] + ) 1756.8, found 1756.8. [Thz 22 ]-(22-53) (8) [Thz 22 ]-(22-34)-MPA-(Arg) 3 -NH 2 (6) (283 mg, 89.4 umol) and (36-52) (7) (186.7 mg 91.2 umol) were dissolved in freshly degassed 0.2 M sodium phosphate buffer (ph 8.0, ml) containing 6 M guanidine hydrochloride. To the solution, 2% thiophenol (v/v) was added, and the whole mixture was allowed to react under stirring for 4 h at room temperature and then treated with DTT (30.8 mg, 200 μmol). After 20 min the ph was adjusted to < 3 by adding AcOH. The mixture was washed with ether and the aqueous layers were directly subjected to preparative HPLC to obtain 0.33 g (86%). Analytical HPLC: R t, 15.6 min (1-60% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 3372.7, found 3374.1. 13
[Thz 22, Cys(Trt) 37,53 ]-(22-53) (9) To a solution of [Thz 22 ]-(22-53) (8) (87.6 mg, 20.2 mmol) in HFIP (1.3 ml) was added Trt-OH (21 mg, 80.8 mmol). The reaction mixture was stirred at 4 ºC for 2 h. The product was precipitated with IPE, and collected by filtration and washed with IPE to give the title compound (82.8 mg, 87%). Analytical HPLC: Rt, 17.6 min (10-80% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 3859.6, found 3859.0. Figure S8. Tritylation of [Thz 22 ]-(22-53) (8). (A) [Thz 22 ]-(22-53) (8). (B) reaction mixture, 2 h. (C) purified product. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-80% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 14
Figure S9. ESI MS profiles of [Thz 22, Cys(Trt) 37,53 ]-(22-53) (9). Increasing the fragmentor voltage led to an increase in the rate of de-tritylation. 15
[Cys 22,Cys(Trt) 37,53 ]-(22-53) (10) [Thz 22,Cys(Trt) 37,53 ]-(22-53) (9) (80 mg, 16.9 μmol) was dissolved in degassed 0.5 M MeONH 2 HCl containing 3 M guanidine hydrochloride. The mixture was stirred at room temperature for 4 h. The reaction mixture was directly subjected to preparative HPLC to obtain the title compound (75.3 mg, 94%). Analytical HPLC: Rt, 17.6 min (10-80% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 3847.6, found 3847.0. [Cys 22,Cys(Trt) 37,53 ]-(1-53) (11) [Cys 22, Cys(Trt) 37,53 ]-(22-53) (10) (24.0 mg, 5.08 μmol) and (1-21)-MPA-Leu-NH 2 (5) (20.6 mg, 6.10 μmol) were dissolved in freshly degassed 0.2 M sodium phosphate buffer (ph 8.0, 2.0 ml) containing 20 mm TCEP, 30 mm MPAA and 6 M guanidine hydrochloride. The mixture was allowed to react under stirring for 20 h at room 16
temperature and then treated with DTT (10.0 mg, 64.9 μmol). After 20 min the ph was adjusted to < 3 by the addition of AcOH. The reaction mixture was directly subjected to preparative HPLC to obtain 35.4 mg (91%). Analytical HPLC: Rt, 16.1 min (10-80% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 6315.4, found 6315.0. [Cys(Trt) 37,53 ]-(1-53) (12) To a solution of [Cys 22,Cys(Trt) 37,53 ]-(1-53) (11) (25.0 mg, 3.21 umol) in degassed 0.2M sodium phosphate buffer (ph 5.8) containing 3 M guanidine hydrochloride and 0.4 M TCEP was added 1 M VA-044 (64.2 μl) and GSH (39.4 mg, 128 μmol). The mixture was stirred at 40ºC for 4 h and then directly subjected to preparative HPLC to obtain the title compound (23.1 mg, 93%). Analytical HPLC: Rt, 16.1 min (10-80% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 6283.3, found 6283.3. Figure S10. Desulfurization of [Cys 22,Cys(Trt) 37,53 ]-(1-53) (11) (reaction mixture, 3 h). HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-80% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 17
rat CNP-53 To a solution of [Cys(Trt) 37,53 ]-(1-53) (12) (12.8 mg, 1.65 μmol) in 5%TFA/HFIP was added TIS (3.4 ul, 16.5 μmol). The mixture was stirred at room temperature for 20 min and then diluted with H 2 O and AcOH. After 0.1 M I 2 /MeOH (16.5 ul) was added dropwise, the reaction was quenched by adding 1 M ascorbic acid (16.5 ul). The mixture was directly subjected to preparative HPLC to obtain the title compound (7.3 mg, 61%). Analytical HPLC: Rt, 16.5 min (1-60% CH 3 CN/0.1% TFA for 25min, 220 nm); LRMS (ESI) calcd 5796.7, found 5796.3. 18
Figure S11. HPLC and ESI-MS of rat CNP-53. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 1-60% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. f. Stability of peptide thioester under the tritylation conditions Figure S12. Stability of S-1 under the tritylation conditions. (A) S-1. (B) reaction mixture, 1 h. (C) reaction mixture, 2 h. No decomposition of the thioester moiety was observed during the tritylation reaction performed in HFIP. HPLC conditions: column, YMC-Pak ODS (4.6 x 150 mm); elution, 10-98% CH 3 CN in 0.1% TFA (25 min) at 40 C; flow rate, 1.0 ml/min; detection, 220 nm. 19