Reaction SMILES: [NH:1]([C:13]([O:15][CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[O:14])[C@H:2]([C:10]([OH:12])=[O:11])[CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.[CH3:23]O>CN(C1C=CN=CC=1)C>[NH:1]([C:13]([O:15][CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[O:14])[C@H:2]([C:10]([O:12][CH3:23])=[O:11])[CH2:3][C:4]1[CH:5]=[CH:6][CH:7]=[CH:8][CH:9]=1
Reactant: O=C(N[C@@H](Cc1ccccc1)C(=O)O)OCc1ccccc1
Reactant: CO
Agent: CN(C)c1ccncc1
Product: COC(=O)[C@H](Cc1ccccc1)NC(=O)OCc1ccccc1
Temperature: 4 °C
Reaction time: 12 h

Procedure:
After 1.80 g of Z-Phe was dissolved in 20 mL of MeOH,□73 mg of DMAP and 1.38 g of WSCD HCI were added to the solution at 0° C., followed by stirring at 4° C. for 12 hours. The solvent was concentrated and the concentrate was dissolved in AcOEt. The solution was then washed with 1N HCl aq. solution, satd. NaHCO3 aq. solution and then satd. NaCl aq. solution. After drying over Na2SO4, the solvent was concentrated to give Z-Phe-OMe as oil. After dissolving in 20 mL of dry THF, 196 mg of LiBH4 was added to the solution, followed by stirring at room temperature for 15 hours. The solvent was concentrated and the residue was dissolved in AcOEt and the solution washed with 1N HCl aq. solution, satd. NaHCO3 aq. solution and then satd. NaCl aq. solution. After drying over Na2SO4, the solvent was concentrated and ether-petroleum ether was added to the concentrate to give 1.45 g (yield 85%) of Z-Phe-ol as the precipitate. After 60 mg of 60% NaH was suspended in 10 mL of dry THF, 285 mg of Z-Phe-ol, 264 mg of 18-crown-6 and 1.48 mL of tert-butyl bromoacetate were added to the solution at 0° C. While reverting to room temperature, the mixture was stirred for 15 hours. After the solvent was distilled off in vacuum, the residue was dissolved in AcOEt and the solution washed with 1N HCl aq. solution, satd. NaHCO3 aq. solution and satd. NaCl aq. solution. After drying over Na2SO4, the solvent was concentrated and the concentrate was purified by flash column chromatography to give 217 mg (yield 54%) of Z-PheΨ(CH2O)Gly-OBut as oil. After 160 mg of Z-PheΨ(CH2O)Gly-OBut was dissolved in 20 mL of MeOH, 10% Pd-C was added to the solution, followed by catalytic hydrogenation for 3 hours in a nitrogen flow. The catalyst was removed by filtration and the solvent was concentrated followed by drying. The concentrate was dissolved in 15 mL of DCM, and 114 mg of Fmoc-Cl and 139 μL of DIEA were added to the solution, followed by stirring for 12 hours. After the solvent was distilled off, the residue was dissolved in AcOEt and the solution washed with 1N HCl aq. solution, satd. NaHCO3 aq. solution and then satd. NaCl aq. solution. After drying over Na2SO4, the solvent was concentrated and the concentrate was purified by flash column chromatography. Diethyl ether-petroleum ether was added to give 150 mg (yield 77%) of Fmoc-PheΨ(CH2O)Gly-OBut as the precipitate. To the precipitate, were added 31 mg (15 μmol) of H-LeuArg(Me,Boc2)Trp(Boc2)-Rink amide MBHA resin obtained in a manner similar to the process of EXAMPLE 15, 19 mg of Fmoc-PheΨ(CH2O)Gly-OH (prepared by treating Fmoc-PheΨ(CH2O)Gly-OBut with 50% TFA/DCM for an hour), 180 μL of 0.5M HOAt, 42 mg of PyBrop and 47 μL of DIEA. The mixture was shaken for 18 hours. After the resin washed, 5 mL of 20% piperidine/DMF was added to the resin, followed by stirring at room temperature for 30 minutes. After the resin washed, 9 μL of benzoyl chloride, 13 μL of DIEA and 1 mL of DMF 1 were added to the resin, followed by stirring at room temperature for 2 hours. After the resin washed and dried, 200 μL of TFA/PhSMe/m-cresol/TIS/EDT (85/5/5/2.5/2.5) was added to the resin, followed by stirring for 2 hours. Ether was added to the reaction solution, the resulting precipitate was centrifuged and the supernatant was removed. This procedure was repeated for washing. The residue was extracted with an aqueous acetic acid solution and the extract was filtered to remove the resin. Then, linear density gradient elution (60 minutes) was performed with eluants A/B: 75/25-65/35 using: 0.1% TFA in water and eluant B: 0.1% TFA-containing acetonitrile on preparative HPLC using YMC D-ODS-5-ST S-5 120A column (20×150 mm). The fractions containing the product were collected and lyophilized to give 2.5 mg of white powders.