Lawesson's reagent → tert-butyl (S)-2-phenyl-1-thiocarbamoylethylcarbamate

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Reaction Steps

After 264 mg of Boc-Phe-NH2 was dissolved in 20 mL of THF, 1.62 g of Lawesson's reagent was added to the solution, followed by stirring for 24 hours. Insoluble matters were removed by filtration, the solvent was concentrated and the concentrate was dissolved in AcOEt. The solution was washed with satd. NaHCO3 aq. solution and then satd. NaCl aq. solution. After drying over Na2SO4, the solvent was concentrated and the concentrate was purified by flush column chromatography. Diethyl ether-petroleum ether was added to give 275 mg (yield 98%) of (S)-2-tert−Butoxycarbonylamino-3-phenylpropanethioamide (Boc-PheΨ(CSNH)—NH2) as precipitates. After 42 mg of the peptide was treated at 0° C. with 9.7 N HCl to remove Boc, the removal of Fmoc with 10% DEA/DMF treatment followed by condensation by the PyBOP/HOBt method were repeated to give 66 mg of Fmoc-LeuArg(Pbf)PheΨ(CSNH)—NH2 (yield 93%). To 17 mg of Boc-Tyr(But)Asn(Trt)Trp(Boc)Asn(Trt)Ser(But)PheGly-OH (SEQ ID NO: 215) prepared as in EXAMPLE 2, H-LeuArg(Pbf)PheΨ(CSNH)—NH2 (prepared by treating 14 mg of Fmoc-LeuArg(Pbf)PheΨ(CSNH)—NH2 with 10% DEA/DMF), 9 mg of PyBrop, 3 mg of HOAt and 7 mL of DIEA were added and the mixture was stirred for 15 hours. After the solvent was concentrated, chloroform-diethyl ether was added thereto for precipitation. To 10 mg of the product, 100 μL of TFA/PhSMe/m-cresol/TIS/EDT (85/5/5/2.5/2.5) was added and the mixture was stirred for 2 hours. Diethyl 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 (30 minutes) was performed with eluants A/B:72/28-62/38 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 1.0 mg of white powders.

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