Dimethyl Sulfide → HDTrp-Leu-MetNH2 trifluoroacetate

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Reaction Steps

Condensation of BocDTrpOPFP (4.70 g.) and HLeu-MetNH2 hydrochloride salt (Example 1, 2.98 g.) by the activated ester method using ethyldiisopropylamine gave BocDTrp-Leu-MetNH2 in 71% yield. De-t-butoxycarbonylation of BocDTrp-Leu-MetNH2 using trifluoroacetic acid, methyl sulfide, and ethanedithiol gave HDTrp-Leu-MetNH2 trifluoroacetate salt in 100% yield. Condensation of BocD,LBpaOH (2.95 g.) and HDTrp-Leu-MetNH2 trifluoroacetate salt (3.79 g.) by the mixed anhydride method using diphenylphosphinyl chloride and separation of the diastereoisomers by column chromatography on silica gel using chloroform-methanol (91:9) as eluant gave BocLBpa-DTrp-Leu-MetNH2 and BocDBpa-DTrp-Leu-MetNH2 each in 19% yield. De-t-butoxycarbonylation of BocLBpa-DTrp-Leu-MetNH2 (0.875 g.) and BocLBpa-DTrp-Leu-MetNH2 (0.875 g.) using trifluroracetic acid in methyl ethyl sulfide and ethanedithiol gave HLBpa-DTrp-Leu-MetNH2 and HDBpa-DTrp-Leu-MetNH2, both as the trifluoroacetate salts and both in 100% yield.

Provenance & Evidence