Transesterification of peptide esters and peptidyl resins in methanol-containing calcium acetate.
The following crude peptide derivatives obtained by thermolysin catalysis in the presence of calcium acetate, were dissolved in methanol and in methanol-containing calcium acetate to determine the possible occurrence of transesterification: Z-Asn-Leu-Gly-OEt, Boc-Asn-Leu-Gly-OEt, Moz-Asn-Leu-Gly-OBzl, Moz-Asn-Leu-Gly-OtBu, Moz-Gln-Leu-Gly-OEt, Moz-Asn-Ile-Gly-OEt, and Moz-Asn-Leu-Ala-OEt. Only Z-Asn-Leu-Gly-OEt and Moz-Gln-Leu-Gly-OEt were transesterified in methanol, indicating the existence of a peptide derivative-Ca2+ catalytic complex that may favor the reaction. In the presence of calcium acetate, all protected peptide esters except the t-butyl esters were transesterified. The transesterification of several other di- and tripeptide derivatives of different structures in methanol-containing calcium acetate was detected by HPLC and confirmed by the isolation and characterization of some of the protected peptide methyl esters obtained. Boc-Leu-Gly- and Moz-Asn-Leu-Gly-Merrifield resin were also transesterified in these solutions.
Department of Biochemistry, University of São Paulo, Brazil.
M T
MT
Miranda
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Theobaldo
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Tominaga
D000085:Acetates / Q000737:chemistry*; D019342:Acetic Acid; D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D004951:Esterification; D000432:Methanol / Q000737:chemistry*; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis*; D012116:Resins, Plant / Q000737:chemistry*
D000085:Acetates; D010455:Peptides; D012116:Resins, Plant; D019342:Acetic Acid; D000432:Methanol