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Synthesis of three 11 C‐labelled methionine‐containing enkephal in analogues
Author(s) -
Någren Kjell,
Ragnarsson Ulf,
Långström Bengt
Publication year - 1988
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580250206
Subject(s) - chemistry , methyl iodide , pentapeptide repeat , reagent , sodium iodide , yield (engineering) , alkylation , iodide , liquid ammonia , methionine , peptide synthesis , chemical synthesis , peptide , ammonia , stereochemistry , organic chemistry , amino acid , in vitro , catalysis , biochemistry , materials science , metallurgy
The synthesis of three S‐[methyl‐ 11 C]‐labelled enkephal in analogues, iyr‐D‐Ala‐Gly‐Phe‐Met‐NH 2 , Tyr‐D‐Ala‐D‐Ala‐Phe‐Met‐NH 2 and Tyr‐D‐Met‐Gly‐Phe‐Pro‐NH 2 , from the corresponding S‐benzyl‐homocysteine‐containing peptides is reported. The protected pentapeptide amides were prepared by (3+2) fragment condensations in solution. These peptides were subsequently deprotected with sodium in liquid ammonia and the sulphide anions formed alkylated with [ 11 C]‐methyl iodide to give the S‐[methyl‐ 11 C]‐labelled enkephalins. After purification by preparative LC, these labelled peptides were obtained in 55 to 75 % radiochemical yield, decay corrected, based on the [ 11 C]methyl iodide produced, within 30‐40 min from start of the synthesis of this reagent. The radiochemical purities of the products were higher than 98 %, and the specific activity was in the order of 20‐200 mCi/μmol.