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Organometallic Half‐Sandwich Complexes Promote the Formation of Linear Oligopeptides from Amino Acid Esters
Author(s) -
Robl Christian,
Maurus Michael,
Sünkel Karlheinz,
Beck Wolfgang,
Krämer Roland,
Polborn K.
Publication year - 1996
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19960021208
Subject(s) - tripeptide , dipeptide , chemistry , tetrapeptide , amino acid , stereochemistry , peptide , racemization , yield (engineering) , oligopeptide , ruthenium , medicinal chemistry , organic chemistry , catalysis , biochemistry , materials science , metallurgy
Organometallic dipeptide ester complexes of the general formula [(L)M(Cl)( K 2 ‐NH 2 CH 2 CONCH 2 CO 2 R)] ( 1 : LCp*, MRh, 2 : LCp*, MIr, 3 : Lη 6 ‐C 6 Me 6 , MRu) react smoothly with various α‐L‐amino acid esters in the presence of NEt 3 to yield the tripeptide ester complexes [(L)M(Cl)( K 2 ‐NH 2 CHR'CONCH 2 CONHCH 2 CO 2 R)] ( 5–7 ). In the same fashion chloro K 2 ‐tetrapeptide ester complexes 10 and 11 are obtained either from tripeptide ester complexes or by subsequent addition of two equivalents of amino acid ester to a dipeptide ester complex. When the strong base NaOMe is used in the reaction of the diglycine ester compounds with amino acid esters. K 3 ‐tripeptide ester complexes 12 and 13 are produced, in which one of the two coordinated peptide nitrogen atoms is pyramidal. The hexamethylbenzene ruthenium complexes 13 with tripeptide ligands are formed with very high diastereoselectivity. A plausible reaction mechanism for the metal‐promoted peptide synthesis is presented. Synthesis and isolation of the peptide esters proceeds without racemization.