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Conformational Analysis of Heteroannularly Substituted Ferrocene Oligoamides
Author(s) -
Lapić Jasmina,
Siebler Daniel,
Heinze Katja,
Rapić Vladimir
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200601230
Subject(s) - chemistry , ferrocene , intramolecular force , steric effects , hydrogen bond , conformational isomerism , stereochemistry , conjugate , nuclear magnetic resonance spectroscopy , amino acid , molecule , organic chemistry , electrochemistry , electrode , mathematical analysis , biochemistry , mathematics
The main conformer of symmetrical conjugates of ferrocene‐1,1′‐dicarboxylic acid with natural amino acids – Fn(CO–AA 1–2 –OMe) 2 (type I, Fn = ferrocene‐1,1′‐diyl, AA = L ‐α‐amino acid) – is supported by two hydrogen bonds between the peptide substituents. To compare intramolecular hydrogen bond patterns of type I conjugates with related asymmetrically substituted derivatives, type II (MeNHCO–Fn–CO–AA–OMe) and type III conjugates (MeNHCO–Fn–CO–AA–NHMe) were prepared in moderate‐to‐good yields in a few steps starting from 1′‐(methoxycarbonyl)ferrocene‐1‐carboxylic acid by using the HOBt/EDC method (AA = Gly, Ala, Val). 1 H NMR spectroscopic variation ratio analysis suggests that an increase in the steric demand of the amino acid side chains favours conformations with hydrogen‐bonded FnCO NH Me groups. CD spectroscopy of chiral derivatives reveals that ( P )‐helical conformations predominate in solution. The experimental findings are in accordance with DFT calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)