Incorporation of the Unnatural Organometallic Amino Acid 1′‐Aminoferrocene‐1‐carboxylic Acid (Fca) into Oligopeptides by a Combination of Fmoc and Boc Solid‐Phase Synthetic Methods

Abstract

The organometallic amino acid 1′‐aminoferrocene‐1‐carboxylic acid (Fca) was incorporated internally into a peptide sequence by solid‐phase methods combining natural Fmoc‐protected amino acids and Boc‐Fca‐OH to give the pentapeptide Boc‐Fca‐Ala‐Gly‐Val‐Leu‐NH2 (2) and the octapeptide Ac‐Val‐Gly‐Ala‐Fca‐Ala‐Gly‐Val‐Leu‐NH2 (3). Compound 3 was found to have a helically ordered structure by NMR and CD spectroscopy, which is stabilized by intramolecular hydrogen bonding in an antiparallel β‐sheet‐like arrangement. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

“…On the other hand mechanical changes are expected to change conductivity in these foldamers. [61] Redoxdriven folding/unfolding of these and larger oligoferrocene amides prepared by solid-phase peptide synthesis [16,17,54] will be exploited in further studies.…”

Synthesis and structure of N-substituted (1-ferrocenylethyl)amine derivatives

“…For amide (8) and carbamic ester (6) three intensity control reflections measured every 120 min did not show any significant loss of intensity during the data collections, which were performed on an Enraf Nonius CAD4 diffractometer, using the graphite monochromated CuK α radiation (λ = 1.54179 Å) at the room temperature [295(2)] K. The WinGX [12] standard procedure was applied for the data reduction. The structures were solved with SIR97 [13], and refined with the SHELXL97 [14] using the full matrix least squares refinement.…”

“…Natural peptide turns, however, will always result in anti-parallel peptide strands. This feature was realized in conjugates II-AA which are unlike previous metallocene turn structures truly organometallic turn mimetics [7][8][9]. Recently we submitted the synthesis of the first heteroannularly substituted ferrocene amino acid derivatives containing chiral center (Fcca, III, n = 0) [10] (Scheme 1).…”

Solid‐Phase Synthesis of Transition‐Metal Complexes

“…One Fca unit has been appended to a tetrapeptide to give the pentapeptide Boc-FcaAla-Gly-Val-Leu-NH 2 (52 a) and incorporated internally into the octapeptide Ac-Val-Gly-Ala-Fca-Ala-Gly-Val-Leu-NH 2 (52 b) by using Fmoc-protected a-amino acids, BocFca-H (49 b) and a TentaGel resin with a base-labile HMB linker [6] (Scheme 22; HMB = hydroxymethylbenzoyl). [88] Two ferrocene units have been linked together on solid support (TentaGel resin with an acid-labile Wang linker [6] ) by using Fmoc-protected a-amino acids and Fmoc-Fca-H (49 a) giving the tripeptide Ac-Fca-Fca-Ala-OH (Scheme 23, 53). [89] In a fully analogous fashion the tripeptides with one internal Fca unit Ac-Ala-Fca-Gly-OH (54 a), Ac-Ala-FcaAla-OH (54 b) and Ac-Gly-Fca-Phe-OH (54 c) were prepared by using Fmoc protecting groups on TentaGel-Wang resin.…”