Oligomers of cis-β-norbornene amino acid: Formation of β-strand mimetics

Abstract

The oligomers of constrained cis-exo-beta-norbornene amino acid were synthesised and characterised by extensive NMR, CD, IR and MD studies. The results showed the formation of both right and left handed consecutive 6-membered hydrogen-bonded strands for [2S,3R] and [2R,3S] enantiomers, respectively.

Differentiation of Positional Isomers of Hybrid Peptides Containing Repeats of β-Nucleoside Derived Amino Acid (β-Nda-) and L-Amino Acids by Positive and Negative Ion Electrospray Ionization Tandem Mass Spectrometry (ESI-MSn)

“…The positive ion ESI mass spectra of all these peptides (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) + ions (Scheme 2). Fragmentation of these peptides can be explained by using the nomenclature, which was originally proposed for α-peptides by Roepstorff and Fohlman, and later modified by Biemann [18][19][20].…”

“…Fragmentation of these peptides can be explained by using the nomenclature, which was originally proposed for α-peptides by Roepstorff and Fohlman, and later modified by Biemann [18][19][20]. The negative ion ESI mass spectra of these peptide acids (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) + ion in 2 can also be explained by an another mechanism involving 1,5-H migration from the tert-butyl group to the -NH-leading to the concomitant loss of CO 2 and C 4 H 8 (Scheme 3).This process may not be possible for 1 due to the N-terminal β-Nda. + precursor ions.…”

“…The oligomers of these amino acids both in cisand trans-conformation have exhibited diverse helical patterns in solution [12][13][14]. The fundamental structural element in proteins is the β-strand, which is known to be conformationally suitable for specific recognition by bimolecular receptors such as proteolytic enzymes, major histocompatibility complex (MHC) proteins and transferases [12][13][14][15][16][17].…”

<strong>Synthesis of novel </strong>(&plusmn;)-<strong><em>cis-exo</em></strong><strong>-norbornane amino acid containing cyclic hexapeptide: Analogue of Dolastatin 16 </strong>

“…Norbornadiene was converted in to strained unusual amino acid and oligomerized to obtain hetero-oligomers with other unusual amino acids. 16,17 The unusual norbornane amino acid was synthesized as reported in the literature using commercially available norbornene. [16][17][18][19][20] The synthesis was performed in two pathways: (i) synthesis of dimers and tetramer (ii) synthesis of hexamer followed by Yamaguchi macrocyclization.…”

“…16,17 The unusual norbornane amino acid was synthesized as reported in the literature using commercially available norbornene. [16][17][18][19][20] The synthesis was performed in two pathways: (i) synthesis of dimers and tetramer (ii) synthesis of hexamer followed by Yamaguchi macrocyclization. [21][22][23] (S)-Phenylalanine amine salt (1) in DCM solution is neutralized with TEA at 0°C to get (S)-methyl 2-amino-3-phenyl propionate (2).…”