Synthesis and Structural Characterization of Homochiral Homo‐oligomers of Parent cis‐ and trans‐Furanoid‐β‐Amino Acids

Abstract

The synthesis of homochiral homo-oligomers of cis- and trans-3-aminotetrahydrofuran-2-carboxylic acids (parent cis- and trans-furanoid-β-amino acids, referred to as "cis-/trans-FAA") has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left-handed helicity. The cis-FAA homo-oligomers show a 14-helix structure, in contrast to the homo-oligomers of cis-ACPC, which adopt a sheet like structure. The trans-FAA homo-oligomers were found to adopt a 12-helix structure, the same trend found in trans-ACPC homo-oligomers. With the help of ab initio calculations, the structural features of cis-ACPC and cis-FAA hexamers were compared. We believe that the more compact packing of the cis-FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen.

C-3 epimers of sugar amino acids as foldameric building blocks: improved synthesis, useful derivatives, coupling strategies

“…With detailed experimental studies on various fully protected 3-Osulfonyl-furanoses we have established optimum conditions forming key intermediates and derivatives. As described recently (Pandey 2011;Giri 2012), newly synthesized sugar amino acid derivatives including the herein reported Fmoc-X-, key reactions and intermediates of the sterically hindered secondary amines were probed to make successfully -Aaa-tX-Aaa-and -Aaa-tX-tX-Aaatype "inserts" for α/β-chimera peptides. Thus, we have shown that both C-3 epimers of 3-azido-3-deoxy-pentofuranuronic acid, N 3 -RibAFU(ip)-OH (6) and N 3 -XylAFU(ip)-OH (7) are suitable building blocks to be inserted into β/β-oligopeptides.…”

“…Foldamer synthesis with sterically hindered amines is a challenge and thus, preliminary reaction in optimizing conditions for making short sequences from β-amino acids is a requirement: dimeric, tetrameric and hexameric units form some of them were already studied (Chandrasekhar 2004;Chandrasekhar 2005;Jagannadh 2006;Pandey 2011;Giri 2012). Here we present the synthesis of Nterminal "masked", C-terminal protected -X-X-type β-dipeptide, by coupling N-methylated 3-amino-3-deoxy-ribofuranuronamide (28) with the related 3-azido-3-deoxy-ribofuranuronic acid (6, Scheme 8).…”

Origin of problems related to Staudinger reduction in carbopeptoid syntheses

“…Recently, sugar amino acids (SAA), par-ticularly, fiveor six-membered cyclic amino sugar carbox-ylic acids, appeared as appropriate building blocks for car-bopeptoid foldamers (Herradón and Seebach 1989;Kessler et al 1995;Long et al 1999;Simone et al 2005;Sharma et al 2008Sharma et al , 2011Andreini et al 2009). Numerous furanoid and pyranoid carbohydrate analogs of trans-2-aminocyclo-pentane carboxylic acid (trans-ACPC) and trans-2-amino-cyclohexane carboxylic acid (trans-ACHC) were synthe-sized and built into homo-and heterooligomers to test their self-assembling abilities (Pandey et al 2011;Giri et al 2012;Risseeuw et al 2013).…”

Synthesis and Structural Characterization of Homochiral Homo‐Oligomers of cis‐γ‐Methoxy‐Substituted cis‐ and trans‐Furanoid‐β‐Amino Acids

“…[3,4] Figure 1 provides the secondary structures of some homo-oligomers of β-FAAs. [5] The homo-oligomers of two diastereomeric FAAs have been shown to have distinct lefthanded helicity, in which cis-FAA oligomers VI are characterized by the presence of a 14-helix structure, which is in contrast to the cis-ACPC homo-oligomers II [6] that adopt nary investigation of their solution secondary structures revealed that they are the same as the homo-oligomers of the parent cis-/trans-FAA with the methoxy group only being a spectator substituent. As expected, the folding propensity of the homo-oligomers is not comparable to each other.…”