Beta-peptide

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β-alanine, an example of a β amino acid. The amino group attaches not to the α carbon but to the β carbon, which in this case is a methylene group.

Beta-peptides (β-peptides) are peptides derived from β-amino acids, in which the

β-carbon (i.e. the carbon two atoms away from the carboxylate group). The parent β-amino acid is β-alanine (H2NCH2CH2CO2H), a common natural substance, but most examples feature substituents in place of one or more C-H bonds. β-peptides usually do not occur in nature. β-peptide-based antibiotics are being explored as ways of evading antibiotic resistance.[1] Early studies in this field were published in 1996 by the group of Dieter Seebach[1] and that of Samuel Gellman.[2]

Structure

As there are two carbons available for substitution, β-amino acids have four sites (chirality included; as opposed to two in α-amino acids) for attaching the organic residue group.[3] Accordingly, two main types β-amino acids exist differing by which carbon the residue is attached to: ones with the organic residue (R) next to the amine are called β3 and those with position next to the carbonyl group are called β2. A β-peptide can consist of only one kind of these amino acids (β2-peptides and β3-peptides), or have a combination of the two. Furthermore, a β-amino acid can form a ring using both of its sites and also be incorporated into a peptide.[3]

Synthesis

β-Amino acids have been prepared by many routes,

Arndt-Eistert synthesis
.

Secondary structure

Because their backbones are longer than those of normal

gauche conformation
about the bond between the α-carbon and β-carbon. This also affects the thermodynamic stability of the structure.

Many types of helix structures consisting of β-peptides have been reported. These conformation types are distinguished by the number of atoms in the hydrogen-bonded ring that is formed in solution; 8-helix, 10-helix, 12-helix, 14-helix,[6] and 10/12-helix have been reported. Generally speaking, β-peptides form a more stable helix than α-peptides.[7]

Clinical potential

β-peptides are stable against proteolytic degradation in vitro and in vivo, a potential advantage over natural peptides.[8] β-Peptides have been used to mimic natural peptide-based antibiotics such as magainins, which are highly potent but difficult to use as drugs because they are degraded by proteolytic enzymes.[9]

Examples

β-amino acids with a wide variety of substituents exist. Named by analogy to the biological

β-lysine, β-arginine, β-glutamate, β-glutamine, β-phenylalanine and β-tyrosine.[10]: 23  Of these, β-alanine is found in mammals and incorporated in pantothenic acid, an essential nutrient.[10]: 2  Two α-amino acids are also structurally β-amino acids: aspartic acid and asparagine.[10]: 218  Microcystins are a class of compounds containing a β-isoaspartyl (i.e. aspartic acid linked with its beta-carboxyl) residue.[10]
: 23 

See also

References

  1. ^
    doi:10.1002/hlca.19960790402
    .
  2. doi:10.1021/ja963290l
    .
  3. ^
    doi:10.1039/a704933a
    .
  4. PMID 16292808
    .
  5. PMID 16173757
    .
  6. S2CID 205497333. Archived
    from the original on 2022-02-13. Retrieved 2022-05-07.
  7. S2CID 247917035
    .
  8. S2CID 35579693
    .
  9. PMID 12071741
    .
  10. ^
    OCLC 559972352. Archived
    from the original on 7 May 2022. Retrieved 7 May 2022.
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