A systematic study of the solid state and solution phase conformational preferences of β-peptides derived from transpentacin

The solid state and solution phase conformational preferences of a homologous series of β-peptides derived from (S,S)-2-aminocyclopentanecarboxylic acid (transpentacin) have been investigated using a variety of spectroscopic and crystallographic techniques. These studies indicate that the hexamer and pentamer persist as a 12-helix in both the solid state and solution phase. Although the conformational traits of a 12-helix are exhibited by oligomers with as few as three residues in the solid state, in solution the trimer exists as an equilibrium of many alternative conformers whilst the tetramer has been shown to predominantly exist in either a 12-helix or a turn-type conformation.

The hexamer and pentamer derived from (S,S)-2-aminocyclopentanecarboxylic acid (transpentacin) each persist as a 12-helix in both the solid state and solution phase. Although the conformational traits of a 12-helix are exhibited by oligomers with as few as three residues in the solid state, in solution the trimer exists as an equilibrium of many alternative conformers whilst the tetramer has been shown to predominantly exist in either a 12-helix or a turn-type conformation.Figure optionsDownload as PowerPoint slide

tert-Butyl (S,S)-2-aminocyclopentanecarboxylateC10H19NO2[α]D23=+59.4 (c 1.1 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

tert-Butyl (S,S)-2-[N-(benzyloxycarbonyl)amino]cyclopentanecarboxylateC18H25NO4[α]D23=+34.9 (c 1.0 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

(S,S)-2-[N-(Benzyloxycarbonyl)amino]cyclopentanecarboxylic acidC14H17NO4[α]D18=+23.5 (c 1.3 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

Cbz-[(S,S)-ACPC]2-OtBuC24H34N2O5[α]D23=+39.0 (c 1.1 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S)

H-[(S,S)-ACPC]2-OtBuC16H28N2O3[α]D23=+50.1 (c 0.8 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S)

Cbz-[(S,S)-ACPC]2-OHC20H26N2O5[α]D18=+28.6 (c 1.6 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S)

Cbz-[(S,S)-ACPC]3-OtBuC30H43N3O6[α]D23=+46.6 (c 1.0 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S)

Cbz-[(S,S)-ACPC]4-OtBuC36H52N4O7[α]D23=+45.2 (c 0.6 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S)

H-[(S,S)-ACPC]3-OtBuC22H37N3O4[α]D23=+46.4 (c 0.9 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S)

H-[(S,S)-ACPC]4-OtBuC28H46N4O5[α]D23=+59.7 (c 0.6 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S)

Cbz-[(S,S)-ACPC]5-OtBuC42H61N5O8[α]D23=+53.8 (c 0.3 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S,S,S)

Cbz-[(S,S)-ACPC]6-OtBuC48H70N6O9[α]D20=+49.2 (c 0.2 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S,S,S,S,S)

Boc-[(S,S)-ACPC]2-OtBuC21H36N2O5[α]D18=+33.1 (c 0.7 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S)

Boc-[(S,S)-ACPC]3-OtBuC27H45N3O6[α]D23=+36.2 (c 0.5 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S)

Boc-[(S,S)-ACPC]4-OtBuC33H54N4O7[α]D23=+48.7 (c 0.4 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S)

Boc-[(S,S)-ACPC]5-OtBuC39H63N5O8[α]D23=+45.8 (c 0.6 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S,S,S)

Boc-[(S,S)-ACPC]6-OtBuC45H72N6O9[α]D20=+48.7 (c 1.1 in CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S,S,S,S,S,S,S)

Cbz-[(S,S)-ACPC]3-OHC26H35N3O6[α]D23=+29.1 (c 0.3 in MeOH)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S,S,S,S,S)