Addition of a peptide fragment on an alpha-helical depsipeptide induces alpha/3(10)-conjugated helix: synthesis, crystal structure, and CD spectra of Boc-Leu-Leu-Ala-(Leu-Leu-Lac)3-Leu-Leu-OEt.
The depsipeptide Boc(1)-Leu(2)-Leu(3)-Ala(4)-Leu(5)-Leu(6)-Lac(7)-Leu(8)-Leu(9)-Lac(10)-Leu(11)-Leu(12)-Lac(13)-Leu(14)-Leu(15)-OEt(16) (1) (Boc = tert-butyloxycarbonyl, Lac = L-lactic acid residue) has been synthesized from the peptide Boc-Leu-Leu-Ala-OEt (2) and a depsipeptide, Boc-(Leu-Leu-Lac)(3)-Leu-Leu-OEt (3). Single crystals of 1 were successfully obtained and the structure has been solved by direct methods (such as Sir2002 and Shake-and-Bake). Interestingly, 1 adopts an alpha/3(10)-conjugated helix containing a kink at the junction of peptide and depsipeptide segments, Leu3-Lac7. This is significantly different from the conformation of 3, which has a straight alpha-helical structure with standard phi and psi angles. Microcrystalline CD spectra were also studied to compare structural properties of 1 and 3. The differences between alpha/3(10)- and alpha-helices appear in these CD spectra.
Oku
Hiroyuki
H
Department of Chemistry, Gunma University, Kiryu, Gunma 376-8515, Japan.
Ohyama
Takafumi
T
Hiroki
Akihiro
A
Yamada
Keiichi
K
Fukuyama
Keiichi
K
Kawaguchi
Hiroyuki
H
Katakai
Ryoichi
R
D002942:Circular Dichroism / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods; D047630:Depsipeptides / Q000737:chemistry*; D004151:Dipeptides / Q000138:chemical synthesis*; D006860:Hydrogen Bonding; D007930:Leucine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D010446:Peptide Fragments / Q000138:chemical synthesis* / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011522:Protons; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared
D047630:Depsipeptides; D004151:Dipeptides; D009842:Oligopeptides; D010446:Peptide Fragments; D011522:Protons; D012996:Solutions; C038361:leucylleucine; D007930:Leucine