Angewandte
Chemie
3
h
JN,C’ scalar coupling through the hydrogen bond in an
A. M. Gronenborn, A. Bax, J. Am. Chem. Soc. 1999, 121, 6275;
c) M. Barfield, J. Am. Chem. Soc. 2002, 124, 4158; d) A. Bagno,
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V. A. Likic, F. G. Prendergast, S. Macura, J. Am. Chem. Soc.
H(N)CO-type experiment. Interestingly, in MeOH, a solvent
compatible with peptide helical structures, this phenomenon
is clearly seen with peptides I, II, III and V, but not with
peptide IV, most probably because the labeled carbonyl
residue (Gly) in the latter is quite flexible and located at
the beginning of the main chain (N-terminal fraying). Of the
five peptides, only pentapeptide IV does not bear a con-
formationally restricted C -tetrasubstituted a-amino acid at
the N-terminus. This study is the first successful application of
this novel and important NMR spectroscopic methodology to
2002, 124, 14221; h) C. M. Bougault, M. K. Eidgness, J. H.
Prestegard, Biochemistry 2003, 42, 4357; i) W. D. Arnold, E.
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Markwick, R. Sprangers, M. Sattler, J. Am. Chem. Soc. 2003,
a
125, 644; k) T. Tuttle, J. Gräfenstein, A. Wu, E. Kraka, D.
Cremer, J. Phys. Chem. B 2004, 108, 1115; l) G. Gemmecker,
Angew. Chem. 2000, 112, 1276; Angew. Chem. Int. Ed. 2000, 39,
1224.
310
-helical peptides. It is also noteworthy that in peptide III
1
5
13
the N– C’ scalar coupling between the (i) (aMe)Val
carbonyl carbon atom and the (i + 4) (aMe)Val amide
nitrogen atom is not seen, allowing us to conclude that the
a-helical structure is essentially absent in this hexapeptide.
This finding demonstrates the power of this technique to
discriminate between the two most relevant helical structures
[3] R. Anders, O. Ohlenschläger, V. Soskic, H. Wenschuh, B. Heise,
L. R. Brown, Eur. J. Biochem. 2000, 267, 1784.
4] A. Liu, W. Hu, S. Qamar, A. Majumdar, J. Biomol. NMR 2000,
[
[
[
17, 55.
5] K. Pervushin, R. Riek, G. Wider, K. Wüthrich, Proc. Natl. Acad.
Sci. USA 1997, 94, 12366.
6] a) C. Toniolo, M. Crisma, F. Formaggio, C. Peggion, Biopolymers
2001, 60, 396; b) I. L. Karle, P. Balaram, Biochemistry 1990, 29,
6747.
(
a vs. 3 ) in peptides and proteins. However, our results
10
indicate that detection of intramolecular C=O···HꢀN hydro-
3
h
gen bonds in 310 helices by
J
scalar couplings is feasible
[7] a) C. Toniolo, E. Benedetti, Trends Biochem. Sci. 1991, 16, 350;
b) K. A. Bolin, G. L. Millhauser, Acc. Chem. Res. 1999, 32, 1027.
N,C’
only when peptide segments are conformationally rigidified.
[
8] a) M. T. Cung, M. Marraud, J. NØel, Ann. Chim. (Paris) 1972,
83; b) G. M. Bonora, C. Mapelli, C. Toniolo, R. R. Wilkening,
1
Experimental Section
E. S. Stevens, Int. J. Biol. Macromol. 1984, 6, 179; c) B. Pispisa,
A. Palleschi, L. Stella, M. Venanzi, C. Mazzuca, F. Formaggio, C.
Toniolo, Q. B. Broxterman, J. Phys. Chem. B 2002, 106, 5733.
1
5
13
Preparation of unlabeled and NꢀH- or C’=O-labeled, enantiopure
a
[10]
C -methyl-d-valines was performed by DSM Pharma Chemicals.
Terminally protected peptides were synthesized step by step in
solution, beginning from the C-terminus. These sterically demanding
peptide bonds were formed in moderate to good yields either by
the N-ethyl, N’-[(3-(dimethylamino)propyl]carbodiimide/7-aza-1-hy-
[9] N. Juranic, P. K. Ilich, S. Macura, J. Am. Chem. Soc. 1995, 117,
405.
[10] a) W. H. Kruizinga, J. Bolster, R. M. Kellogg, J. Kamphuis,
W. H. J. Boesten, E. M. Meijer, H. E. Schoemaker, J. Org. Chem.
1988, 53, 1826; b) B. Kaptein, W. H. J. Boesten, Q. B. Broxter-
man, P. J. H. Peters, H. E. Schoemaker, J. Kamphuis, Tetrahe-
dron: Asymmetry 1993, 4, 1113.
[11] a) L. A. Carpino, J. Am. Chem. Soc. 1993, 115, 4397; b) L. A.
Carpino, E. S. M. E. Mansour, D. Sadat-Aalaee, J. Org. Chem.
1991, 56, 2611.
[
11a]
[11b]
droxy-1,2,3-benzotriazole
or by the acyl fluoride
C-activation
method. For details of the synthesis and characterization of the five
final peptides and their synthetic intermediates, see Supporting
Information.
IR absorption: The solution IR absorption spectra were recorded
on a Perkin-Elmer model 1720 X FTIR spectrometer. Spectrograde
CDCl (99.8%) was purchased from Aldrich.
[12] Crystal-structure determination of I (C H N O ): crystal
3
36 59 5 8
3
NMR: The H(N)CO type experiments were carried out at 298 K,
dimensions 0.5 0.2 0.2 mm ; orthorhombic, P2 2 2 ; a =
1
1 1
in CD OH on a Bruker Avance 600 instrument. Each spectrum
11.710(3) ,
4064.4(17) ; 1
b = 16.319(4) ,
c = 21.269(5) ;
V=
3
3
ꢀ3
results from 80(t1) 1024(t2) complex data points and was recorded
with 480 scans. The reference spectrum was acquired with the same
parameters in an interleaved way, and the total measuring time for
each pair of spectra was 56 h.
= 1.127 Mgm ; 2qmax = 1208; CuKa radia-
calcd
tion (l = 1.54178 ), q-2q scan mode, T= 293 K; 3750 collected
reflections, 3702 of which were independent; h,k,l limits: ꢀ1 ꢂ
h ꢂ 13, 0 ꢂ k ꢂ 18, 0 ꢂ l ꢂ 23. Intensities were corrected for
Lorentz and polarization effects, not for absorption (m =
X-Ray diffraction: The data were collected on a Philips PW1100
four-circle diffractometer. Single crystals suitable for X-ray diffrac-
tion analysis were grown from ethyl acetate/petroleum ether by vapor
ꢀ1
0.647 cm ). The structure was solved by direct methods by
[
13a]
using the SIR 2002 program,
and anisotropically refined by
[
12]
2
diffusion.
full-matrix block least-squares on F by application of the
[
13b]
SHELXL 97
program. Data/restraints/parameters: 3702/1/
Received: March 9, 2004 [Z54224]
430. Hydrogen atoms were calculated at idealized positions and
2
refined as riding. R = 0.047 [on F ꢃ 4s(F)]; wR = 0.148 (on F ,
1
2
all data). Max./min. residual electron density peaks: + 0.512/
Keywords: helical structures · IR spectroscopy · NMR
.
ꢀ3
ꢀ
0.229 e . CCDC 230-250 contains the supplementary crys-
spectroscopy · peptides · X-ray diffraction
tallographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB21EZ, UK; fax: (+ 44)1223-336-033; or
deposit@ccdc.cam.ac.uk).
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36, 1103; b) G. M. Sheldrick, SHELXL-97 Program for Crystal
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ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3155