Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105001629/bm1602sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270105001629/bm1602Isup2.hkl |
CCDC reference: 268120
The title compound was synthesized by solution-phase peptide synthesis (Gupta et al., 1990). It was crystallized by controlled slow evaporation from a solution of the peptide in a 1:1 me thanol–dioxane mixture at room temperature. Colourless rod-shaped crystals of (I) suitable for X-ray diffraction appeared within 4–5 d.
As the anomalous dispersion effects were not significant, Friedel opposites were merged prior to the final round of refinement. The absolute structure was assigned by reference to the starting materials. Please check added text. All H atoms were generated geometrically and were allowed to ride on their parent atoms, with C—H distances in the range 0.93–0.98 Å and N—H distances of 0.86 Å, and with Uiso(H) = 1.2Ueq(C, N).
Data collection: SMART (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: WinGX (Farrugia, 1999) and PARST (Nardelli, 1995).
C15H18N2O2 | Z = 2 |
Mr = 258.31 | F(000) = 276 |
Triclinic, P1 | Dx = 1.228 Mg m−3 |
a = 6.2384 (5) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 9.8255 (7) Å | Cell parameters from 5071 reflections |
c = 12.5432 (9) Å | θ = 4–54° |
α = 69.344 (1)° | µ = 0.08 mm−1 |
β = 78.054 (1)° | T = 293 K |
γ = 79.396 (1)° | Rod, colourless |
V = 698.64 (9) Å3 | 0.46 × 0.26 × 0.15 mm |
Bruker SMART CCD area-detector diffractometer | 2872 independent reflections |
Radiation source: sealed tube | 2649 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.017 |
ω scans | θmax = 27.3°, θmin = 1.8° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→7 |
Tmin = 0.865, Tmax = 0.988 | k = −12→12 |
7333 measured reflections | l = −15→16 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.045 | H-atom parameters constrained |
wR(F2) = 0.113 | w = 1/[σ2(Fo2) + (0.058P)2 + 0.0935] where P = (Fo2 + 2Fc2)/3 |
S = 1.11 | (Δ/σ)max = 0.013 |
2872 reflections | Δρmax = 0.25 e Å−3 |
348 parameters | Δρmin = −0.17 e Å−3 |
3 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.018 (5) |
C15H18N2O2 | γ = 79.396 (1)° |
Mr = 258.31 | V = 698.64 (9) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.2384 (5) Å | Mo Kα radiation |
b = 9.8255 (7) Å | µ = 0.08 mm−1 |
c = 12.5432 (9) Å | T = 293 K |
α = 69.344 (1)° | 0.46 × 0.26 × 0.15 mm |
β = 78.054 (1)° |
Bruker SMART CCD area-detector diffractometer | 2872 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2649 reflections with I > 2σ(I) |
Tmin = 0.865, Tmax = 0.988 | Rint = 0.017 |
7333 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 3 restraints |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.11 | Δρmax = 0.25 e Å−3 |
2872 reflections | Δρmin = −0.17 e Å−3 |
348 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Weighted least-squares planes through the starred atoms (Nardelli, Musatti, Domiano & Andreetti Ric·Sci.(1965),15(II—A),807). Equation of the plane: m1*X+m2*Y+m3*Z=d Plane 1 m1 = −0.04932(0.00108) m2 = −0.80473(0.00070) m3 = −0.59159(0.00096) D = −12.87551(0.00958) Atom d s d/s (d/s)**2 N1A * 0.0198 0.0025 7.808 60.966 C1A * −0.0671 0.0030 − 22.211 493.322 C1'A * 0.0567 0.0030 18.755 351.747 N2A * −0.0026 0.0025 − 1.014 1.028 C2A * −0.0376 0.0029 − 12.886 166.056 C2'A * 0.0248 0.0029 8.443 71.288 C1A −0.0671 0.0030 − 22.211 493.322 C2A −0.0376 0.0029 − 12.886 166.056 ============ Sum((d/s)**2) for starred atoms 1144.408 Chi-squared at 95% for 3 degrees of freedom: 7.81 The group of atoms deviates significantly from planarity Plane 2 m1 = −0.11106(0.00117) m2 = −0.91424(0.00048) m3 = −0.38967(0.00112) D = −16.94741(0.00774) Atom d s d/s (d/s)**2 N1B * −0.0760 0.0025 − 30.292 917.582 C1B * 0.1339 0.0029 46.126 2127.601 C1'B * −0.0706 0.0031 − 22.862 522.661 N2B * −0.0357 0.0025 − 14.226 202.378 C2B * 0.0900 0.0029 30.982 959.893 C2'B * −0.0112 0.0028 − 3.947 15.579 C1B 0.1339 0.0029 46.126 2127.601 C2B 0.0900 0.0029 30.982 959.893 ============ Sum((d/s)**2) for starred atoms 4745.694 Chi-squared at 95% for 3 degrees of freedom: 7.81 The group of atoms deviates significantly from planarity Dihedral angles formed by LSQ-planes Plane - plane angle (s.u.) angle (s.u.) 1 2 13.66 (0.08) 166.34 (0.08) |
x | y | z | Uiso*/Ueq | ||
N1A | 0.9884 (3) | 0.2550 (3) | 1.0321 (2) | 0.0466 (6) | |
H1A | 1.1142 | 0.2154 | 1.0534 | 0.056* | |
C1A | 0.7985 (4) | 0.1831 (3) | 1.1016 (2) | 0.0428 (6) | |
H1A1 | 0.8302 | 0.0797 | 1.1067 | 0.051* | |
C1'A | 0.5898 (4) | 0.2451 (3) | 1.0481 (2) | 0.0437 (6) | |
O1'A | 0.4266 (3) | 0.1813 (3) | 1.0904 (2) | 0.0641 (7) | |
C1BA | 0.7572 (5) | 0.1887 (4) | 1.2243 (3) | 0.0535 (7) | |
H1B1 | 0.7205 | 0.2904 | 1.2208 | 0.064* | |
H1B2 | 0.6296 | 0.1387 | 1.2664 | 0.064* | |
C1GA | 0.9479 (6) | 0.1215 (4) | 1.2922 (3) | 0.0678 (9) | |
H1GA | 1.0744 | 0.1750 | 1.2506 | 0.081* | |
C1D1 | 0.8873 (9) | 0.1409 (6) | 1.4102 (4) | 0.0969 (15) | |
H1D1 | 0.7778 | 0.0784 | 1.4567 | 0.145* | |
H1D2 | 0.8295 | 0.2412 | 1.4015 | 0.145* | |
H1D3 | 1.0165 | 0.1155 | 1.4469 | 0.145* | |
C2D1 | 1.0160 (9) | −0.0366 (6) | 1.3032 (4) | 0.1013 (16) | |
H2D1 | 0.8887 | −0.0886 | 1.3320 | 0.152* | |
H2D2 | 1.1212 | −0.0780 | 1.3557 | 0.152* | |
H2D3 | 1.0816 | −0.0445 | 1.2290 | 0.152* | |
N2A | 0.5900 (3) | 0.3705 (3) | 0.9574 (2) | 0.0430 (5) | |
H2A | 0.4661 | 0.4088 | 0.9334 | 0.052* | |
C2'A | 0.9912 (4) | 0.3740 (3) | 0.9399 (2) | 0.0409 (6) | |
O2'A | 1.1616 (3) | 0.4289 (2) | 0.88938 (18) | 0.0558 (6) | |
C2A | 0.7745 (4) | 0.4437 (3) | 0.8990 (2) | 0.0398 (6) | |
C2B | 0.5053 (4) | 0.8979 (3) | 0.9907 (2) | 0.0396 (6) | |
C2GA | 0.5936 (5) | 0.6660 (3) | 0.7550 (3) | 0.0477 (7) | |
C1DA | 0.3912 (5) | 0.6960 (3) | 0.8173 (3) | 0.0530 (7) | |
H1DA | 0.3664 | 0.6521 | 0.8969 | 0.064* | |
C2DA | 0.6273 (5) | 0.7377 (4) | 0.6367 (3) | 0.0614 (8) | |
H2DA | 0.7644 | 0.7223 | 0.5936 | 0.074* | |
C1EA | 0.2247 (6) | 0.7917 (4) | 0.7614 (4) | 0.0652 (9) | |
H1EA | 0.0890 | 0.8115 | 0.8039 | 0.078* | |
C2EA | 0.4597 (7) | 0.8317 (4) | 0.5822 (3) | 0.0737 (11) | |
H2EA | 0.4840 | 0.8780 | 0.5028 | 0.088* | |
C2ZA | 0.2590 (6) | 0.8566 (4) | 0.6445 (4) | 0.0719 (11) | |
H2ZA | 0.1452 | 0.9179 | 0.6073 | 0.086* | |
N1B | 0.3035 (3) | 1.0695 (2) | 0.8440 (2) | 0.0445 (6) | |
H1B | 0.1806 | 1.1183 | 0.8240 | 0.053* | |
C1BB | 0.4838 (4) | 1.2735 (3) | 0.6951 (2) | 0.0437 (6) | |
H1B3 | 0.4810 | 1.3248 | 0.7489 | 0.052* | |
H1B4 | 0.6160 | 1.2932 | 0.6385 | 0.052* | |
C1'B | 0.7071 (4) | 1.0617 (3) | 0.8187 (2) | 0.0441 (6) | |
O1'B | 0.8776 (3) | 1.1129 (3) | 0.7679 (2) | 0.0697 (8) | |
C1B | 0.5010 (4) | 1.1087 (3) | 0.7614 (2) | 0.0394 (6) | |
H1B5 | 0.5169 | 1.0572 | 0.7054 | 0.047* | |
C1GB | 0.2835 (5) | 1.3372 (3) | 0.6332 (3) | 0.0504 (7) | |
H1GB | 0.1510 | 1.3187 | 0.6913 | 0.060* | |
C1D2 | 0.2824 (6) | 1.5022 (4) | 0.5794 (4) | 0.0704 (10) | |
H1D4 | 0.4123 | 1.5235 | 0.5231 | 0.106* | |
H1D5 | 0.2805 | 1.5437 | 0.6384 | 0.106* | |
H1D6 | 0.1536 | 1.5435 | 0.5429 | 0.106* | |
C2D2 | 0.2716 (9) | 1.2710 (5) | 0.5450 (4) | 0.0888 (13) | |
H2D4 | 0.4029 | 1.2837 | 0.4887 | 0.133* | |
H2D5 | 0.1450 | 1.3182 | 0.5078 | 0.133* | |
H2D6 | 0.2592 | 1.1683 | 0.5816 | 0.133* | |
N2B | 0.6958 (3) | 0.9595 (3) | 0.9243 (2) | 0.0440 (5) | |
H2B | 0.8159 | 0.9294 | 0.9536 | 0.053* | |
C2BA | 0.7767 (4) | 0.5675 (3) | 0.8094 (2) | 0.0481 (7) | |
H2BA | 0.9161 | 0.5959 | 0.7762 | 0.058* | |
C2'B | 0.2917 (4) | 0.9662 (3) | 0.9473 (2) | 0.0402 (6) | |
O2'B | 0.1152 (3) | 0.9275 (2) | 1.00565 (18) | 0.0510 (5) | |
C2BB | 0.5022 (4) | 0.7878 (3) | 1.0902 (2) | 0.0461 (7) | |
H2BB | 0.3633 | 0.7635 | 1.1291 | 0.055* | |
C2GB | 0.6909 (4) | 0.6995 (3) | 1.1463 (2) | 0.0462 (6) | |
C1DB | 0.8765 (5) | 0.6407 (3) | 1.0870 (3) | 0.0534 (7) | |
H1DB | 0.8857 | 0.6591 | 1.0083 | 0.064* | |
C2DB | 0.6814 (6) | 0.6686 (5) | 1.2634 (3) | 0.0746 (11) | |
H2DB | 0.5575 | 0.7047 | 1.3056 | 0.090* | |
C1EB | 1.0476 (6) | 0.5552 (4) | 1.1434 (3) | 0.0639 (9) | |
H1EB | 1.1699 | 0.5157 | 1.1025 | 0.077* | |
C2EB | 0.8562 (8) | 0.5838 (6) | 1.3185 (3) | 0.0928 (14) | |
H2EB | 0.8493 | 0.5647 | 1.3971 | 0.111* | |
C2ZB | 1.0385 (6) | 0.5283 (5) | 1.2580 (4) | 0.0744 (11) | |
H2ZB | 1.1556 | 0.4724 | 1.2952 | 0.089* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1A | 0.0218 (10) | 0.0564 (14) | 0.0521 (14) | −0.0020 (9) | −0.0152 (9) | −0.0022 (11) |
C1A | 0.0261 (12) | 0.0472 (15) | 0.0506 (16) | −0.0045 (10) | −0.0137 (11) | −0.0059 (12) |
C1'A | 0.0260 (12) | 0.0523 (15) | 0.0496 (15) | −0.0030 (11) | −0.0139 (11) | −0.0090 (13) |
O1'A | 0.0297 (10) | 0.0692 (14) | 0.0762 (15) | −0.0148 (9) | −0.0205 (10) | 0.0086 (12) |
C1BA | 0.0420 (14) | 0.0640 (19) | 0.0490 (16) | −0.0100 (13) | −0.0108 (12) | −0.0077 (14) |
C1GA | 0.0538 (18) | 0.087 (3) | 0.0528 (18) | −0.0186 (17) | −0.0213 (14) | 0.0015 (17) |
C1D1 | 0.124 (4) | 0.109 (4) | 0.058 (2) | −0.035 (3) | −0.035 (2) | −0.005 (2) |
C2D1 | 0.101 (3) | 0.105 (4) | 0.082 (3) | 0.027 (3) | −0.045 (3) | −0.013 (3) |
N2A | 0.0238 (10) | 0.0532 (14) | 0.0470 (12) | −0.0014 (9) | −0.0152 (9) | −0.0065 (11) |
C2'A | 0.0241 (12) | 0.0552 (16) | 0.0416 (14) | −0.0063 (11) | −0.0089 (10) | −0.0108 (12) |
O2'A | 0.0281 (9) | 0.0723 (14) | 0.0551 (12) | −0.0114 (9) | −0.0143 (8) | 0.0008 (11) |
C2A | 0.0287 (12) | 0.0499 (16) | 0.0399 (14) | −0.0040 (11) | −0.0122 (10) | −0.0099 (12) |
C2B | 0.0293 (12) | 0.0453 (14) | 0.0425 (14) | −0.0052 (10) | −0.0099 (10) | −0.0095 (12) |
C2GA | 0.0422 (15) | 0.0432 (14) | 0.0567 (17) | −0.0062 (12) | −0.0220 (13) | −0.0063 (13) |
C1DA | 0.0475 (16) | 0.0486 (16) | 0.0593 (18) | −0.0034 (13) | −0.0148 (13) | −0.0110 (14) |
C2DA | 0.0551 (18) | 0.0587 (19) | 0.0565 (18) | −0.0098 (15) | −0.0140 (15) | 0.0026 (15) |
C1EA | 0.0481 (17) | 0.0477 (17) | 0.095 (3) | 0.0054 (14) | −0.0245 (17) | −0.0153 (18) |
C2EA | 0.087 (3) | 0.060 (2) | 0.063 (2) | −0.0091 (19) | −0.038 (2) | 0.0082 (17) |
C2ZA | 0.064 (2) | 0.0466 (17) | 0.100 (3) | 0.0004 (15) | −0.046 (2) | −0.0034 (18) |
N1B | 0.0243 (10) | 0.0475 (13) | 0.0511 (13) | −0.0030 (9) | −0.0142 (9) | 0.0008 (11) |
C1BB | 0.0362 (13) | 0.0454 (14) | 0.0446 (14) | −0.0097 (11) | −0.0114 (10) | −0.0035 (11) |
C1'B | 0.0251 (12) | 0.0490 (15) | 0.0479 (15) | −0.0054 (11) | −0.0086 (11) | −0.0011 (12) |
O1'B | 0.0294 (10) | 0.0852 (17) | 0.0657 (13) | −0.0138 (10) | −0.0170 (9) | 0.0190 (12) |
C1B | 0.0288 (12) | 0.0431 (14) | 0.0418 (14) | −0.0040 (10) | −0.0110 (10) | −0.0054 (11) |
C1GB | 0.0400 (14) | 0.0487 (16) | 0.0513 (16) | −0.0072 (12) | −0.0172 (12) | 0.0037 (13) |
C1D2 | 0.072 (2) | 0.0491 (18) | 0.076 (2) | −0.0004 (16) | −0.0243 (18) | 0.0001 (16) |
C2D2 | 0.122 (4) | 0.065 (2) | 0.092 (3) | 0.003 (2) | −0.066 (3) | −0.019 (2) |
N2B | 0.0274 (10) | 0.0497 (13) | 0.0465 (12) | −0.0047 (9) | −0.0153 (9) | 0.0001 (10) |
C2BA | 0.0319 (13) | 0.0582 (17) | 0.0495 (16) | −0.0097 (12) | −0.0128 (12) | −0.0064 (14) |
C2'B | 0.0289 (13) | 0.0416 (14) | 0.0473 (15) | −0.0049 (11) | −0.0123 (11) | −0.0073 (12) |
O2'B | 0.0286 (9) | 0.0593 (12) | 0.0533 (12) | −0.0097 (8) | −0.0095 (8) | −0.0001 (10) |
C2BB | 0.0342 (13) | 0.0507 (16) | 0.0475 (16) | −0.0079 (12) | −0.0112 (11) | −0.0050 (13) |
C2GB | 0.0419 (14) | 0.0450 (15) | 0.0437 (15) | −0.0107 (12) | −0.0141 (11) | 0.0022 (12) |
C1DB | 0.0546 (17) | 0.0501 (17) | 0.0481 (16) | −0.0029 (13) | −0.0163 (13) | −0.0041 (13) |
C2DB | 0.066 (2) | 0.092 (3) | 0.0473 (18) | 0.0070 (19) | −0.0149 (16) | −0.0052 (18) |
C1EB | 0.0498 (17) | 0.0542 (18) | 0.071 (2) | 0.0005 (14) | −0.0165 (16) | 0.0005 (16) |
C2EB | 0.099 (3) | 0.114 (4) | 0.049 (2) | 0.009 (3) | −0.038 (2) | −0.003 (2) |
C2ZB | 0.062 (2) | 0.073 (2) | 0.072 (2) | 0.0017 (18) | −0.0350 (18) | 0.0061 (18) |
N1A—C1A | 1.452 (3) | C2EA—H2EA | 0.9300 |
N1A—C2'A | 1.323 (3) | C2ZA—H2ZA | 0.9300 |
N1A—H1A | 0.8600 | N1B—C1B | 1.451 (3) |
C1A—C1'A | 1.516 (3) | N1B—C2'B | 1.333 (3) |
C1A—C1BA | 1.526 (4) | N1B—H1B | 0.8600 |
C1A—H1A1 | 0.9800 | C1BB—C1GB | 1.526 (3) |
C1'A—O1'A | 1.220 (3) | C1BB—C1B | 1.532 (4) |
C1'A—N2A | 1.350 (4) | C1BB—H1B3 | 0.9700 |
C1BA—C1GA | 1.519 (4) | C1BB—H1B4 | 0.9700 |
C1BA—H1B1 | 0.9700 | C1'B—O1'B | 1.217 (3) |
C1BA—H1B2 | 0.9700 | C1'B—N2B | 1.348 (4) |
C1GA—C2D1 | 1.497 (7) | C1'B—C1B | 1.521 (3) |
C1GA—C1D1 | 1.521 (6) | C1B—H1B5 | 0.9800 |
C1GA—H1GA | 0.9800 | C1GB—C2D2 | 1.487 (5) |
C1D1—H1D1 | 0.9600 | C1GB—C1D2 | 1.519 (5) |
C1D1—H1D2 | 0.9600 | C1GB—H1GB | 0.9800 |
C1D1—H1D3 | 0.9600 | C1D2—H1D4 | 0.9600 |
C2D1—H2D1 | 0.9600 | C1D2—H1D5 | 0.9600 |
C2D1—H2D2 | 0.9600 | C1D2—H1D6 | 0.9600 |
C2D1—H2D3 | 0.9600 | C2D2—H2D4 | 0.9600 |
N2A—C2A | 1.400 (3) | C2D2—H2D5 | 0.9600 |
N2A—H2A | 0.8600 | C2D2—H2D6 | 0.9600 |
C2'A—O2'A | 1.230 (3) | N2B—H2B | 0.8600 |
C2'A—C2A | 1.503 (3) | C2BA—H2BA | 0.9300 |
C2A—C2BA | 1.333 (4) | C2'B—O2'B | 1.231 (3) |
C2B—C2BB | 1.332 (4) | C2BB—C2GB | 1.474 (4) |
C2B—N2B | 1.404 (3) | C2BB—H2BB | 0.9300 |
C2B—C2'B | 1.495 (3) | C2GB—C2DB | 1.382 (5) |
C2GA—C1DA | 1.381 (4) | C2GB—C1DB | 1.388 (4) |
C2GA—C2DA | 1.390 (4) | C1DB—C1EB | 1.382 (4) |
C2GA—C2BA | 1.469 (4) | C1DB—H1DB | 0.9300 |
C1DA—C1EA | 1.390 (4) | C2DB—C2EB | 1.390 (5) |
C1DA—H1DA | 0.9300 | C2DB—H2DB | 0.9300 |
C2DA—C2EA | 1.381 (5) | C1EB—C2ZB | 1.357 (6) |
C2DA—H2DA | 0.9300 | C1EB—H1EB | 0.9300 |
C1EA—C2ZA | 1.365 (6) | C2EB—C2ZB | 1.369 (6) |
C1EA—H1EA | 0.9300 | C2EB—H2EB | 0.9300 |
C2EA—C2ZA | 1.362 (6) | C2ZB—H2ZB | 0.9300 |
C2'A—N1A—C1A | 127.8 (2) | C2'B—N1B—C1B | 127.1 (2) |
C2'A—N1A—H1A | 116.1 | C2'B—N1B—H1B | 116.5 |
C1A—N1A—H1A | 116.1 | C1B—N1B—H1B | 116.5 |
N1A—C1A—C1'A | 112.7 (2) | C1GB—C1BB—C1B | 115.7 (2) |
N1A—C1A—C1BA | 112.2 (2) | C1GB—C1BB—H1B3 | 108.4 |
C1'A—C1A—C1BA | 109.4 (2) | C1B—C1BB—H1B3 | 108.4 |
N1A—C1A—H1A1 | 107.4 | C1GB—C1BB—H1B4 | 108.4 |
C1'A—C1A—H1A1 | 107.4 | C1B—C1BB—H1B4 | 108.4 |
C1BA—C1A—H1A1 | 107.4 | H1B3—C1BB—H1B4 | 107.4 |
O1'A—C1'A—N2A | 122.6 (2) | O1'B—C1'B—N2B | 121.8 (2) |
O1'A—C1'A—C1A | 118.6 (2) | O1'B—C1'B—C1B | 120.0 (2) |
N2A—C1'A—C1A | 118.9 (2) | N2B—C1'B—C1B | 118.1 (2) |
C1GA—C1BA—C1A | 115.6 (3) | N1B—C1B—C1'B | 111.9 (2) |
C1GA—C1BA—H1B1 | 108.4 | N1B—C1B—C1BB | 111.6 (2) |
C1A—C1BA—H1B1 | 108.4 | C1'B—C1B—C1BB | 109.6 (2) |
C1GA—C1BA—H1B2 | 108.4 | N1B—C1B—H1B5 | 107.9 |
C1A—C1BA—H1B2 | 108.4 | C1'B—C1B—H1B5 | 107.9 |
H1B1—C1BA—H1B2 | 107.4 | C1BB—C1B—H1B5 | 107.9 |
C2D1—C1GA—C1BA | 112.4 (3) | C2D2—C1GB—C1D2 | 110.6 (3) |
C2D1—C1GA—C1D1 | 110.9 (3) | C2D2—C1GB—C1BB | 113.9 (3) |
C1BA—C1GA—C1D1 | 109.8 (3) | C1D2—C1GB—C1BB | 109.0 (2) |
C2D1—C1GA—H1GA | 107.9 | C2D2—C1GB—H1GB | 107.7 |
C1BA—C1GA—H1GA | 107.9 | C1D2—C1GB—H1GB | 107.7 |
C1D1—C1GA—H1GA | 107.9 | C1BB—C1GB—H1GB | 107.7 |
C1GA—C1D1—H1D1 | 109.5 | C1GB—C1D2—H1D4 | 109.5 |
C1GA—C1D1—H1D2 | 109.5 | C1GB—C1D2—H1D5 | 109.5 |
H1D1—C1D1—H1D2 | 109.5 | H1D4—C1D2—H1D5 | 109.5 |
C1GA—C1D1—H1D3 | 109.5 | C1GB—C1D2—H1D6 | 109.5 |
H1D1—C1D1—H1D3 | 109.5 | H1D4—C1D2—H1D6 | 109.5 |
H1D2—C1D1—H1D3 | 109.5 | H1D5—C1D2—H1D6 | 109.5 |
C1GA—C2D1—H2D1 | 109.5 | C1GB—C2D2—H2D4 | 109.5 |
C1GA—C2D1—H2D2 | 109.5 | C1GB—C2D2—H2D5 | 109.5 |
H2D1—C2D1—H2D2 | 109.5 | H2D4—C2D2—H2D5 | 109.5 |
C1GA—C2D1—H2D3 | 109.5 | C1GB—C2D2—H2D6 | 109.5 |
H2D1—C2D1—H2D3 | 109.5 | H2D4—C2D2—H2D6 | 109.5 |
H2D2—C2D1—H2D3 | 109.5 | H2D5—C2D2—H2D6 | 109.5 |
C1'A—N2A—C2A | 125.7 (2) | C1'B—N2B—C2B | 125.7 (2) |
C1'A—N2A—H2A | 117.2 | C1'B—N2B—H2B | 117.1 |
C2A—N2A—H2A | 117.2 | C2B—N2B—H2B | 117.1 |
O2'A—C2'A—N1A | 122.5 (2) | C2A—C2BA—C2GA | 130.1 (3) |
O2'A—C2'A—C2A | 120.2 (2) | C2A—C2BA—H2BA | 114.9 |
N1A—C2'A—C2A | 117.3 (2) | C2GA—C2BA—H2BA | 114.9 |
C2BA—C2A—N2A | 126.2 (2) | O2'B—C2'B—N1B | 122.6 (2) |
C2BA—C2A—C2'A | 117.0 (2) | O2'B—C2'B—C2B | 120.7 (2) |
N2A—C2A—C2'A | 116.7 (2) | N1B—C2'B—C2B | 116.7 (2) |
C2BB—C2B—N2B | 124.5 (2) | C2B—C2BB—C2GB | 128.2 (3) |
C2BB—C2B—C2'B | 118.6 (2) | C2B—C2BB—H2BB | 115.9 |
N2B—C2B—C2'B | 116.8 (2) | C2GB—C2BB—H2BB | 115.9 |
C1DA—C2GA—C2DA | 118.2 (3) | C2DB—C2GB—C1DB | 118.1 (3) |
C1DA—C2GA—C2BA | 122.8 (3) | C2DB—C2GB—C2BB | 119.3 (3) |
C2DA—C2GA—C2BA | 119.0 (3) | C1DB—C2GB—C2BB | 122.6 (3) |
C2GA—C1DA—C1EA | 120.3 (3) | C1EB—C1DB—C2GB | 120.9 (3) |
C2GA—C1DA—H1DA | 119.9 | C1EB—C1DB—H1DB | 119.6 |
C1EA—C1DA—H1DA | 119.9 | C2GB—C1DB—H1DB | 119.6 |
C2EA—C2DA—C2GA | 120.8 (3) | C2GB—C2DB—C2EB | 120.3 (4) |
C2EA—C2DA—H2DA | 119.6 | C2GB—C2DB—H2DB | 119.9 |
C2GA—C2DA—H2DA | 119.6 | C2EB—C2DB—H2DB | 119.9 |
C2ZA—C1EA—C1DA | 120.4 (4) | C2ZB—C1EB—C1DB | 120.5 (4) |
C2ZA—C1EA—H1EA | 119.8 | C2ZB—C1EB—H1EB | 119.7 |
C1DA—C1EA—H1EA | 119.8 | C1DB—C1EB—H1EB | 119.7 |
C2ZA—C2EA—C2DA | 120.1 (3) | C2ZB—C2EB—C2DB | 120.6 (4) |
C2ZA—C2EA—H2EA | 119.9 | C2ZB—C2EB—H2EB | 119.7 |
C2DA—C2EA—H2EA | 119.9 | C2DB—C2EB—H2EB | 119.7 |
C2EA—C2ZA—C1EA | 120.0 (3) | C1EB—C2ZB—C2EB | 119.7 (3) |
C2EA—C2ZA—H2ZA | 120.0 | C1EB—C2ZB—H2ZB | 120.2 |
C1EA—C2ZA—H2ZA | 120.0 | C2EB—C2ZB—H2ZB | 120.2 |
C2'A—N1A—C1A—C1'A | 8.9 (4) | O1'B—C1'B—C1B—C1BB | −39.7 (4) |
C2'A—N1A—C1A—C1BA | −115.1 (3) | N2B—C1'B—C1B—C1BB | 142.4 (3) |
N1A—C1A—C1'A—O1'A | 170.5 (3) | C1GB—C1BB—C1B—N1B | −55.2 (3) |
C1BA—C1A—C1'A—O1'A | −63.9 (4) | C1GB—C1BB—C1B—C1'B | −179.7 (2) |
N1A—C1A—C1'A—N2A | −11.2 (4) | C1B—C1BB—C1GB—C2D2 | −60.0 (4) |
C1BA—C1A—C1'A—N2A | 114.4 (3) | C1B—C1BB—C1GB—C1D2 | 176.0 (3) |
N1A—C1A—C1BA—C1GA | −57.8 (4) | O1'B—C1'B—N2B—C2B | 177.9 (3) |
C1'A—C1A—C1BA—C1GA | 176.4 (3) | C1B—C1'B—N2B—C2B | −4.3 (4) |
C1A—C1BA—C1GA—C2D1 | −58.6 (4) | C2BB—C2B—N2B—C1'B | 173.6 (3) |
C1A—C1BA—C1GA—C1D1 | 177.5 (3) | C2'B—C2B—N2B—C1'B | −8.8 (4) |
O1'A—C1'A—N2A—C2A | −174.9 (3) | N2A—C2A—C2BA—C2GA | 6.1 (5) |
C1A—C1'A—N2A—C2A | 6.8 (4) | C2'A—C2A—C2BA—C2GA | −175.2 (3) |
C1A—N1A—C2'A—O2'A | 177.5 (3) | C1DA—C2GA—C2BA—C2A | 37.0 (5) |
C1A—N1A—C2'A—C2A | −1.4 (4) | C2DA—C2GA—C2BA—C2A | −146.1 (4) |
C1'A—N2A—C2A—C2BA | −180.0 (3) | C1B—N1B—C2'B—O2'B | −170.4 (3) |
C1'A—N2A—C2A—C2'A | 1.3 (4) | C1B—N1B—C2'B—C2B | 9.7 (4) |
O2'A—C2'A—C2A—C2BA | −2.0 (4) | C2BB—C2B—C2'B—O2'B | 4.3 (4) |
N1A—C2'A—C2A—C2BA | 176.9 (3) | N2B—C2B—C2'B—O2'B | −173.3 (3) |
O2'A—C2'A—C2A—N2A | 176.8 (3) | C2BB—C2B—C2'B—N1B | −175.8 (3) |
N1A—C2'A—C2A—N2A | −4.3 (4) | N2B—C2B—C2'B—N1B | 6.6 (3) |
C2DA—C2GA—C1DA—C1EA | 2.3 (5) | N2B—C2B—C2BB—C2GB | −5.9 (5) |
C2BA—C2GA—C1DA—C1EA | 179.2 (3) | C2'B—C2B—C2BB—C2GB | 176.6 (3) |
C1DA—C2GA—C2DA—C2EA | −2.8 (5) | C2B—C2BB—C2GB—C2DB | 135.7 (4) |
C2BA—C2GA—C2DA—C2EA | −179.8 (3) | C2B—C2BB—C2GB—C1DB | −46.8 (5) |
C2GA—C1DA—C1EA—C2ZA | 0.1 (5) | C2DB—C2GB—C1DB—C1EB | −0.7 (5) |
C2GA—C2DA—C2EA—C2ZA | 0.8 (6) | C2BB—C2GB—C1DB—C1EB | −178.2 (3) |
C2DA—C2EA—C2ZA—C1EA | 1.7 (6) | C1DB—C2GB—C2DB—C2EB | 1.5 (6) |
C1DA—C1EA—C2ZA—C2EA | −2.2 (6) | C2BB—C2GB—C2DB—C2EB | 179.1 (4) |
C2'B—N1B—C1B—C1'B | −21.8 (4) | C2GB—C1DB—C1EB—C2ZB | −0.7 (5) |
C2'B—N1B—C1B—C1BB | −145.0 (3) | C2GB—C2DB—C2EB—C2ZB | −0.8 (7) |
O1'B—C1'B—C1B—N1B | −164.0 (3) | C1DB—C1EB—C2ZB—C2EB | 1.4 (6) |
N2B—C1'B—C1B—N1B | 18.1 (4) | C2DB—C2EB—C2ZB—C1EB | −0.6 (7) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1A—H1A···O1′Ai | 0.86 | 2.04 | 2.874 (3) | 164 |
N2A—H2A···O2′Aii | 0.86 | 2.04 | 2.870 (3) | 161 |
N1B—H1B···O1′Bii | 0.86 | 2.17 | 2.915 (3) | 146 |
N2B—H2B···O2′Bi | 0.86 | 2.10 | 2.926 (3) | 162 |
C1A—H1A1···O2′Biii | 0.98 | 2.54 | 3.314 (4) | 136 |
C1GA—H1GA···O1′Ai | 0.98 | 2.65 | 3.484 (4) | 144 |
C1GB—H1GB···O1′Bii | 0.98 | 2.67 | 3.432 (4) | 135 |
C1BB—H1B3···O2′Aiv | 0.97 | 2.68 | 3.432 (4) | 135 |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) x+1, y−1, z; (iv) x−1, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | C15H18N2O2 |
Mr | 258.31 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.2384 (5), 9.8255 (7), 12.5432 (9) |
α, β, γ (°) | 69.344 (1), 78.054 (1), 79.396 (1) |
V (Å3) | 698.64 (9) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.46 × 0.26 × 0.15 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.865, 0.988 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7333, 2872, 2649 |
Rint | 0.017 |
(sin θ/λ)max (Å−1) | 0.646 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.113, 1.11 |
No. of reflections | 2872 |
No. of parameters | 348 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.25, −0.17 |
Computer programs: SMART (Bruker, 1998), SAINT-Plus (Bruker, 2001), SAINT-Plus, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPIII (Farrugia, 1997) and PLATON (Spek, 2003), WinGX (Farrugia, 1999) and PARST (Nardelli, 1995).
C2'A—N1A—C1A—C1'A | 8.9 (4) | C2'B—N1B—C1B—C1'B | −21.8 (4) |
N1A—C1A—C1'A—N2A | −11.2 (4) | N2B—C1'B—C1B—N1B | 18.1 (4) |
C1A—C1'A—N2A—C2A | 6.8 (4) | C1B—C1'B—N2B—C2B | −4.3 (4) |
C1A—N1A—C2'A—C2A | −1.4 (4) | C2'B—C2B—N2B—C1'B | −8.8 (4) |
C1'A—N2A—C2A—C2'A | 1.3 (4) | C1B—N1B—C2'B—C2B | 9.7 (4) |
N1A—C2'A—C2A—N2A | −4.3 (4) | N2B—C2B—C2'B—N1B | 6.6 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1A—H1A···O1'Ai | 0.86 | 2.04 | 2.874 (3) | 164 |
N2A—H2A···O2'Aii | 0.86 | 2.04 | 2.870 (3) | 161 |
N1B—H1B···O1'Bii | 0.86 | 2.17 | 2.915 (3) | 146 |
N2B—H2B···O2'Bi | 0.86 | 2.10 | 2.926 (3) | 162 |
C1A—H1A1···O2'Biii | 0.98 | 2.54 | 3.314 (4) | 136 |
C1GA—H1GA···O1'Ai | 0.98 | 2.65 | 3.484 (4) | 144 |
C1GB—H1GB···O1'Bii | 0.98 | 2.67 | 3.432 (4) | 135 |
C1BB—H1B3···O2'Aiv | 0.97 | 2.68 | 3.432 (4) | 135 |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) x+1, y−1, z; (iv) x−1, y+1, z. |
Diketopiperazines (2,5-piperazinediones) are the simplest models for the study of cis-peptide geometries and for studying the influence of side chains on ring conformations. The present structure analysis of the title molecule, cyclo-(L-Leu-ΔPhe) (LΔF), (I), was undertaken as a continuation of our investigations of the diketopiperazine (DKP) structure (Suguna et al., 1982, 1984, 1985) and of the peptides containing ΔPhe residues. While the structures of several DKPs containing protein amino acids and α-amino isobutyric acid (AIB) are known, this is perhaps the first report of a DKP incorporating a dehydro amino acid residue. In our laboratory, this constrained amino acid has been successfully incorporated in the de novo design of secondary structure elements, 310 helices and supersecondary structural elements: the helical assemblies (Rajashankar et al., 1996; Ramagopal et al., 2001; Rudresh et al., 2004; Mathur et al., 2004). The α,β-dehydrophenyalanine residues induce β bend structures in short peptides and a 310 helical conformation in longer peptides. The most favourable conformations of ΔPhe are (ϕ, ψ) ~ (−60, −30°), (−60, 150°), (80, 0°) or their enantiomers. In the case of linear peptides, (ϕ, ψ) usually assumes the conformation (60, 30°) or (−60, −30°). The leucyl side chain is of particular interest, since many diketopiperazines containing this residue have been found to be the factors causing a bitter taste (Minamiura et al., 1972; Shiba et al., 1974, 1981).
In the structure of (I), two diketopiperazine molecules, A and B, are present in the asymmetric unit. The displacement ellipsoid representation of the molecule shown in Fig. 1 illustrates an overall view of the structure. The two molecules are chemically equivalent but crystallographically independent. They are antiparallel to each other and are arranged such that the ΔPhe side chain of one shields the (DKP) ring of the other. The arrangement is different from that seen in other DKPs, such as cyclo-(L-Leu-L-Tyr) (Suguna et al., 1984), cyclo-(Phe–Phe) (Benedetti et al., 1976) or cyclo-(Pro-D-Phe) (Ramani et al., 1976), where the aromatic ring of one molecule shields the DKP ring of the same molecule. This behaviour may be attributed to the fact that the ΔPhe residue as a whole is rigid and rotation about the Cα═Cβ is restricted. Due to this, the entire molecule takes an extended rather than a folded conformation.
The ϕ and ψ angles of the ΔPhe residue are very different from what is observed in ΔPhe-containing linear peptides, i.e. (60, 30°) and (−60, −30°). They are close to zero, i.e. ϕ (C1'A—N2A—C2A—-C2'A) 1.3 (4)°, ψ (N1—C2'A—C2A—N2A) −4.3 (4)° for molecule A and ϕ (C1'B—N2B—C2B—C2'B) −8.8 (4)°, ψ (N1B—C2'B—C2B—N2B) 6.6 (3)° for molecule B. These values for ΔPhe may be a consequence of the cyclization of the peptide. The angles at the Cβ atoms of the leucyl side chains are 112.2 (2) and 111.6 (2)° in molecules A and B, respectively, indicating that these atoms are axial to the DKP rings. The molecule acquires an extended conformation, with the χ2 dihedral angles being 177.5 (3) and 176.0 (3)°, respectively, for the two independent molecules, A and B.
The torsion angles ϕ, ψ and ω (Table 1) of the peptide backbone indicate that the DKP ring takes a boat conformation, as in the case of other phenylalanine-containing DKPs (Suguna et al., 1985; Ramani et al., 1976; Benedetti et al., 1976). The deviations of the leucyl and ΔPhe Cα atoms from the mean plane passing through the remaining atoms of the DKP ring are −0.067 and −0.04 Å for molecule A, and 0.13 and 0.09 Å for molecule B, respectively. The DKP ring thus assumes a boat conformation in both molecules.
The crystal packing of (I) is illustrated in Fig. 2. Molecules A and B form hydrogen-bonded ribbons with molecules of the same type via by N—H···O interactions between adjacent molecules related by translation along the a axis (Table 2). Weaker C—H···O interactions, observed between the two independent molecules, A and B, link the molecules into an overall three-dimensional network.