Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270110017579/eg3048sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270110017579/eg3048IIsup2.hkl |
CCDC reference: 782540
For related literature, see: Bernstein et al. (1995); Cremer & Pople (1975); Flack (1983); Jagadish et al. (2003, 2008); Murigi et al. (2010); Ntirampebura et al. (2008); Weatherhead-Kloster, Selby, Miller & Mash (2005); Williams et al. (1999).
The synthesis of (R,S)-(I) has previously been reported (Murigi et al., 2010). Neat (R,S)-(I) (105 mg, 0.19 mmol) was heated in a sealed, evacuated tube in an oil bath at 513 K for 20 min, which produced a yellow solid. After cooling to room temperature, the tube was opened, the residue was triturated with CH2Cl2 (3 ml) to dissolve the yellow impurities, and the remaining solid was collected by filtration, giving (R,S)-(II) (45 mg, 0.108 mmol, 58%) as a white solid. The diastereomeric purity of (R,S)-(II) was estimated to be 95% by NMR. Crystallization from hot DMF solution with slow cooling gave, after 2–3 d, a white crystalline mass with a diastereomeric purity >99% as determined by NMR. Characterization data for (R,S)-(II): [α]24D -7.80 (c 0.3, DMSO); m.p. 563 K; IR (KBr, cm-1) 3434, 3034, 2961,1672, 1447, 1276, 1044; 1H NMR (500 MHz, DMSO-d6) δ 2.10 (d, 1H, J = 17.0 Hz), 2.51 (d, 1H, J = 17.0 Hz), 2.90 (m, 2H), 3.14 (dd, 1H, J = 3.5 Hz, J = 13.4 Hz), 3.34 (d, 1H, J = 16.5 Hz), 3.75 (s, 3H), 4.26 (s, 1H), 6.65 (s, 1H), 7.20 (d, 2H, J = 6.6 Hz), 7.27 (s, 1H), 7.32 (m, 3H), 8.22 (s, 1H), 8.48 (s, 1H); 13C NMR (125 MHz, DMSO-d6) δ 38.3, 45.5, 46.3, 55.6, 56.2, 63.8, 108.1, 108.6, 126.7, 127.8, 128.1, 130.3, 133.7, 136.1, 141.1, 154.2, 166.0, 169.9; HRMS (ESI) calcd for C20H18BrN2O3 (M—H)- 413.0506, found 413.0499.
H atoms were all located in a difference map, but those attached to C atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H in the range 0.93–0.98, N—H in the range 0.86–0.89) and Uiso(H) (in the range 1.2–1.5Ueq of the parent atom), after which the positions were refined with riding constraints. The value of the absolute structure parameter is based on 1890 Friedel pairs (Flack, 1983).
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).
C20H19BrN2O3·C3H7NO | F(000) = 1008 |
Mr = 488.38 | Dx = 1.480 Mg m−3 |
Orthorhombic, P212121 | Synchrotron radiation, λ = 0.7749 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 1876 reflections |
a = 6.0741 (7) Å | θ = 3–25° |
b = 13.8336 (16) Å | µ = 1.91 mm−1 |
c = 26.076 (3) Å | T = 100 K |
V = 2191.1 (4) Å3 | Needle, colourless |
Z = 4 | 1.00 × 0.01 × 0.01 mm |
Bruker SMART APEXII CCD diffractometer | 3882 reflections with I > 2σ(I) |
Silicon 111 monochromator | Rint = 0.057 |
0.3 degree ω scans | θmax = 29.0°, θmin = 3.0° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −7→7 |
Tmin = 0.25, Tmax = 0.98 | k = −17→17 |
31454 measured reflections | l = −32→32 |
4493 independent reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.034 | Only H-atom displacement parameters refined |
wR(F2) = 0.073 | Method = Modified Sheldrick
w = 1/[σ2(F2) + ( 0.03P)2 + 2.95P], where P = (max(Fo2,0) + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max = 0.001 |
4479 reflections | Δρmax = 0.60 e Å−3 |
281 parameters | Δρmin = −0.67 e Å−3 |
0 restraints | Absolute structure: Flack (1983), 1890 Friedel-pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.015 (7) |
C20H19BrN2O3·C3H7NO | V = 2191.1 (4) Å3 |
Mr = 488.38 | Z = 4 |
Orthorhombic, P212121 | Synchrotron radiation, λ = 0.7749 Å |
a = 6.0741 (7) Å | µ = 1.91 mm−1 |
b = 13.8336 (16) Å | T = 100 K |
c = 26.076 (3) Å | 1.00 × 0.01 × 0.01 mm |
Bruker SMART APEXII CCD diffractometer | 4493 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3882 reflections with I > 2σ(I) |
Tmin = 0.25, Tmax = 0.98 | Rint = 0.057 |
31454 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | Only H-atom displacement parameters refined |
wR(F2) = 0.073 | Δρmax = 0.60 e Å−3 |
S = 1.00 | Δρmin = −0.67 e Å−3 |
4479 reflections | Absolute structure: Flack (1983), 1890 Friedel-pairs |
281 parameters | Absolute structure parameter: −0.015 (7) |
0 restraints |
Experimental. The needle crystal significantly exceeds the radiation spot size at sample in one dimension. We recognize that this is not an ideal experimental setup. The fragility of the crystals used precluded cutting into a smaller length. However, the crystal was mounted such that the long dimension was orthogonal to the beam, and a multiply redundant data set was measured. We do not believe that this has adversely affected the quality of the data measured. |
x | y | z | Uiso*/Ueq | ||
Br1 | −0.24708 (6) | 0.93502 (2) | 0.732893 (11) | 0.0232 | |
O1 | 0.1620 (4) | 0.60362 (16) | 0.50036 (8) | 0.0216 | |
O2 | 0.8810 (4) | 0.74044 (17) | 0.59505 (9) | 0.0232 | |
O3 | −0.1772 (4) | 0.73383 (16) | 0.76569 (9) | 0.0268 | |
N1 | 0.3119 (4) | 0.68900 (19) | 0.56549 (9) | 0.0169 | |
N2 | 0.7268 (5) | 0.65885 (16) | 0.52939 (8) | 0.0171 | |
C1 | 0.7160 (5) | 0.7066 (2) | 0.57385 (11) | 0.0178 | |
C2 | 0.4920 (5) | 0.7198 (2) | 0.59872 (11) | 0.0161 | |
C3 | 0.3270 (5) | 0.6328 (2) | 0.52393 (11) | 0.0167 | |
C4 | 0.5522 (5) | 0.6048 (2) | 0.50483 (11) | 0.0156 | |
C5 | 0.4530 (5) | 0.8269 (2) | 0.61443 (12) | 0.0187 | |
C6 | 0.2870 (5) | 0.8158 (2) | 0.65724 (10) | 0.0180 | |
C7 | 0.1310 (5) | 0.8810 (2) | 0.67449 (11) | 0.0185 | |
C8 | −0.0191 (6) | 0.8511 (2) | 0.71144 (11) | 0.0207 | |
C9 | −0.0145 (5) | 0.7565 (2) | 0.73092 (12) | 0.0201 | |
C10 | 0.1474 (5) | 0.6925 (2) | 0.71467 (11) | 0.0219 | |
C11 | 0.2958 (5) | 0.7226 (2) | 0.67739 (11) | 0.0178 | |
C12 | 0.4738 (5) | 0.6653 (2) | 0.65075 (11) | 0.0188 | |
C13 | −0.1984 (6) | 0.6345 (3) | 0.77997 (13) | 0.0328 | |
C14 | 0.5921 (5) | 0.4945 (2) | 0.50874 (12) | 0.0203 | |
C15 | 0.6082 (5) | 0.4583 (2) | 0.56369 (13) | 0.0216 | |
C16 | 0.8021 (5) | 0.4697 (2) | 0.59115 (12) | 0.0244 | |
C17 | 0.8163 (5) | 0.4370 (3) | 0.64143 (13) | 0.0287 | |
C18 | 0.6388 (7) | 0.3910 (3) | 0.66458 (14) | 0.0332 | |
C19 | 0.4463 (6) | 0.3785 (3) | 0.63695 (14) | 0.0301 | |
C20 | 0.4300 (6) | 0.4124 (2) | 0.58712 (13) | 0.0238 | |
O4 | 0.9677 (5) | 0.3410 (2) | 0.47242 (11) | 0.0433 | |
N3 | 1.2704 (6) | 0.33877 (19) | 0.42177 (10) | 0.0281 | |
C21 | 1.1428 (6) | 0.3063 (3) | 0.45948 (14) | 0.0300 | |
C22 | 1.4787 (6) | 0.2930 (3) | 0.40944 (15) | 0.0367 | |
C23 | 1.2052 (8) | 0.4224 (3) | 0.39215 (15) | 0.0495 | |
H41 | 0.5544 | 0.6209 | 0.4687 | 0.0171* | |
H51 | 0.5871 | 0.8543 | 0.6273 | 0.0216* | |
H52 | 0.3975 | 0.8662 | 0.5863 | 0.0216* | |
H71 | 0.1254 | 0.9429 | 0.6615 | 0.0221* | |
H101 | 0.1541 | 0.6303 | 0.7289 | 0.0265* | |
H121 | 0.6097 | 0.6728 | 0.6694 | 0.0215* | |
H122 | 0.4336 | 0.5984 | 0.6462 | 0.0227* | |
H131 | −0.3214 | 0.6315 | 0.8033 | 0.0481* | |
H132 | −0.0666 | 0.6129 | 0.7968 | 0.0478* | |
H133 | −0.2260 | 0.5933 | 0.7509 | 0.0477* | |
H141 | 0.7275 | 0.4770 | 0.4918 | 0.0238* | |
H142 | 0.4717 | 0.4633 | 0.4914 | 0.0240* | |
H161 | 0.9235 | 0.4991 | 0.5763 | 0.0280* | |
H171 | 0.9471 | 0.4429 | 0.6593 | 0.0343* | |
H181 | 0.6509 | 0.3704 | 0.6987 | 0.0391* | |
H191 | 0.3265 | 0.3478 | 0.6513 | 0.0361* | |
H201 | 0.3040 | 0.4042 | 0.5679 | 0.0272* | |
H211 | 1.1941 | 0.2506 | 0.4780 | 0.0346* | |
H221 | 1.4743 | 0.2706 | 0.3748 | 0.0537* | |
H223 | 1.5936 | 0.3396 | 0.4129 | 0.0534* | |
H222 | 1.4984 | 0.2400 | 0.4331 | 0.0538* | |
H231 | 1.2000 | 0.4079 | 0.3563 | 0.0731* | |
H233 | 1.3081 | 0.4740 | 0.3981 | 0.0730* | |
H232 | 1.0591 | 0.4426 | 0.4023 | 0.0726* | |
H11 | 0.1833 | 0.7062 | 0.5736 | 0.0197* | |
H21 | 0.8539 | 0.6473 | 0.5185 | 0.0197* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.02134 (14) | 0.02512 (14) | 0.02310 (13) | 0.00248 (19) | 0.00516 (18) | −0.00406 (13) |
O1 | 0.0155 (10) | 0.0251 (12) | 0.0241 (12) | −0.0015 (9) | −0.0001 (9) | −0.0054 (10) |
O2 | 0.0126 (12) | 0.0312 (13) | 0.0259 (12) | −0.0015 (10) | −0.0003 (9) | −0.0069 (10) |
O3 | 0.0269 (12) | 0.0277 (12) | 0.0257 (11) | 0.0018 (9) | 0.0120 (10) | 0.0039 (10) |
N1 | 0.0085 (13) | 0.0243 (13) | 0.0181 (12) | 0.0008 (10) | −0.0003 (9) | −0.0028 (10) |
N2 | 0.0112 (13) | 0.0209 (12) | 0.0191 (11) | −0.0014 (12) | 0.0015 (11) | −0.0030 (9) |
C1 | 0.0160 (19) | 0.0205 (14) | 0.0170 (13) | 0.0005 (13) | −0.0020 (12) | 0.0008 (11) |
C2 | 0.0128 (15) | 0.0217 (16) | 0.0137 (14) | −0.0017 (13) | −0.0018 (12) | −0.0008 (12) |
C3 | 0.0199 (15) | 0.0164 (15) | 0.0139 (14) | −0.0017 (12) | 0.0013 (12) | 0.0011 (12) |
C4 | 0.0104 (15) | 0.0225 (16) | 0.0137 (14) | 0.0006 (12) | 0.0019 (11) | −0.0028 (12) |
C5 | 0.0129 (15) | 0.0215 (17) | 0.0217 (16) | −0.0021 (13) | −0.0007 (12) | −0.0027 (13) |
C6 | 0.017 (2) | 0.0221 (14) | 0.0146 (13) | −0.0020 (13) | −0.0007 (12) | −0.0033 (11) |
C7 | 0.0210 (17) | 0.0191 (16) | 0.0154 (14) | −0.0018 (13) | −0.0007 (12) | −0.0023 (12) |
C8 | 0.0236 (17) | 0.0247 (17) | 0.0137 (14) | 0.0008 (14) | 0.0015 (13) | −0.0042 (12) |
C9 | 0.0205 (15) | 0.0283 (16) | 0.0116 (13) | −0.0031 (13) | 0.0014 (14) | 0.0007 (14) |
C10 | 0.0230 (17) | 0.0216 (16) | 0.0212 (16) | 0.0036 (14) | 0.0016 (13) | 0.0018 (13) |
C11 | 0.0163 (19) | 0.0229 (15) | 0.0142 (13) | −0.0002 (12) | −0.0023 (11) | −0.0019 (11) |
C12 | 0.0146 (15) | 0.0226 (16) | 0.0192 (15) | 0.0044 (13) | 0.0002 (12) | 0.0000 (13) |
C13 | 0.034 (3) | 0.0369 (19) | 0.0270 (18) | 0.0000 (16) | 0.0122 (14) | 0.0094 (14) |
C14 | 0.0181 (16) | 0.0212 (17) | 0.0217 (16) | 0.0027 (13) | −0.0004 (12) | −0.0052 (13) |
C15 | 0.0197 (16) | 0.0178 (17) | 0.0272 (17) | 0.0029 (12) | 0.0026 (13) | −0.0025 (13) |
C16 | 0.0163 (19) | 0.0280 (17) | 0.0289 (17) | 0.0066 (12) | 0.0028 (12) | 0.0007 (13) |
C17 | 0.0213 (17) | 0.0373 (18) | 0.0276 (17) | 0.0072 (16) | −0.0015 (12) | 0.0012 (16) |
C18 | 0.039 (2) | 0.034 (2) | 0.0265 (19) | 0.0134 (18) | 0.0071 (16) | 0.0064 (15) |
C19 | 0.027 (2) | 0.029 (2) | 0.034 (2) | −0.0003 (16) | 0.0119 (15) | 0.0006 (16) |
C20 | 0.0235 (17) | 0.0169 (17) | 0.0310 (18) | 0.0008 (13) | 0.0037 (14) | −0.0041 (13) |
O4 | 0.0365 (17) | 0.0364 (16) | 0.0569 (18) | 0.0035 (13) | 0.0137 (14) | 0.0042 (14) |
N3 | 0.0296 (17) | 0.0286 (14) | 0.0260 (13) | 0.0011 (16) | −0.0018 (15) | 0.0011 (11) |
C21 | 0.030 (2) | 0.0251 (18) | 0.035 (2) | 0.0017 (16) | −0.0007 (16) | −0.0043 (15) |
C22 | 0.033 (2) | 0.039 (2) | 0.038 (2) | 0.0008 (18) | 0.0050 (17) | −0.0043 (18) |
C23 | 0.053 (3) | 0.050 (3) | 0.045 (2) | 0.008 (2) | 0.0070 (19) | 0.0210 (19) |
Br1—C8 | 1.891 (3) | C12—H122 | 0.965 |
O1—C3 | 1.243 (4) | C13—H131 | 0.964 |
O2—C1 | 1.237 (4) | C13—H132 | 0.961 |
O3—C9 | 1.377 (4) | C13—H133 | 0.963 |
O3—C13 | 1.430 (4) | C14—C15 | 1.521 (4) |
N1—C2 | 1.459 (4) | C14—H141 | 0.965 |
N1—C3 | 1.337 (4) | C14—H142 | 0.962 |
N1—H11 | 0.843 | C15—C16 | 1.387 (4) |
N2—C1 | 1.336 (4) | C15—C20 | 1.396 (5) |
N2—C4 | 1.447 (4) | C16—C17 | 1.389 (5) |
N2—H21 | 0.838 | C16—H161 | 0.927 |
C1—C2 | 1.518 (4) | C17—C18 | 1.390 (5) |
C2—C5 | 1.555 (4) | C17—H171 | 0.925 |
C2—C12 | 1.556 (4) | C18—C19 | 1.384 (5) |
C3—C4 | 1.507 (4) | C18—H181 | 0.937 |
C4—C14 | 1.548 (4) | C19—C20 | 1.385 (5) |
C4—H41 | 0.967 | C19—H191 | 0.922 |
C5—C6 | 1.512 (4) | C20—H201 | 0.921 |
C5—H51 | 0.959 | O4—C21 | 1.215 (4) |
C5—H52 | 0.974 | N3—C21 | 1.330 (5) |
C6—C7 | 1.384 (4) | N3—C22 | 1.451 (5) |
C6—C11 | 1.393 (4) | N3—C23 | 1.447 (4) |
C7—C8 | 1.390 (4) | C21—H211 | 0.961 |
C7—H71 | 0.920 | C22—H221 | 0.956 |
C8—C9 | 1.404 (4) | C22—H223 | 0.954 |
C9—C10 | 1.390 (4) | C22—H222 | 0.965 |
C10—C11 | 1.390 (4) | C23—H231 | 0.957 |
C10—H101 | 0.938 | C23—H233 | 0.961 |
C11—C12 | 1.510 (4) | C23—H232 | 0.967 |
C12—H121 | 0.964 | ||
C9—O3—C13 | 117.1 (2) | C2—C12—H122 | 112.0 |
C2—N1—C3 | 126.8 (3) | C11—C12—H122 | 112.3 |
C2—N1—H11 | 117.6 | H121—C12—H122 | 112.5 |
C3—N1—H11 | 115.5 | O3—C13—H131 | 105.9 |
C1—N2—C4 | 127.1 (3) | O3—C13—H132 | 110.0 |
C1—N2—H21 | 115.6 | H131—C13—H132 | 110.1 |
C4—N2—H21 | 115.3 | O3—C13—H133 | 112.2 |
N2—C1—O2 | 122.4 (3) | H131—C13—H133 | 109.7 |
N2—C1—C2 | 118.3 (3) | H132—C13—H133 | 108.8 |
O2—C1—C2 | 119.3 (3) | C4—C14—C15 | 113.3 (3) |
C1—C2—N1 | 112.5 (2) | C4—C14—H141 | 110.4 |
C1—C2—C5 | 111.3 (3) | C15—C14—H141 | 107.2 |
N1—C2—C5 | 108.7 (2) | C4—C14—H142 | 107.0 |
C1—C2—C12 | 112.2 (2) | C15—C14—H142 | 110.1 |
N1—C2—C12 | 108.8 (2) | H141—C14—H142 | 108.7 |
C5—C2—C12 | 102.8 (2) | C14—C15—C16 | 120.2 (3) |
N1—C3—O1 | 122.3 (3) | C14—C15—C20 | 120.8 (3) |
N1—C3—C4 | 118.7 (3) | C16—C15—C20 | 118.9 (3) |
O1—C3—C4 | 119.0 (3) | C15—C16—C17 | 120.2 (3) |
C3—C4—N2 | 112.7 (2) | C15—C16—H161 | 120.6 |
C3—C4—C14 | 112.0 (3) | C17—C16—H161 | 119.2 |
N2—C4—C14 | 111.5 (3) | C16—C17—C18 | 120.7 (3) |
C3—C4—H41 | 105.9 | C16—C17—H171 | 120.1 |
N2—C4—H41 | 107.5 | C18—C17—H171 | 119.2 |
C14—C4—H41 | 106.8 | C17—C18—C19 | 119.1 (3) |
C2—C5—C6 | 101.5 (2) | C17—C18—H181 | 119.4 |
C2—C5—H51 | 109.9 | C19—C18—H181 | 121.5 |
C6—C5—H51 | 110.4 | C18—C19—C20 | 120.5 (3) |
C2—C5—H52 | 112.8 | C18—C19—H191 | 120.8 |
C6—C5—H52 | 112.5 | C20—C19—H191 | 118.8 |
H51—C5—H52 | 109.6 | C15—C20—C19 | 120.6 (3) |
C5—C6—C7 | 129.1 (3) | C15—C20—H201 | 117.6 |
C5—C6—C11 | 110.3 (3) | C19—C20—H201 | 121.8 |
C7—C6—C11 | 120.5 (3) | C21—N3—C22 | 121.6 (3) |
C6—C7—C8 | 118.7 (3) | C21—N3—C23 | 120.4 (3) |
C6—C7—H71 | 120.8 | C22—N3—C23 | 118.0 (3) |
C8—C7—H71 | 120.5 | N3—C21—O4 | 125.6 (4) |
Br1—C8—C7 | 120.2 (2) | N3—C21—H211 | 117.0 |
Br1—C8—C9 | 118.7 (2) | O4—C21—H211 | 117.4 |
C7—C8—C9 | 121.0 (3) | N3—C22—H221 | 109.1 |
C8—C9—O3 | 115.9 (3) | N3—C22—H223 | 108.8 |
C8—C9—C10 | 119.8 (3) | H221—C22—H223 | 109.2 |
O3—C9—C10 | 124.3 (3) | N3—C22—H222 | 107.4 |
C9—C10—C11 | 118.8 (3) | H221—C22—H222 | 111.1 |
C9—C10—H101 | 119.7 | H223—C22—H222 | 111.2 |
C11—C10—H101 | 121.6 | N3—C23—H231 | 111.2 |
C6—C11—C10 | 121.1 (3) | N3—C23—H233 | 109.2 |
C6—C11—C12 | 109.9 (3) | H231—C23—H233 | 109.7 |
C10—C11—C12 | 129.0 (3) | N3—C23—H232 | 109.6 |
C2—C12—C11 | 101.4 (2) | H231—C23—H232 | 107.3 |
C2—C12—H121 | 109.1 | H233—C23—H232 | 109.8 |
C11—C12—H121 | 109.0 | ||
C2—C4—C14—C15 | −3.3 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O2i | 0.84 | 1.98 | 2.820 (5) | 177 |
N2—H21···O1ii | 0.84 | 2.02 | 2.854 (5) | 171 |
C14—H141···O4 | 0.96 | 2.43 | 3.257 (5) | 143 |
C21—H211···O4iii | 0.96 | 2.46 | 3.346 (5) | 154 |
Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z; (iii) x+1/2, −y+1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C20H19BrN2O3·C3H7NO |
Mr | 488.38 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 100 |
a, b, c (Å) | 6.0741 (7), 13.8336 (16), 26.076 (3) |
V (Å3) | 2191.1 (4) |
Z | 4 |
Radiation type | Synchrotron, λ = 0.7749 Å |
µ (mm−1) | 1.91 |
Crystal size (mm) | 1.00 × 0.01 × 0.01 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.25, 0.98 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 31454, 4493, 3882 |
Rint | 0.057 |
(sin θ/λ)max (Å−1) | 0.626 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.073, 1.00 |
No. of reflections | 4479 |
No. of parameters | 281 |
H-atom treatment | Only H-atom displacement parameters refined |
Δρmax, Δρmin (e Å−3) | 0.60, −0.67 |
Absolute structure | Flack (1983), 1890 Friedel-pairs |
Absolute structure parameter | −0.015 (7) |
Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SIR92 (Altomare et al., 1993), CRYSTALS (Betteridge et al., 2003), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O2i | 0.84 | 1.98 | 2.820 (5) | 177 |
N2—H21···O1ii | 0.84 | 2.02 | 2.854 (5) | 171 |
C14—H141···O4 | 0.96 | 2.43 | 3.257 (5) | 143 |
C21—H211···O4iii | 0.96 | 2.46 | 3.346 (5) | 154 |
Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z; (iii) x+1/2, −y+1/2, −z+1. |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
- Information on subscribing
- Sample issue
- Purchase subscription
- Reduced-price subscriptions
- If you have already subscribed, you may need to register
In the course of studies on the properties of piperazinediones (Jagadish et al, 2003; Ntirampebura et al., 2008; Weatherhead-Kloster et al, 2005), we recently prepared the enantiomers of 5-hydroxy-2-aminoindan-2-carboxylic acid, a conformationally constrained tyrosine analog (Murigi et al., 2010). Resolution of this acid was achieved by a process that passed through dipeptides (R,S)-(I) (Scheme) and (S,S)-(I) (not shown). Separation of these diastereomers by silica gel column chromatography was difficult, and so separation was deferred until a later step in the synthesis. However, enough pure (R,S)-(I) was available to carry out a thermolysis to produce the title piperazinedione, (R,S)-(II).
Crystallization of (R,S)-(II) from dimethylformamide (DMF) yielded a mass of very fine, fragile, colorless needle crystals. Single-crystal diffraction analysis was carried out using synchrotron radiation (λ = 0.7749 Å) and yielded reasonable, measurable diffraction to a resolution of approximately 0.8 Å with an exposure time of 7 s per frame. The asymmetric unit of (R,S)-(II) is shown in Fig. 1 and one fully ordered molecule of DMF solvate per molecule of (R,S)-(II) has been incorporated into the structure. The title compound, for which molecular dimensions are generally unexceptional, has a compact, closed conformation, similar to that found in the related compound (R,S)-cyclo[phenylalanyl-(2-amino-4-bromo-7-methoxyindan-2-carboxylic acid)] as reported by Williams et al. (1999). The benzyl group adopts an orientation such that the aryl ring is positioned over the piperazinedione ring, resulting in a torsion angle defined by C2–C4–C14–C15 of -3.3 (3)°. As a consequence of this orientation, atom H122 (bonded to C12) points towards the centroid of the phenyl ring with an H···Cg distance of approximately 2.80 Å. However, the driving force behind this molecular conformation is more likely to be crystal-packing stability rather than the attractive effect of a single C—H···Cg interaction between an aryl ring and an unactivated H atom. The methoxy group is coplanar with the aryl ring to which it is bonded and a mean plane fitted through atoms Br1, O3 and C5 to C13 has an r.m.s. deviation of 0.082 Å. The ring defined by C2, C5, C6, C11 and C12 is present in an envelope conformation with C2 as the `flap atom' and a Cremer–Pople puckering parameter (CPPP) Q = 0.377 (3) Å (Cremer & Pople, 1975). Similarly, the central piperazinedione ring adopts a less puckered boat-like conformation with C2 and C4 as the `bowsprit atoms' and a CPPP of 0.201 (3) Å.
Hydrogen bonding dominates the crystal packing. Reciprocal amide-to-amide hydrogen bonding is commonly (but not exclusively, see e.g. Jagadish et al., 2008) found between adjacent piperazinedione rings in compounds of this type. In this structure adjacent molecules of (R,S)-(II) are connected via an R22(8) motif (Bernstein et al., 1995) composed of two N—H···O interactions to form an infinite tape parallel with the a axis (Fig. 2). Similarly, adjacent DMF molecules are connected via a C(3) motif formed by C21iii—H21iii···O4vi (atoms used as an example in Fig. 2) into a chain which propagates along the a axis. The O atom in DMF acts as a bifurcated acceptor, participating in a further motif which is shown in Fig. 2 by a combination of C14v—H14v···O4iii, C21v—H21v···O4iii and C14vii—H14vii···O4v and is probably most appropriately described as D23(5) since it does not propagate beyond H14v or H14vii. Overall the combination of all hydrogen-bonding interactions results in a one-dimensional ribbon with molecules of (R,S)-(II) forming the outermost parts and DMF forming the innermost part of the ribbon.