Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199015619/bm1380sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270199015619/bm1380Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270199015619/bm1380IIsup3.hkl |
Compound (I) was prepared by the overnight reaction of L-threonine and o-phthalaldehyde in refluxing CH3CN under N2 (Allin et al., 1996). Filtration of the hot solution and subsequent slow cooling of the filtrate allowed the isolation of colourless plates of (I) (m.p. 458–460 K, uncorrected). Spectroscopic analysis: IR (KBr, cm-1): (νOH) 3256, (νC═O) 1748, 1656; 1H NMR (400 MHz, δ, d6 DMSO): 1.07 (d, 3H, CH3), 4.46 (m, 1H, CH), 4.69 (s, 2H, CH2), 4.80 (d, 1H, CH), 5.29 (br s, 1H, O—H), 7.46–7.52, 7.61–7.66, 7.71–7.73 (m, 4H, C6H4). Compound (II) was prepared as detailed for (I) above, using DL-threonine as the starting material, and colourless blocks of (II) were obtained from solution (m.p. 424–427 K, uncorrected). Spectroscopic analysis: IR (KBr, cm-1): (νOH) 3234, (νC═O) 1759, 1644; 1H NMR (400 MHz, δ, d6 DMSO): 1.07 (m, 3H, CH3), 4.45 (m, 1H, CH), 4.68 (s, 2H, CH2), 4.73 (d, 1H, CH), 5.31 (br s, 1H, O—H), 7.48–7.52, 7.60–7.66, 7.71–7.73 (m, 4H, C6H4).
For both compounds, all H atoms bound to C were treated as riding, with the SHELXL97 (Sheldrick, 1997a) defaults for C—H distances and with Uiso(H) = 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for others. For (I), H atoms bound to O were refined with isotropic displacement parameters, while for (II), H atoms bound to O were located from difference Fourier maps in the penultimate stages of refinement and subsequently treated as rigid rotating groups with Uiso(H) = 1.5Ueq(O). (Please check new text.)
For both compounds, data collection: CAD-4-PC Software (Enraf-Nonius, 1992); cell refinement: CAD-4-PC Software; data reduction: NRCVAX96 (Gabe et al., 1989); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997b); program(s) used to refine structure: NRCVAX96 and SHELXL97 (Sheldrick, 1997a); molecular graphics: ORTEPIII (Burnett & Johnson, 1996), ORTEX (McArdle, 1995) and PLATON (Spek, 1998); software used to prepare material for publication: NRCVAX96, SHELXL97 and PREP8 (Ferguson, 1998).
C12H13NO4 | Dx = 1.392 Mg m−3 |
Mr = 235.23 | Melting point: 459 K |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.7107 Å |
a = 6.2209 (6) Å | Cell parameters from 25 reflections |
b = 11.9726 (13) Å | θ = 9.7–19.6° |
c = 15.0705 (12) Å | µ = 0.11 mm−1 |
V = 1122.5 (2) Å3 | T = 294 K |
Z = 4 | Plate, colourless |
F(000) = 496 | 0.32 × 0.14 × 0.12 mm |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.020 |
Radiation source: X-ray tube | θmax = 25.0°, θmin = 2.2° |
Graphite monochromator | h = 0→7 |
ω/2θ scans | k = −14→14 |
3932 measured reflections | l = −17→17 |
1967 independent reflections | 3 standard reflections every 120 min |
1441 reflections with I > 2σ(I) | intensity decay: variation <1% |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.040 | Calculated w = 1/[σ2(Fo2) + (0.0538P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.096 | (Δ/σ)max = 0.001 |
S = 1.01 | Δρmax = 0.16 e Å−3 |
1967 reflections | Δρmin = −0.15 e Å−3 |
163 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997a), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.011 (3) |
Primary atom site location: structure-invariant direct methods | Absolute structure: Flack (1983) |
Secondary atom site location: difference Fourier map | Absolute structure parameter: not reliably determined |
C12H13NO4 | V = 1122.5 (2) Å3 |
Mr = 235.23 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 6.2209 (6) Å | µ = 0.11 mm−1 |
b = 11.9726 (13) Å | T = 294 K |
c = 15.0705 (12) Å | 0.32 × 0.14 × 0.12 mm |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.020 |
3932 measured reflections | 3 standard reflections every 120 min |
1967 independent reflections | intensity decay: variation <1% |
1441 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.040 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.096 | Δρmax = 0.16 e Å−3 |
S = 1.01 | Δρmin = −0.15 e Å−3 |
1967 reflections | Absolute structure: Flack (1983) |
163 parameters | Absolute structure parameter: not reliably determined |
0 restraints |
Geometry. Specific hydrogen bonds & contacts (with e.s.d.'s except fixed and riding H) ============================================================== D—H H···A D···A D—H···A Interaction ============================================================== 0.81 (4) 1.87 (4) 2.659 (3) 162 (4) O1—H1···O4_$2 0.82 (4) 1.90 (4) 2.718 (3) 174 (4) O4—H4···O3_$3 0.97 2.57 3.513 (4) 165.1 C10—H10A···O3_$3 0.93 3.11 3.781 (4) 130.2 C5—H5···C4_$4 0.93 3.07 3.941 (3) 156.0 C5—H5···C5_$4 0.93 3.06 3.913 (4) 153.3 C5—H5···C6_$4 0.93 3.11 3.743 (4) 127.3 C5—H5···C7_$4 0.93 3.19 3.618 (4) 110.2 C5—H5···C8_$4 0.93 3.19 3.638 (4) 111.7 C5—H5···C9_$4 0.98 3.26 3.879 (4) 122.5 C11—H11···C4_$5 0.98 2.98 3.798 (4) 141.7 C11—H11···C5_$5 0.98 2.76 3.726 (4) 167.6 C11—H11···C6_$5 0.98 2.91 3.782 (4) 149.3 C11—H11···C7_$5 0.98 3.22 3.882 (4) 126.3 C11—H11···C8_$5 0.98 3.38 3.920 (4) 116.9 C11—H11···C9_$5 0.96 3.28 4.145 (4) 151.4 C12—H12C···N1_$5 0.96 3.10 3.777 (4) 128.7 C12—H12C···C3_$5 0.96 2.91 3.508 (4) 121.8 C12—H12C···C4_$5 0.96 2.96 3.730 (4) 138.2 C12—H12C···C9_$5 0.96 3.21 4.146 (4) 165.9 C12—H12C···C10_$5 0.93 2.81 3.554 (4) 137.4 C7—H7···O2_$6 The interaction details are also described in the hydrogen bonding table. Mean plane data ex-SHELXL97 for molecule (I) ############################################ Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 6.1626(0.0015)x + 1.6324(0.0187)y + 0.1081(0.0230)z = 3.9677(0.0215) * -0.0031 (0.0008) O1 * -0.0040 (0.0010) O2 * 0.0098 (0.0026) C1 * -0.0027 (0.0007) C2 1.0724 (0.0046) C11 - 0.0149 (0.0047) N1 Rms deviation of fitted atoms = 0.0057 -2.5506(0.0060)x + 9.1968(0.0082)y + 7.4112(0.0141)z = 6.3865(0.0084) Angle to previous plane (with approximate e.s.d.) = 72.67 (10) * -0.0051 (0.0018) C4 * -0.0011 (0.0020) C5 * 0.0068 (0.0020) C6 * -0.0064 (0.0020) C7 * 0.0002 (0.0020) C8 * 0.0055 (0.0018) C9 0.0088 (0.0043) N1 Rms deviation of fitted atoms = 0.0049 -2.5910(0.0079)x + 9.2245(0.0101)y + 7.2729(0.0172)z = 6.2940(0.0127) Angle to previous plane (with approximate e.s.d.) = 0.66 (18) * -0.0179 (0.0017) N1 * 0.0154 (0.0016) C3 * -0.0065 (0.0016) C4 * -0.0035 (0.0016) C9 * 0.0124 (0.0016) C10 0.0713 (0.0040) O3 1.4338 (0.0054) C1 0.0604 (0.0045) C2 Rms deviation of fitted atoms = 0.0124 6.1626(0.0015)x + 1.6324(0.0187)y + 0.1081(0.0230)z = 3.9677(0.0215) Angle to previous plane (with approximate e.s.d.) = 72.30 (11) * -0.0031 (0.0008) O1 * -0.0040 (0.0010) O2 * 0.0098 (0.0026) C1 * -0.0027 (0.0007) C2 1.0724 (0.0046) C11 - 0.0149 (0.0047) N1 Rms deviation of fitted atoms = 0.0057 2.0571(0.0200)x - 8.6012(0.0129)y + 9.2232(0.0343)z = 8.3712(0.0188) Angle to previous plane (with approximate e.s.d.) = 76.47 (2) * 0.0000 (0.0000) O4 * 0.0000 (0.0000) C11 * 0.0000 (0.0000) C12 - 2.4600 (0.0045) N1 - 1.1646 (0.0064) C2 Rms deviation of fitted atoms = 0.0000 |
x | y | z | Uiso*/Ueq | ||
O1 | 0.5667 (4) | 0.22403 (18) | 0.98584 (13) | 0.0491 (6) | |
O2 | 0.5280 (4) | 0.37524 (18) | 0.90086 (15) | 0.0652 (7) | |
O3 | 0.2206 (3) | 0.18768 (18) | 0.71575 (12) | 0.0457 (5) | |
O4 | 0.9620 (3) | 0.1801 (2) | 0.86098 (13) | 0.0462 (5) | |
N1 | 0.5624 (3) | 0.24890 (18) | 0.74759 (14) | 0.0349 (5) | |
C1 | 0.5560 (5) | 0.2772 (3) | 0.90909 (18) | 0.0399 (7) | |
C2 | 0.5774 (4) | 0.1939 (2) | 0.83343 (15) | 0.0339 (6) | |
C3 | 0.3828 (4) | 0.2419 (2) | 0.69714 (16) | 0.0325 (6) | |
C4 | 0.4196 (4) | 0.3118 (2) | 0.61848 (16) | 0.0320 (6) | |
C5 | 0.2828 (5) | 0.3318 (2) | 0.54723 (17) | 0.0394 (7) | |
C6 | 0.3540 (6) | 0.4043 (3) | 0.48278 (19) | 0.0499 (9) | |
C7 | 0.5552 (6) | 0.4542 (2) | 0.48836 (18) | 0.0478 (8) | |
C8 | 0.6884 (5) | 0.4343 (2) | 0.55979 (19) | 0.0425 (8) | |
C9 | 0.6180 (4) | 0.3623 (2) | 0.62557 (17) | 0.0339 (6) | |
C10 | 0.7226 (4) | 0.3259 (2) | 0.71118 (18) | 0.0383 (7) | |
C11 | 0.7722 (4) | 0.1165 (2) | 0.84408 (16) | 0.0355 (7) | |
C12 | 0.7996 (6) | 0.0391 (2) | 0.76572 (18) | 0.0471 (8) | |
H1 | 0.542 (7) | 0.266 (3) | 1.027 (3) | 0.091 (14)* | |
H4 | 1.047 (6) | 0.181 (3) | 0.820 (2) | 0.083 (14)* | |
H2 | 0.4508 | 0.1455 | 0.8375 | 0.041* | |
H5 | 0.1490 | 0.2975 | 0.5433 | 0.047* | |
H6 | 0.2658 | 0.4203 | 0.4346 | 0.060* | |
H7 | 0.6007 | 0.5016 | 0.4433 | 0.057* | |
H8 | 0.8224 | 0.4684 | 0.5637 | 0.051* | |
H10A | 0.8583 | 0.2884 | 0.7003 | 0.046* | |
H10B | 0.7465 | 0.3888 | 0.7505 | 0.046* | |
H11 | 0.7460 | 0.0699 | 0.8964 | 0.043* | |
H12A | 0.9228 | −0.0077 | 0.7751 | 0.071* | |
H12B | 0.8198 | 0.0824 | 0.7127 | 0.071* | |
H12C | 0.6737 | −0.0066 | 0.7595 | 0.071* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0561 (14) | 0.0606 (14) | 0.0306 (11) | 0.0086 (11) | 0.0091 (11) | −0.0019 (10) |
O2 | 0.091 (2) | 0.0475 (13) | 0.0569 (14) | 0.0125 (13) | 0.0100 (13) | 0.0000 (11) |
O3 | 0.0331 (11) | 0.0667 (13) | 0.0372 (10) | −0.0122 (12) | −0.0003 (9) | 0.0037 (10) |
O4 | 0.0330 (11) | 0.0746 (14) | 0.0309 (11) | −0.0032 (12) | −0.0020 (10) | −0.0073 (10) |
N1 | 0.0261 (12) | 0.0471 (13) | 0.0313 (11) | −0.0073 (12) | −0.0022 (10) | 0.0094 (10) |
C1 | 0.0313 (17) | 0.0486 (18) | 0.0400 (16) | 0.0024 (15) | 0.0047 (14) | 0.0020 (13) |
C2 | 0.0321 (16) | 0.0435 (15) | 0.0261 (13) | −0.0043 (14) | 0.0031 (11) | 0.0069 (12) |
C3 | 0.0276 (15) | 0.0430 (16) | 0.0269 (13) | −0.0026 (14) | 0.0042 (11) | −0.0039 (12) |
C4 | 0.0337 (17) | 0.0359 (14) | 0.0265 (13) | 0.0040 (15) | 0.0012 (11) | −0.0025 (11) |
C5 | 0.0367 (16) | 0.0482 (18) | 0.0333 (14) | 0.0002 (15) | 0.0005 (14) | −0.0069 (13) |
C6 | 0.066 (2) | 0.054 (2) | 0.0292 (15) | 0.0130 (17) | −0.0045 (15) | 0.0001 (14) |
C7 | 0.068 (2) | 0.0421 (17) | 0.0333 (15) | 0.0057 (18) | 0.0108 (17) | 0.0065 (13) |
C8 | 0.0454 (19) | 0.0383 (17) | 0.0437 (17) | −0.0049 (14) | 0.0106 (15) | 0.0052 (13) |
C9 | 0.0352 (16) | 0.0333 (14) | 0.0333 (14) | 0.0031 (13) | 0.0031 (13) | −0.0007 (12) |
C10 | 0.0295 (15) | 0.0445 (16) | 0.0409 (14) | −0.0063 (15) | 0.0015 (14) | 0.0074 (13) |
C11 | 0.0361 (17) | 0.0412 (16) | 0.0292 (14) | −0.0022 (14) | 0.0030 (12) | 0.0058 (12) |
C12 | 0.051 (2) | 0.0486 (18) | 0.0422 (17) | 0.0009 (16) | 0.0075 (15) | −0.0005 (14) |
O1—C1 | 1.322 (3) | C3—C4 | 1.469 (4) |
O2—C1 | 1.193 (3) | C4—C5 | 1.391 (4) |
O3—C3 | 1.232 (3) | C4—C9 | 1.379 (4) |
O4—C11 | 1.427 (3) | C5—C6 | 1.376 (4) |
N1—C2 | 1.454 (3) | C6—C7 | 1.389 (4) |
N1—C3 | 1.354 (3) | C7—C8 | 1.379 (4) |
N1—C10 | 1.465 (3) | C8—C9 | 1.384 (4) |
C1—C2 | 1.520 (4) | C9—C10 | 1.509 (4) |
C2—C11 | 1.534 (4) | C11—C12 | 1.511 (3) |
C2—N1—C3 | 121.6 (2) | C3—C4—C9 | 109.1 (2) |
C2—N1—C10 | 125.1 (2) | C5—C4—C9 | 122.2 (2) |
C3—N1—C10 | 113.0 (2) | C4—C5—C6 | 117.2 (3) |
O1—C1—O2 | 124.9 (3) | C5—C6—C7 | 121.2 (3) |
O1—C1—C2 | 109.7 (2) | C6—C7—C8 | 121.0 (3) |
O2—C1—C2 | 125.4 (3) | C7—C8—C9 | 118.5 (3) |
N1—C2—C1 | 111.4 (2) | C4—C9—C8 | 120.0 (3) |
N1—C2—C11 | 114.7 (2) | C4—C9—C10 | 109.0 (2) |
C1—C2—C11 | 112.7 (2) | C8—C9—C10 | 131.0 (3) |
O3—C3—N1 | 125.5 (2) | N1—C10—C9 | 102.0 (2) |
O3—C3—C4 | 127.7 (2) | O4—C11—C2 | 110.5 (2) |
N1—C3—C4 | 106.8 (2) | O4—C11—C12 | 111.9 (2) |
C3—C4—C5 | 128.7 (3) | C2—C11—C12 | 112.2 (2) |
C3—N1—C2—C1 | −104.5 (3) | C4—C5—C6—C7 | 0.8 (4) |
C10—N1—C2—C1 | 68.3 (3) | C5—C6—C7—C8 | −1.4 (4) |
C3—N1—C2—C11 | 125.9 (3) | C6—C7—C8—C9 | 0.7 (4) |
C10—N1—C2—C11 | −61.3 (3) | C5—C4—C9—C8 | −1.0 (4) |
O2—C1—C2—N1 | 0.8 (4) | C3—C4—C9—C8 | −179.0 (2) |
O1—C1—C2—N1 | 178.9 (2) | C5—C4—C9—C10 | 178.4 (2) |
O2—C1—C2—C11 | 131.4 (3) | C3—C4—C9—C10 | 0.4 (3) |
O1—C1—C2—C11 | −50.5 (3) | C7—C8—C9—C4 | 0.4 (4) |
C2—N1—C3—O3 | −2.3 (4) | C7—C8—C9—C10 | −178.7 (3) |
C10—N1—C3—O3 | −175.9 (3) | C3—N1—C10—C9 | −2.9 (3) |
C2—N1—C3—C4 | 176.8 (2) | C2—N1—C10—C9 | −176.3 (2) |
C10—N1—C3—C4 | 3.2 (3) | C4—C9—C10—N1 | 1.4 (3) |
O3—C3—C4—C9 | 176.9 (3) | C8—C9—C10—N1 | −179.3 (3) |
N1—C3—C4—C9 | −2.2 (3) | N1—C2—C11—O4 | 78.1 (3) |
O3—C3—C4—C5 | −0.9 (5) | C1—C2—C11—O4 | −50.8 (3) |
N1—C3—C4—C5 | −180.0 (3) | N1—C2—C11—C12 | −47.5 (3) |
C9—C4—C5—C6 | 0.3 (4) | C1—C2—C11—C12 | −176.4 (2) |
C3—C4—C5—C6 | 177.9 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4i | 0.81 (4) | 1.87 (4) | 2.659 (3) | 162 (4) |
O4—H4···O3ii | 0.82 (4) | 1.90 (4) | 2.718 (3) | 174 (4) |
C10—H10A···O3ii | 0.97 | 2.57 | 3.513 (4) | 165 |
C5—H5···Cg2iii | 0.93 | 2.80 | 3.512 (3) | 134 |
C11—H11···Cg2iv | 0.98 | 2.77 | 3.573 (3) | 140 |
C12—H12C···Cg1iv | 0.96 | 2.84 | 3.672 (3) | 145 |
Symmetry codes: (i) x−1/2, −y+1/2, −z+2; (ii) x+1, y, z; (iii) x−1/2, −y+1/2, −z+1; (iv) −x+1, y−1/2, −z+3/2. |
C12H13NO4 | Dx = 1.348 Mg m−3 |
Mr = 235.23 | Melting point: 426 K |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.7107 Å |
a = 5.9772 (7) Å | Cell parameters from 25 reflections |
b = 14.3906 (12) Å | θ = 9.7–18.3° |
c = 13.4926 (16) Å | µ = 0.10 mm−1 |
β = 93.131 (7)° | T = 294 K |
V = 1158.8 (2) Å3 | Block, colourless |
Z = 4 | 0.39 × 0.35 × 0.21 mm |
F(000) = 496 |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.008 |
Radiation source: X-ray tube | θmax = 25.5°, θmin = 2.1° |
Graphite monochromator | h = −7→7 |
ω/2θ scans | k = 0→17 |
2242 measured reflections | l = 0→16 |
2155 independent reflections | 3 standard reflections every 120 min |
1623 reflections with I > 2σ(I) | intensity decay: variation <0.5% |
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)] = 0.034 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.086 | Calculated w = 1/[σ2(Fo2) + (0.0378P)2 + 0.2183P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max = 0.001 |
2155 reflections | Δρmax = 0.16 e Å−3 |
158 parameters | Δρmin = −0.12 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997a), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.044 (3) |
C12H13NO4 | V = 1158.8 (2) Å3 |
Mr = 235.23 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 5.9772 (7) Å | µ = 0.10 mm−1 |
b = 14.3906 (12) Å | T = 294 K |
c = 13.4926 (16) Å | 0.39 × 0.35 × 0.21 mm |
β = 93.131 (7)° |
Enraf-Nonius CAD-4 diffractometer | Rint = 0.008 |
2242 measured reflections | 3 standard reflections every 120 min |
2155 independent reflections | intensity decay: variation <0.5% |
1623 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.034 | 0 restraints |
wR(F2) = 0.086 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.16 e Å−3 |
2155 reflections | Δρmin = −0.12 e Å−3 |
158 parameters |
Experimental. C—H···pi(arene) hydrogen bonds (with e.s.d.'s except fixed and riding H) ============================================================== D—H H···A D···A D—H···A Interaction ============================================================== 0.98 3.06 3.819 (2) 135.7 C11—H11···C4_$4 0.98 2.98 3.829 (2) 146.2 C11—H11···C5_$4 0.98 2.94 3.895 (2) 165.2 C11—H11···C6_$4 0.98 3.01 3.965 (2) 166.2 C11—H11···C7_$4 0.98 3.11 3.977 (2) 147.6 C11—H11···C8_$4 0.98 3.13 3.899 (2) 136.4 C11—H11···C9_$4 |
Geometry. Specific hydrogen bonds (with e.s.d.'s except fixed and riding H) ============================================================== D—H H···A D···A D—H···A Interaction ============================================================== 0.82 1.82 2.6355 (16) 174.7 O1—H1···O2_$2 0.82 1.94 2.7423 (15) 165.6 O4—H4···O3_$3 0.98 3.06 3.819 (2) 135.7 C11—H11···C4_$4 0.98 2.98 3.829 (2) 146.2 C11—H11···C5_$4 0.98 2.94 3.895 (2) 165.2 C11—H11···C6_$4 0.98 3.01 3.965 (2) 166.2 C11—H11···C7_$4 0.98 3.11 3.977 (2) 147.6 C11—H11···C8_$4 0.98 3.13 3.899 (2) 136.4 C11—H11···C9_$4 0.97 2.48 3.3137 (19) 144.3 C10—H10B···O3_$5 Mean plane data ex-SHELXL97 for molecule (II) ############################################# Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) -3.5887(0.0039)x + 4.5284(0.0118)y + 10.3473(0.0076)z = 3.3296(0.0061) * -0.0029 (0.0004) O1 * -0.0033 (0.0005) O2 * 0.0087 (0.0013) C1 * -0.0024 (0.0004) C2 1.1561 (0.0024) C11 - 0.0322 (0.0025) N1 Rms deviation of fitted atoms = 0.0050 2.6601(0.0034)x + 8.7249(0.0072)y + 8.5511(0.0068)z = 8.3378(0.0016) Angle to previous plane (with approximate e.s.d.) = 65.91 (5) * 0.0001 (0.0010) C4 * -0.0022 (0.0011) C5 * 0.0021 (0.0012) C6 * 0.0002 (0.0012) C7 * -0.0024 (0.0011) C8 * 0.0022 (0.0010) C9 0.0531 (0.0024) N1 - 0.0474 (0.0027) O3 Rms deviation of fitted atoms = 0.0018 2.6745(0.0040)x + 8.9186(0.0077)y + 8.3566(0.0079)z = 8.3457(0.0012) Angle to previous plane (with approximate e.s.d.) = 1.13 (11) * 0.0168 (0.0009) N1 * -0.0159 (0.0008) C3 * 0.0085 (0.0009) C4 * 0.0008 (0.0009) C9 * -0.0103 (0.0008) C10 - 0.0610 (0.0022) O3 - 1.2530 (0.0027) C1 0.0308 (0.0023) C2 Rms deviation of fitted atoms = 0.0120 -3.5887(0.0039)x + 4.5284(0.0118)y + 10.3473(0.0076)z = 3.3296(0.0061) Angle to previous plane (with approximate e.s.d.) = 66.40 (6) * -0.0029 (0.0004) O1 * -0.0033 (0.0005) O2 * 0.0087 (0.0013) C1 * -0.0024 (0.0004) C2 1.1561 (0.0024) C11 - 0.0322 (0.0025) N1 Rms deviation of fitted atoms = 0.0050 1.1393(0.0054)x - 5.4892(0.0277)y + 12.0457(0.0126)z = 7.5545(0.0132) Angle to previous plane (with approximate e.s.d.) = 64.50 (8) * 0.0000 (0.0000) O4 * 0.0000 (0.0000) C11 * 0.0000 (0.0000) C12 - 2.4914 (0.0021) N1 - 1.2374 (0.0035) C2 Rms deviation of fitted atoms = 0.0000 ################################################################ (I) & (II) with DL-phenylalanine (III) and DL-meta-tyrosine (IV) derivatives: A carboxylic acid bond length and angle study ################################################################ (I) L-threonine derivative O1—C1 1.322 (3) O2—C1 1.193 (3) O3—C3 1.232 (3) O1—C1—O2 124.9 (3) O1—C1—C2 109.7 (2) O2—C1—C2 125.4 (3) (II) DL-threonine derivative O1—C1 1.2961 (17) <<< O2—C1 1.2210 (18) <<< O3—C3 1.2350 (17) O1—C1—O2 124.05 (14) O1—C1—C2 113.29 (12) <<< O2—C1—C2 122.63 (13) <<< DL-phenylalanine - CF1250 O1—C1 1.314 (2) O2—C1 1.194 (2) O3—C3 1.239 (2) O1—C1—O2 124.00 (18) O1—C1—C2 112.05 (16) O2—C1—C2 123.95 (18) DL-meta-tyrosine - GD1055 O1—C1 1.328 (2) O2—C1 1.196 (2) O3—C3 1.236 (2) O1—C1—O2 124.3 (2) O1—C1—C2 110.17 (18) O2—C1—C2 125.55 (19) |
x | y | z | Uiso*/Ueq | ||
O1 | 0.7516 (2) | 0.03436 (8) | 0.56714 (10) | 0.0616 (4) | |
O2 | 0.5252 (2) | 0.10744 (8) | 0.45658 (9) | 0.0572 (4) | |
O3 | 1.06897 (17) | 0.26222 (9) | 0.36942 (8) | 0.0515 (3) | |
O4 | 0.64987 (17) | 0.23198 (9) | 0.67140 (7) | 0.0499 (3) | |
N1 | 0.77066 (19) | 0.26700 (8) | 0.46910 (8) | 0.0351 (3) | |
C1 | 0.6886 (3) | 0.10627 (10) | 0.51494 (10) | 0.0391 (4) | |
C2 | 0.8424 (2) | 0.18912 (10) | 0.53093 (10) | 0.0353 (3) | |
C3 | 0.8919 (2) | 0.29767 (10) | 0.39366 (10) | 0.0362 (3) | |
C4 | 0.7708 (2) | 0.37805 (10) | 0.34954 (10) | 0.0374 (3) | |
C5 | 0.8271 (3) | 0.43616 (12) | 0.27247 (11) | 0.0480 (4) | |
C6 | 0.6815 (3) | 0.50705 (12) | 0.24593 (12) | 0.0547 (5) | |
C7 | 0.4848 (3) | 0.51948 (11) | 0.29424 (13) | 0.0549 (5) | |
C8 | 0.4288 (3) | 0.46136 (11) | 0.37064 (12) | 0.0486 (4) | |
C9 | 0.5754 (2) | 0.39037 (10) | 0.39802 (10) | 0.0374 (3) | |
C10 | 0.5612 (2) | 0.31874 (10) | 0.47769 (11) | 0.0394 (4) | |
C11 | 0.8693 (2) | 0.21278 (10) | 0.64189 (10) | 0.0379 (3) | |
C12 | 1.0275 (3) | 0.29277 (12) | 0.66338 (13) | 0.0564 (5) | |
H1 | 0.6621 | −0.0081 | 0.5566 | 0.092* | |
H4 | 0.6496 | 0.2320 | 0.7322 | 0.075* | |
H2 | 0.9903 | 0.1703 | 0.5101 | 0.042* | |
H5 | 0.9587 | 0.4274 | 0.2400 | 0.058* | |
H6 | 0.7155 | 0.5472 | 0.1949 | 0.066* | |
H7 | 0.3887 | 0.5678 | 0.2749 | 0.066* | |
H8 | 0.2965 | 0.4698 | 0.4027 | 0.058* | |
H10A | 0.5545 | 0.3473 | 0.5426 | 0.047* | |
H10B | 0.4316 | 0.2789 | 0.4657 | 0.047* | |
H11 | 0.9267 | 0.1579 | 0.6780 | 0.046* | |
H12A | 1.0305 | 0.3074 | 0.7329 | 0.085* | |
H12B | 0.9774 | 0.3460 | 0.6255 | 0.085* | |
H12C | 1.1753 | 0.2758 | 0.6454 | 0.085* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0779 (9) | 0.0384 (6) | 0.0656 (8) | −0.0105 (6) | −0.0225 (7) | 0.0102 (6) |
O2 | 0.0691 (8) | 0.0410 (7) | 0.0587 (7) | −0.0062 (6) | −0.0216 (6) | 0.0013 (5) |
O3 | 0.0415 (6) | 0.0749 (8) | 0.0393 (6) | 0.0087 (6) | 0.0124 (5) | 0.0118 (5) |
O4 | 0.0493 (6) | 0.0704 (8) | 0.0310 (6) | 0.0003 (6) | 0.0095 (5) | 0.0012 (5) |
N1 | 0.0368 (6) | 0.0383 (7) | 0.0307 (6) | 0.0014 (5) | 0.0076 (5) | 0.0042 (5) |
C1 | 0.0516 (9) | 0.0346 (8) | 0.0308 (7) | 0.0022 (7) | 0.0005 (7) | −0.0017 (6) |
C2 | 0.0383 (8) | 0.0365 (8) | 0.0314 (7) | 0.0019 (6) | 0.0054 (6) | 0.0026 (6) |
C3 | 0.0361 (8) | 0.0452 (9) | 0.0273 (7) | −0.0053 (7) | 0.0023 (6) | −0.0005 (6) |
C4 | 0.0420 (8) | 0.0403 (8) | 0.0298 (7) | −0.0081 (6) | 0.0002 (6) | −0.0001 (6) |
C5 | 0.0543 (9) | 0.0515 (10) | 0.0383 (8) | −0.0105 (8) | 0.0034 (7) | 0.0071 (8) |
C6 | 0.0787 (12) | 0.0436 (9) | 0.0411 (9) | −0.0127 (9) | −0.0020 (9) | 0.0104 (7) |
C7 | 0.0794 (12) | 0.0352 (9) | 0.0486 (10) | 0.0067 (8) | −0.0090 (9) | 0.0002 (7) |
C8 | 0.0570 (10) | 0.0417 (9) | 0.0472 (9) | 0.0069 (8) | 0.0022 (8) | −0.0024 (7) |
C9 | 0.0452 (8) | 0.0344 (8) | 0.0325 (7) | −0.0032 (6) | 0.0007 (6) | −0.0031 (6) |
C10 | 0.0412 (8) | 0.0400 (8) | 0.0377 (8) | 0.0030 (6) | 0.0086 (6) | 0.0021 (7) |
C11 | 0.0412 (8) | 0.0392 (8) | 0.0333 (7) | −0.0031 (7) | 0.0010 (6) | 0.0023 (6) |
C12 | 0.0588 (11) | 0.0554 (11) | 0.0540 (10) | −0.0152 (9) | −0.0059 (8) | −0.0031 (9) |
O1—C1 | 1.2961 (17) | C3—C4 | 1.473 (2) |
O2—C1 | 1.2210 (18) | C4—C5 | 1.390 (2) |
O3—C3 | 1.2350 (17) | C4—C9 | 1.381 (2) |
O4—C11 | 1.4187 (17) | C5—C6 | 1.375 (2) |
N1—C2 | 1.4481 (18) | C6—C7 | 1.387 (3) |
N1—C3 | 1.3552 (17) | C7—C8 | 1.383 (2) |
N1—C10 | 1.4669 (18) | C8—C9 | 1.383 (2) |
C1—C2 | 1.514 (2) | C9—C10 | 1.495 (2) |
C2—C11 | 1.535 (2) | C11—C12 | 1.508 (2) |
C2—N1—C3 | 122.08 (12) | C3—C4—C9 | 108.60 (12) |
C2—N1—C10 | 125.06 (11) | C5—C4—C9 | 121.50 (14) |
C3—N1—C10 | 112.83 (12) | C4—C5—C6 | 117.75 (15) |
O1—C1—O2 | 124.05 (14) | C5—C6—C7 | 120.92 (15) |
O1—C1—C2 | 113.29 (12) | C6—C7—C8 | 121.21 (16) |
O2—C1—C2 | 122.63 (13) | C7—C8—C9 | 118.07 (16) |
N1—C2—C1 | 111.67 (11) | C4—C9—C8 | 120.55 (14) |
N1—C2—C11 | 113.71 (12) | C4—C9—C10 | 109.57 (12) |
C1—C2—C11 | 110.14 (11) | C8—C9—C10 | 129.88 (14) |
O3—C3—N1 | 124.45 (14) | N1—C10—C9 | 102.16 (11) |
O3—C3—C4 | 128.80 (13) | O4—C11—C2 | 105.52 (11) |
N1—C3—C4 | 106.75 (12) | O4—C11—C12 | 112.15 (13) |
C3—C4—C5 | 129.90 (14) | C2—C11—C12 | 112.84 (12) |
C3—N1—C2—C1 | −112.29 (14) | C4—C5—C6—C7 | −0.4 (2) |
C10—N1—C2—C1 | 65.51 (17) | C5—C6—C7—C8 | 0.2 (3) |
C3—N1—C2—C11 | 122.32 (14) | C6—C7—C8—C9 | 0.3 (2) |
C10—N1—C2—C11 | −59.88 (18) | C5—C4—C9—C8 | 0.2 (2) |
O2—C1—C2—N1 | −0.2 (2) | C3—C4—C9—C8 | −179.67 (13) |
O1—C1—C2—N1 | 178.16 (13) | C5—C4—C9—C10 | −179.34 (13) |
O2—C1—C2—C11 | 127.18 (15) | C3—C4—C9—C10 | 0.77 (16) |
O1—C1—C2—C11 | −54.49 (17) | C7—C8—C9—C4 | −0.4 (2) |
C2—N1—C3—O3 | 1.4 (2) | C7—C8—C9—C10 | 179.01 (15) |
C10—N1—C3—O3 | −176.68 (14) | C3—N1—C10—C9 | −2.61 (15) |
C2—N1—C3—C4 | −178.81 (12) | C2—N1—C10—C9 | 179.40 (12) |
C10—N1—C3—C4 | 3.14 (16) | C4—C9—C10—N1 | 0.99 (15) |
O3—C3—C4—C9 | 177.43 (15) | C8—C9—C10—N1 | −178.52 (15) |
N1—C3—C4—C9 | −2.39 (15) | N1—C2—C11—O4 | 66.92 (15) |
O3—C3—C4—C5 | −2.5 (3) | C1—C2—C11—O4 | −59.28 (15) |
N1—C3—C4—C5 | 177.73 (14) | N1—C2—C11—C12 | −55.87 (17) |
C9—C4—C5—C6 | 0.2 (2) | C1—C2—C11—C12 | 177.94 (13) |
C3—C4—C5—C6 | −179.93 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.82 | 1.82 | 2.6355 (16) | 175 |
O4—H4···O3ii | 0.82 | 1.94 | 2.7423 (15) | 166 |
C10—H10B···O3iii | 0.97 | 2.48 | 3.3140 (17) | 144 |
C11—H11···Cg2iv | 0.98 | 2.70 | 3.6440 (16) | 161 |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) x−1/2, −y+1/2, z+1/2; (iii) x−1, y, z; (iv) x+1/2, −y+1/2, z+1/2. |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | C12H13NO4 | C12H13NO4 |
Mr | 235.23 | 235.23 |
Crystal system, space group | Orthorhombic, P212121 | Monoclinic, P21/n |
Temperature (K) | 294 | 294 |
a, b, c (Å) | 6.2209 (6), 11.9726 (13), 15.0705 (12) | 5.9772 (7), 14.3906 (12), 13.4926 (16) |
α, β, γ (°) | 90, 90, 90 | 90, 93.131 (7), 90 |
V (Å3) | 1122.5 (2) | 1158.8 (2) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.10 |
Crystal size (mm) | 0.32 × 0.14 × 0.12 | 0.39 × 0.35 × 0.21 |
Data collection | ||
Diffractometer | Enraf-Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3932, 1967, 1441 | 2242, 2155, 1623 |
Rint | 0.020 | 0.008 |
(sin θ/λ)max (Å−1) | 0.595 | 0.606 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.040, 0.096, 1.01 | 0.034, 0.086, 1.05 |
No. of reflections | 1967 | 2155 |
No. of parameters | 163 | 158 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.16, −0.15 | 0.16, −0.12 |
Absolute structure | Flack (1983) | ? |
Absolute structure parameter | not reliably determined | ? |
Computer programs: CAD-4-PC Software (Enraf-Nonius, 1992), CAD-4-PC Software, NRCVAX96 (Gabe et al., 1989), SHELXS97 (Sheldrick, 1997b), NRCVAX96 and SHELXL97 (Sheldrick, 1997a), ORTEPIII (Burnett & Johnson, 1996), ORTEX (McArdle, 1995) and PLATON (Spek, 1998), NRCVAX96, SHELXL97 and PREP8 (Ferguson, 1998).
O1—C1 | 1.322 (3) | N1—C10 | 1.465 (3) |
O2—C1 | 1.193 (3) | C1—C2 | 1.520 (4) |
O3—C3 | 1.232 (3) | C2—C11 | 1.534 (4) |
O4—C11 | 1.427 (3) | C3—C4 | 1.469 (4) |
N1—C2 | 1.454 (3) | C9—C10 | 1.509 (4) |
N1—C3 | 1.354 (3) | C11—C12 | 1.511 (3) |
C2—N1—C3 | 121.6 (2) | O3—C3—N1 | 125.5 (2) |
C2—N1—C10 | 125.1 (2) | O3—C3—C4 | 127.7 (2) |
C3—N1—C10 | 113.0 (2) | N1—C3—C4 | 106.8 (2) |
O1—C1—O2 | 124.9 (3) | C4—C9—C10 | 109.0 (2) |
O1—C1—C2 | 109.7 (2) | C8—C9—C10 | 131.0 (3) |
O2—C1—C2 | 125.4 (3) | N1—C10—C9 | 102.0 (2) |
N1—C2—C1 | 111.4 (2) | O4—C11—C2 | 110.5 (2) |
N1—C2—C11 | 114.7 (2) | O4—C11—C12 | 111.9 (2) |
C1—C2—C11 | 112.7 (2) | C2—C11—C12 | 112.2 (2) |
C3—N1—C2—C1 | −104.5 (3) | N1—C2—C11—O4 | 78.1 (3) |
O2—C1—C2—N1 | 0.8 (4) | C1—C2—C11—O4 | −50.8 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4i | 0.81 (4) | 1.87 (4) | 2.659 (3) | 162 (4) |
O4—H4···O3ii | 0.82 (4) | 1.90 (4) | 2.718 (3) | 174 (4) |
C10—H10A···O3ii | 0.97 | 2.57 | 3.513 (4) | 165 |
C5—H5···Cg2iii | 0.93 | 2.80 | 3.512 (3) | 134 |
C11—H11···Cg2iv | 0.98 | 2.77 | 3.573 (3) | 140 |
C12—H12C···Cg1iv | 0.96 | 2.84 | 3.672 (3) | 145 |
Symmetry codes: (i) x−1/2, −y+1/2, −z+2; (ii) x+1, y, z; (iii) x−1/2, −y+1/2, −z+1; (iv) −x+1, y−1/2, −z+3/2. |
O1—C1 | 1.2961 (17) | N1—C10 | 1.4669 (18) |
O2—C1 | 1.2210 (18) | C1—C2 | 1.514 (2) |
O3—C3 | 1.2350 (17) | C2—C11 | 1.535 (2) |
O4—C11 | 1.4187 (17) | C3—C4 | 1.473 (2) |
N1—C2 | 1.4481 (18) | C9—C10 | 1.495 (2) |
N1—C3 | 1.3552 (17) | C11—C12 | 1.508 (2) |
C2—N1—C3 | 122.08 (12) | O3—C3—N1 | 124.45 (14) |
C2—N1—C10 | 125.06 (11) | O3—C3—C4 | 128.80 (13) |
C3—N1—C10 | 112.83 (12) | N1—C3—C4 | 106.75 (12) |
O1—C1—O2 | 124.05 (14) | C4—C9—C10 | 109.57 (12) |
O1—C1—C2 | 113.29 (12) | C8—C9—C10 | 129.88 (14) |
O2—C1—C2 | 122.63 (13) | N1—C10—C9 | 102.16 (11) |
N1—C2—C1 | 111.67 (11) | O4—C11—C2 | 105.52 (11) |
N1—C2—C11 | 113.71 (12) | O4—C11—C12 | 112.15 (13) |
C1—C2—C11 | 110.14 (11) | C2—C11—C12 | 112.84 (12) |
C3—N1—C2—C1 | −112.29 (14) | N1—C2—C11—O4 | 66.92 (15) |
O1—C1—C2—N1 | 178.16 (13) | C1—C2—C11—O4 | −59.28 (15) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.82 | 1.82 | 2.6355 (16) | 175 |
O4—H4···O3ii | 0.82 | 1.94 | 2.7423 (15) | 166 |
C10—H10B···O3iii | 0.97 | 2.48 | 3.3140 (17) | 144 |
C11—H11···Cg2iv | 0.98 | 2.70 | 3.6440 (16) | 161 |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) x−1/2, −y+1/2, z+1/2; (iii) x−1, y, z; (iv) x+1/2, −y+1/2, z+1/2. |
The study of biologically active molecules is of primary importance in medicinal chemistry. Many inhibitors are based on modified amino acids which incorporate the basic structural features determining normal enzyme-substrate interactions. Phthalimidine (isoindolin-1-one) derivatives often display biological activity as potential antiinflammatory agents and antipsychotics (Norman et al., 1993; Allin et al., 1996). The majority of structurally determined phthalimidine systems are either N-substituted or substituted at the 3-position (McNab et al., 1997; Kundu et al., 1999). Threonine and its derivatives have attracted considerable interest, not least due to the alkyl hydroxy group which can participate in binding, intermolecular interactions and as a linking group in proteins. The title compounds, (2S/3R)-3-hydroxy-2-(1-oxoisoindolin-2-yl)butanoic acid, (I), and (2R,3S/2S,3R)-3-hydroxy-2-(1-oxoisoindolin-2-yl)butanoic acid, (II), synthesized from the chiral L and racemic DL forms of threonine, respectively, constitute part of a study of the hydrogen-bonding interactions and anion recognition properties of synthetic amino acid derivatives (Brady et al., 1998; Dalton et al., 1999; Gallagher & Murphy, 1999; Gallagher et al., 1999a,b). \scheme
A view of molecule (I) (SR configuration) is shown in Fig. 1 and selected dimensions are in Table 1. Molecule (II) is depicted similarly in Fig. 2, with selected dimensions in Table 3. The bond lengths and angles in the isoindoline group of both structures are similar to those reported previously (McNab et al., 1997; Kundu et al., 1999) and are in agreement with expected values (Orpen et al., 1994). The angles between the five- and six-membered rings of the isoindoline systems are 0.66 (18)° in (I) and 1.13 (11)° in (II), and the maximum deviation from planarity for an atom in either ring plane is 0.0179 (17) Å for N1 in (I) and 0.0168 (9) Å for N1 in (II), with the carbonyl O3 atom 0.071 (4) Å from the C4N ring plane in (I), and 0.061 (2) Å in (II). The carboxylic acid CCO2 plane is almost perpendicular to the C4N ring plane [72.30 (11)° in (I) and 66.40 (6)° in (II)] and to the C12/C11/O4 (H3CCOH) plane [76.5 (2)° in (I) and 64.50 (8)° in (II)].
There are distinct differences in the carboxylic acid bond lengths and angles of (I) and (II). The C—O and C=O bond lengths are 1.322 (3) and 1.193 (3) Å in (I), and 1.2961 (17) and 1.2210 (18) Å in (II), respectively. The O—C—C2 and O=C—C2 angles are 109.7 (2) and 125.4 (3)° in (I), differing considerably from 113.29 (12) and 122.63 (13)° in (II). However, the O=C—O bond angles are similar, at 124.9 (3) and 124.05 (14)°, respectively. This suggests that the differences may be influenced by their different hydrogen-bonding environments (Tables 2 and 4), resulting in a twist in the COOH groups of ca 3°. The carboxylic group geometry in (I) is similar to that reported in a DL-phenylalanine derivative, (III) (Brady et al., 1998) and in a meta-tyrosine derivative, (IV) (Gallagher & Murphy, 1999). The C—O and C=O bond lengths are 1.314 (2) and 1.194 (2), and 1.328 (2), 1.196 (2) Å, in (III) and (IV), respectively, with O—C=O angles of 124.00 (18) and 124.3 (3)° in (III) and (IV), respectively. The O—C—C2 and O=C—C2 angles in (III) and (IV) are intermediate between the values in (I) and (II), at 112.05 (16) and 123.95 (18)° for (III), and 110.17 (18) and 125.55 (19)° for (IV); these values for (IV) are close to those for (I) above.
The indole C=O and hydroxy Csp3—O bond lengths of 1.232 (3) and 1.427 (3) Å, and 1.2350 (17) and 1.4187 (17) Å are similar in (I) and (II), respectively, [1.239 (2) and 1.236 (2) Å for the indole C=O bond lengths in (III) and (IV), respectively]. However, the O4—C11—C2 and C1—C2—C11 angles differ notably, with values of 110.5 (2) and 112.7 (2)° in (I), and 105.52 (11) and 110.14 (11)° in (II), and this is also indicative of dissimilar hydrogen-bonding environments. Torsion angle differences are evident, with N1—C2—C11—O4 = 78.1 (3)° in (I) and 66.92 (15)° in (II), reflecting the different participation of the alkyl O—H group in hydrogen bonding in the two structures.
The hydrogen-bonding arrangements are maximized in both structures and related to those in (III) and (IV) (Brady et al., 1998; Gallagher & Murphy, 1999). The hydrogen bonding in (I) and (II) is dominated by O—H···O, C—H···O and C—H···πarene interactions (Tables 2 and 4, Figs. 3 and 4). The primary hydrogen bonding in (I) involves Oacid—H···Oalkyl—H···O=Cisoindole chains [O···O 2.659 (3) and 2.718 (3) Å], similar to the primary hydrogen-bonded chain in the meta-tyrosine structure (Gallagher & Murphy, 1999), where the O···O distances are 2.668 (2) and 2.653 (2) Å. The O—Hi···O—H···O=Cii chain in (I) forms a one-dimensional network in the a axis direction, with hydrogen-bonded rings [graph set R33(15)] consisting of one alkyl O—H and two acid O—H donors and an indole O=C and two alkyl O—H groups as acceptors between three molecules [symmetry codes: (i) 1/2 + x, 1/2 - y, 2 - z; (ii) 1 + x, y, z]. The C10—H10A···O3ii hydrogen bond [C···O 3.513 (4) Å] further generates a hydrogen-bonded ring system [graph set R12(8)], with an alkyl O—H and a Csp3—H as donors and the indole O=C as an acceptor along the a axis direction [H4···O3ii···H10A 66°]. The carboxylic acid oxygen O2 only forms a weak C—H···O contact in (I). The C—H···πarene interactions complete the intermolecular interactions, forming a three-dimensional network in the crystal structure of (I) with two (C11—H11/C12—H12C)···πindole contacts participating in a relay of C—H···πarene interactions.
Compound (II) shows some interesting differences to (I). Classical COOH hydrogen bonding arises [to form dimers; graph set R22(8)] about inversion centres as cyclical O—H···O=C hydrogen bonds involving both O1 and O2 (Ferguson et al., 1995). The alkyl hydroxy group O4—H···O=C3 links these dimers to form a two-dimensional network, as depicted in Fig. 4. Weaker C—H···O=Cindole and Csp3—H···πarene interactions complete the hydrogen bonding, thus forming a three-dimensional network. The contrast in the carboxylic acid geometry between (I) and (II) can be explained by the dissimilar participation of O2 in the hydrogen bonding. The primary COOH hydrogen bonding in (II) [graph set R22(8)] differs from that reported in the DL-phenylalanine structure (III), where pairwise intermolecular Oacid—H···Oindole and Carene—H···Ocarboxylate interactions form a hydrogen-bonded ring [graph set R22(9)], and from that in the structures of (I) and DL-meta-tyrosine (IV), which contain Oacid—H···O—H···O=Cindole chains.
The volumes per atom in (I) and (II) differ, with a value of 16.51 Å3 per non-H atom for (I) and 17.04 Å3 for (II), reflecting differing packing considerations and the extra interactions present in (I). Examination of the structures with PLATON (Spek, 1998) shows that there are no solvent accessible voids in either crystal lattice.
Crystal engineering studies continue to rely on stronger hydrogen bonds for the design and synthesis of three-dimensional structures (Aakeröy et al., 1999). However, a thorough understanding of the control and exploitation of X—H···πarene interactions (X = C, N or O) remains an elusive goal (Braga et al., 1998). Theoretical calculations on C—H···πarene interactions have been reported in several organic systems, including an estimation of the binding energy between the C—H donor and the aromatic π cloud (Samanta et al., 1998), as well as database studies (Malone et al., 1997). The role of such interactions in biological structures has also been detailed by Umezawa & Nishio (1998). However, in (I) and (II), the primary hydrogen bonding is considered prior to analysis of the weaker interactions. The stronger hydrogen bonds form a primary array which is linked into networks by the weaker interactions in both structures. Further comparative studies are in progress on related phthalimidines.