organic compounds
N-(Fluoren-9-ylmethoxycarbonyl)-L-aspartic acid 4-tert-butyl ester
aNational Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan, and bAdvanced Technology Support Division, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
*Correspondence e-mail: yamada.kazuhiko@nims.go.jp
The bond distances and bond angles of the title compound, C23H25NO6, are consistent with values typically found for fluoren-9-ylmethoxycarbonyl-protected amino acids. The conformations of the backbone and the side chain are slightly different from those of L-aspartic acid. The exhibits two intermolecular hydrogen bonds, forming a two-dimensional sheet structure parallel to the ab plane.
Related literature
For the crystal structures of aspartic acids, see: Dawson (1977); Sequeira et al. (1989); Flaig et al. (1998); Rao (1973); Wang et al. (2007); Umadevi et al. (2003); Derissen et al. (1968); Bendeif & Jelsch (2007). For the crystal structures of N-α-fluoren-9-ylmethoxycarbonyl-protected amino acids, see: Valle et al. (1984); Yamada, Hashizume & Shimizu (2008); Yamada, Hashizume, Shimizu & Deguchi (2008); Yamada, Hashizume, Shimizu, Ohiki & Yokoyama (2008).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: CrystalClear (Rigaku/MSC, 2005); cell HKL-2000 (Otwinowski & Minor, 1997); data reduction: HKL-2000; program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
Supporting information
https://doi.org/10.1107/S1600536809037611/fj2243sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536809037611/fj2243Isup2.hkl
A powdered sample of the title compound was purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Single crystals suitable for X-ray structure analysis could be obtained by recrystallization from ethyl acetate-dichloromethane (80:20) solution, which afforded white needle-like crystals.
All H atoms were located on the difference maps, and were treated as riding atoms with C/N/O–H distances of 1.00, 0.99, 0.98, 0.95, 0.88 and 0.84 Å, for methyne, methylene, methyl, phenyl, amino and hydroxyl groups, respectively, on the refinements. The Uiso's of the H atoms were fixed to be 1.2Ueq(C/N) for methyne, methylene, phenyl and amino, or 1.5Ueq(C/O) for methyl and hydroxyl of the parent atoms.
All Friedel pairs were merged, and all f"s of containing atoms were set to zero.
L-Aspartic acid is one of the 20 building blocks of proteins, and, in mammals, can be produced from oxaloacetate by transamination. As for the related compounds of an aspartic acid, the crystal structures of L-aspartic acid (Derissen et al.,1968; Bendeif & Jelsch, 2007), L-aspartic acid monohydrate (Umadevi et al., 2003), DL-aspartic acid (Sequeira et al., 1989; Flaig et al., 1998; Rao, 1973; Wang et al., 2007), and DL-aspartic acid hydrochloride (Dawson, 1977) have been reported so far.
Fluoren-9-ylmethoxycarbonyl (Fmoc) group is widely used for solid-phase peptide synthesis protocols as an N-α-protecting group. To our best knowledge, however,there have been only four literatures reporting crystal structures of Fmoc-protected amino acids (Valle et al., 1984; Yamada, Hashizume & Shimizu, 2008; Yamada, Hashizume, Shimizu & Deguchi, 2008; Yamada, Hashizume, Shimizu, Ohiki & Yokoyama, 2008). In this communication, the of N-Fmoc-protected aspartic acid 4-tert-butyl ester (I) is reported.
The molecular structure of (I) is shown in Fig. 1 together with the atom labeling. The bond lengths and angles of the present molecule are in reasonable agreement with typical values found in L-aspartic acids and the related compounds. The conformations of the backbone and the side-chain, however, are slightly different from those of L-aspartic acid. The torsion angles, N1–C1–C2–C3 and N1–C1–C4–O4, are found to be 62.5 (4) and 17.0 (5)°, respectively. For L-aspartic acid, the corresponding angles are -60.3 and -39.2°, respectively. In the Fmoc-protected amino acids, the fluoren moiety takes various conformations as shown in the available literatures. In this case, the conformation of the Fmoc moiety is similar to those of Fmoc-protected isoleucine and serine.
Fig. 2 shows the
of (I). The molecules are linked via intermolecular hydrogen bonds between carboxyl and Fmoc moieties, O3–H3···O5 to form the column around the 21 screw axis parallel to the b axis. The columns, related by translation symmeties along the a axis each other, are joined together through weak hydrogen bonds between the amino and carboxyl groups, N1—H1···O3, two-dimensional sheet structures are formed paralell to the ab plane consequentry. The geometries of the hydrogen bonds are listed in Table 2.For related literature on the crystal structures of aspartic acids, see: Dawson (1977); Sequeira et al. (1989); Flaig et al. (1998); Rao (1973); Wang et al. (2007); Umadevi et al. (2003); Derissen et al. (1968); Bendeif & Jelsch (2007). For related literature on the crystal structures of N-α-fluoren-9-ylmethoxycarbonyl-protected amino acids, see: Valle et al. (1984); Yamada, Hashizume & Shimizu (2008); Yamada, Hashizume, Shimizu & Deguchi (2008); Yamada, Hashizume, Shimizu, Ohiki & Yokoyama (2008).
Data collection: CrystalClear (Rigaku/MSC, 2005); cell
HKL-2000 (Otwinowski & Minor, 1997); data reduction: HKL-2000 (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C23H25NO6 | F(000) = 872 |
Mr = 411.44 | Dx = 1.340 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 15181 reflections |
a = 5.7166 (4) Å | θ = 1.8–27.6° |
b = 11.1175 (10) Å | µ = 0.10 mm−1 |
c = 32.083 (3) Å | T = 90 K |
V = 2039.0 (3) Å3 | Needle, colourless |
Z = 4 | 0.11 × 0.05 × 0.04 mm |
Rigaku AFC-8 diffractometer with Saturn70 CCD detector | 2167 reflections with I > 2σ(I) |
Radiation source: fine-focus rotating anode | Rint = 0.077 |
Confocal monochromator | θmax = 27.6°, θmin = 1.9° |
Detector resolution: 28.5714 pixels mm-1 | h = −7→6 |
ω scans | k = −14→10 |
15110 measured reflections | l = −41→41 |
2722 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.059 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.148 | H-atom parameters constrained |
S = 1.13 | w = 1/[σ2(Fo2) + (0.0694P)2 + 0.981P] where P = (Fo2 + 2Fc2)/3 |
2722 reflections | (Δ/σ)max < 0.001 |
286 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.27 e Å−3 |
C23H25NO6 | V = 2039.0 (3) Å3 |
Mr = 411.44 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 5.7166 (4) Å | µ = 0.10 mm−1 |
b = 11.1175 (10) Å | T = 90 K |
c = 32.083 (3) Å | 0.11 × 0.05 × 0.04 mm |
Rigaku AFC-8 diffractometer with Saturn70 CCD detector | 2167 reflections with I > 2σ(I) |
15110 measured reflections | Rint = 0.077 |
2722 independent reflections |
R[F2 > 2σ(F2)] = 0.059 | 0 restraints |
wR(F2) = 0.148 | H-atom parameters constrained |
S = 1.13 | Δρmax = 0.29 e Å−3 |
2722 reflections | Δρmin = −0.27 e Å−3 |
286 parameters |
Experimental. All Friedel pairs were merged, and all f"s of containing atoms were set to zero. |
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. |
Refinement. Refinement of F2 against al reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on all data will be even larger. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.6301 (5) | 0.4494 (2) | 0.15286 (8) | 0.0271 (6) | |
O2 | 0.7666 (5) | 0.3298 (2) | 0.10086 (7) | 0.0237 (6) | |
O3 | 1.1545 (5) | 0.4557 (2) | 0.20322 (8) | 0.0254 (6) | |
H3 | 1.2064 | 0.5245 | 0.2089 | 0.038* | |
O4 | 0.8720 (5) | 0.5069 (2) | 0.24884 (8) | 0.0267 (6) | |
O5 | 0.6813 (5) | 0.1857 (2) | 0.28643 (7) | 0.0230 (6) | |
O6 | 0.3240 (5) | 0.2717 (2) | 0.27449 (7) | 0.0207 (6) | |
N1 | 0.6108 (6) | 0.3053 (3) | 0.22971 (9) | 0.0221 (7) | |
H1 | 0.5004 | 0.3395 | 0.2147 | 0.027* | |
C1 | 0.8504 (7) | 0.3115 (3) | 0.21511 (11) | 0.0203 (8) | |
H1A | 0.9431 | 0.2511 | 0.2313 | 0.024* | |
C2 | 0.8711 (7) | 0.2786 (3) | 0.16889 (11) | 0.0221 (8) | |
H2A | 1.0385 | 0.2787 | 0.1610 | 0.027* | |
H2B | 0.8106 | 0.1961 | 0.1648 | 0.027* | |
C3 | 0.7406 (7) | 0.3629 (3) | 0.14049 (11) | 0.0205 (8) | |
C4 | 0.9549 (7) | 0.4366 (3) | 0.22432 (11) | 0.0215 (8) | |
C5 | 0.6574 (8) | 0.4001 (3) | 0.06656 (11) | 0.0254 (9) | |
C6 | 0.7397 (9) | 0.3306 (4) | 0.02814 (12) | 0.0363 (11) | |
H6A | 0.6839 | 0.2474 | 0.0298 | 0.054* | |
H6B | 0.9110 | 0.3312 | 0.0270 | 0.054* | |
H6C | 0.6768 | 0.3687 | 0.0030 | 0.054* | |
C7 | 0.7598 (8) | 0.5265 (3) | 0.06653 (13) | 0.0309 (9) | |
H7A | 0.9308 | 0.5216 | 0.0676 | 0.046* | |
H7B | 0.7024 | 0.5706 | 0.0909 | 0.046* | |
H7C | 0.7120 | 0.5685 | 0.0411 | 0.046* | |
C8 | 0.3951 (8) | 0.3978 (4) | 0.07039 (14) | 0.0333 (10) | |
H8A | 0.3481 | 0.4396 | 0.0959 | 0.050* | |
H8B | 0.3410 | 0.3142 | 0.0715 | 0.050* | |
H8C | 0.3253 | 0.4381 | 0.0462 | 0.050* | |
C9 | 0.5502 (7) | 0.2491 (3) | 0.26529 (11) | 0.0180 (7) | |
C10 | 0.2379 (7) | 0.2366 (3) | 0.31542 (10) | 0.0206 (8) | |
H10A | 0.3663 | 0.2015 | 0.3322 | 0.025* | |
H10B | 0.1125 | 0.1758 | 0.3126 | 0.025* | |
C11 | 0.1424 (7) | 0.3503 (3) | 0.33673 (11) | 0.0199 (8) | |
H11 | 0.0232 | 0.3901 | 0.3185 | 0.024* | |
C12 | 0.0379 (7) | 0.3219 (3) | 0.37912 (11) | 0.0231 (8) | |
C13 | −0.1547 (8) | 0.2505 (3) | 0.38905 (11) | 0.0243 (8) | |
H13 | −0.2397 | 0.2099 | 0.3679 | 0.029* | |
C14 | −0.2195 (7) | 0.2401 (3) | 0.43060 (12) | 0.0263 (9) | |
H14 | −0.3507 | 0.1918 | 0.4378 | 0.032* | |
C15 | −0.0960 (8) | 0.2990 (3) | 0.46202 (12) | 0.0284 (9) | |
H15 | −0.1433 | 0.2903 | 0.4902 | 0.034* | |
C16 | 0.0969 (7) | 0.3707 (3) | 0.45224 (12) | 0.0261 (9) | |
H16 | 0.1830 | 0.4103 | 0.4735 | 0.031* | |
C17 | 0.1598 (8) | 0.3825 (3) | 0.41070 (11) | 0.0227 (8) | |
C18 | 0.3500 (7) | 0.4533 (3) | 0.39111 (11) | 0.0220 (8) | |
C19 | 0.5228 (8) | 0.5253 (3) | 0.40880 (12) | 0.0286 (9) | |
H19 | 0.5306 | 0.5365 | 0.4381 | 0.034* | |
C20 | 0.6843 (8) | 0.5807 (3) | 0.38242 (13) | 0.0302 (10) | |
H20 | 0.8067 | 0.6279 | 0.3940 | 0.036* | |
C21 | 0.6685 (8) | 0.5678 (3) | 0.33946 (13) | 0.0289 (9) | |
H21 | 0.7788 | 0.6072 | 0.3220 | 0.035* | |
C22 | 0.4919 (8) | 0.4973 (3) | 0.32146 (12) | 0.0250 (8) | |
H22 | 0.4792 | 0.4901 | 0.2920 | 0.030* | |
C23 | 0.3357 (7) | 0.4382 (3) | 0.34766 (11) | 0.0230 (8) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0316 (17) | 0.0205 (13) | 0.0293 (14) | 0.0069 (13) | 0.0030 (13) | 0.0004 (10) |
O2 | 0.0291 (16) | 0.0162 (12) | 0.0258 (13) | 0.0015 (12) | −0.0022 (12) | 0.0003 (10) |
O3 | 0.0280 (16) | 0.0139 (12) | 0.0342 (14) | −0.0014 (12) | 0.0038 (13) | 0.0000 (10) |
O4 | 0.0299 (17) | 0.0195 (12) | 0.0306 (13) | 0.0004 (13) | 0.0039 (13) | −0.0027 (11) |
O5 | 0.0225 (14) | 0.0157 (12) | 0.0307 (13) | 0.0032 (11) | 0.0002 (12) | 0.0030 (10) |
O6 | 0.0205 (14) | 0.0179 (12) | 0.0237 (12) | −0.0001 (11) | −0.0007 (11) | 0.0004 (9) |
N1 | 0.0208 (18) | 0.0186 (15) | 0.0269 (15) | 0.0018 (14) | −0.0007 (13) | 0.0030 (12) |
C1 | 0.0191 (19) | 0.0139 (16) | 0.0279 (18) | 0.0013 (16) | −0.0016 (16) | 0.0020 (13) |
C2 | 0.024 (2) | 0.0115 (16) | 0.0305 (18) | 0.0027 (15) | 0.0019 (17) | 0.0004 (13) |
C3 | 0.0168 (19) | 0.0160 (17) | 0.0286 (19) | −0.0019 (15) | 0.0021 (16) | 0.0032 (14) |
C4 | 0.023 (2) | 0.0199 (17) | 0.0212 (17) | 0.0022 (16) | −0.0020 (16) | 0.0023 (14) |
C5 | 0.029 (2) | 0.0225 (18) | 0.0248 (18) | −0.0006 (17) | −0.0020 (19) | 0.0034 (14) |
C6 | 0.041 (3) | 0.037 (2) | 0.031 (2) | 0.003 (2) | −0.001 (2) | −0.0055 (18) |
C7 | 0.031 (2) | 0.0233 (19) | 0.039 (2) | 0.0000 (18) | −0.003 (2) | 0.0060 (16) |
C8 | 0.024 (2) | 0.031 (2) | 0.045 (2) | −0.0005 (18) | −0.007 (2) | 0.0090 (19) |
C9 | 0.0171 (18) | 0.0119 (16) | 0.0249 (17) | −0.0016 (14) | −0.0015 (15) | −0.0022 (13) |
C10 | 0.0212 (19) | 0.0169 (16) | 0.0236 (17) | 0.0028 (15) | 0.0000 (16) | 0.0004 (13) |
C11 | 0.021 (2) | 0.0133 (16) | 0.0260 (17) | 0.0008 (16) | 0.0001 (17) | 0.0016 (13) |
C12 | 0.028 (2) | 0.0135 (16) | 0.0278 (18) | 0.0033 (16) | 0.0004 (17) | 0.0006 (14) |
C13 | 0.025 (2) | 0.0162 (17) | 0.0316 (19) | 0.0022 (17) | −0.0024 (18) | −0.0024 (14) |
C14 | 0.024 (2) | 0.0176 (17) | 0.037 (2) | 0.0013 (16) | 0.0061 (18) | −0.0002 (15) |
C15 | 0.038 (3) | 0.0202 (19) | 0.0270 (19) | 0.0022 (18) | 0.0056 (18) | 0.0016 (14) |
C16 | 0.030 (2) | 0.0175 (18) | 0.031 (2) | 0.0028 (17) | −0.0008 (18) | −0.0040 (14) |
C17 | 0.024 (2) | 0.0139 (16) | 0.0305 (19) | 0.0019 (16) | −0.0001 (17) | −0.0002 (13) |
C18 | 0.020 (2) | 0.0140 (16) | 0.0317 (19) | 0.0006 (16) | 0.0002 (17) | −0.0017 (13) |
C19 | 0.034 (3) | 0.0188 (18) | 0.033 (2) | −0.0009 (17) | −0.0024 (19) | −0.0046 (15) |
C20 | 0.030 (2) | 0.0152 (18) | 0.045 (2) | −0.0057 (17) | −0.001 (2) | −0.0088 (15) |
C21 | 0.030 (2) | 0.0138 (17) | 0.043 (2) | −0.0010 (17) | 0.008 (2) | −0.0010 (15) |
C22 | 0.029 (2) | 0.0131 (16) | 0.0326 (19) | −0.0014 (17) | 0.0021 (18) | −0.0015 (14) |
C23 | 0.022 (2) | 0.0122 (16) | 0.035 (2) | 0.0020 (16) | 0.0013 (18) | 0.0005 (13) |
O1—C3 | 1.218 (4) | C8—H8C | 0.9800 |
O2—C3 | 1.332 (4) | C10—C11 | 1.537 (5) |
O2—C5 | 1.487 (4) | C10—H10A | 0.9900 |
O3—C4 | 1.344 (5) | C10—H10B | 0.9900 |
O3—H3 | 0.8400 | C11—C23 | 1.516 (5) |
O4—C4 | 1.206 (4) | C11—C12 | 1.518 (5) |
O5—C9 | 1.232 (4) | C11—H11 | 1.0000 |
O6—C9 | 1.350 (5) | C12—C13 | 1.395 (6) |
O6—C10 | 1.456 (4) | C12—C17 | 1.402 (5) |
N1—C9 | 1.346 (4) | C13—C14 | 1.388 (5) |
N1—C1 | 1.450 (5) | C13—H13 | 0.9500 |
N1—H1 | 0.8800 | C14—C15 | 1.394 (6) |
C1—C2 | 1.532 (5) | C14—H14 | 0.9500 |
C1—C4 | 1.542 (5) | C15—C16 | 1.397 (6) |
C1—H1A | 1.0000 | C15—H15 | 0.9500 |
C2—C3 | 1.504 (5) | C16—C17 | 1.387 (5) |
C2—H2A | 0.9900 | C16—H16 | 0.9500 |
C2—H2B | 0.9900 | C17—C18 | 1.482 (5) |
C5—C8 | 1.504 (6) | C18—C19 | 1.392 (5) |
C5—C7 | 1.522 (5) | C18—C23 | 1.407 (5) |
C5—C6 | 1.529 (5) | C19—C20 | 1.395 (6) |
C6—H6A | 0.9800 | C19—H19 | 0.9500 |
C6—H6B | 0.9800 | C20—C21 | 1.389 (6) |
C6—H6C | 0.9800 | C20—H20 | 0.9500 |
C7—H7A | 0.9800 | C21—C22 | 1.402 (6) |
C7—H7B | 0.9800 | C21—H21 | 0.9500 |
C7—H7C | 0.9800 | C22—C23 | 1.392 (5) |
C8—H8A | 0.9800 | C22—H22 | 0.9500 |
C8—H8B | 0.9800 | ||
C3—O2—C5 | 120.9 (3) | N1—C9—O6 | 110.2 (3) |
C4—O3—H3 | 109.5 | O6—C10—C11 | 107.5 (3) |
C9—O6—C10 | 118.1 (3) | O6—C10—H10A | 110.2 |
C9—N1—C1 | 122.6 (3) | C11—C10—H10A | 110.2 |
C9—N1—H1 | 118.7 | O6—C10—H10B | 110.2 |
C1—N1—H1 | 118.7 | C11—C10—H10B | 110.2 |
N1—C1—C2 | 112.0 (3) | H10A—C10—H10B | 108.5 |
N1—C1—C4 | 110.3 (3) | C23—C11—C12 | 102.3 (3) |
C2—C1—C4 | 111.7 (3) | C23—C11—C10 | 112.0 (3) |
N1—C1—H1A | 107.5 | C12—C11—C10 | 111.5 (3) |
C2—C1—H1A | 107.5 | C23—C11—H11 | 110.3 |
C4—C1—H1A | 107.5 | C12—C11—H11 | 110.3 |
C3—C2—C1 | 113.6 (3) | C10—C11—H11 | 110.3 |
C3—C2—H2A | 108.9 | C13—C12—C17 | 120.1 (3) |
C1—C2—H2A | 108.9 | C13—C12—C11 | 129.3 (3) |
C3—C2—H2B | 108.9 | C17—C12—C11 | 110.6 (3) |
C1—C2—H2B | 108.9 | C14—C13—C12 | 118.5 (4) |
H2A—C2—H2B | 107.7 | C14—C13—H13 | 120.7 |
O1—C3—O2 | 126.0 (3) | C12—C13—H13 | 120.7 |
O1—C3—C2 | 123.5 (3) | C13—C14—C15 | 121.3 (4) |
O2—C3—C2 | 110.5 (3) | C13—C14—H14 | 119.3 |
O4—C4—O3 | 124.1 (3) | C15—C14—H14 | 119.3 |
O4—C4—C1 | 123.8 (4) | C14—C15—C16 | 120.4 (4) |
O3—C4—C1 | 112.0 (3) | C14—C15—H15 | 119.8 |
O2—C5—C8 | 110.4 (3) | C16—C15—H15 | 119.8 |
O2—C5—C7 | 108.9 (3) | C17—C16—C15 | 118.4 (4) |
C8—C5—C7 | 113.5 (4) | C17—C16—H16 | 120.8 |
O2—C5—C6 | 101.6 (3) | C15—C16—H16 | 120.8 |
C8—C5—C6 | 111.3 (4) | C16—C17—C12 | 121.3 (4) |
C7—C5—C6 | 110.3 (3) | C16—C17—C18 | 130.4 (4) |
C5—C6—H6A | 109.5 | C12—C17—C18 | 108.3 (3) |
C5—C6—H6B | 109.5 | C19—C18—C23 | 120.9 (4) |
H6A—C6—H6B | 109.5 | C19—C18—C17 | 130.8 (3) |
C5—C6—H6C | 109.5 | C23—C18—C17 | 108.3 (3) |
H6A—C6—H6C | 109.5 | C18—C19—C20 | 118.4 (4) |
H6B—C6—H6C | 109.5 | C18—C19—H19 | 120.8 |
C5—C7—H7A | 109.5 | C20—C19—H19 | 120.8 |
C5—C7—H7B | 109.5 | C21—C20—C19 | 120.9 (4) |
H7A—C7—H7B | 109.5 | C21—C20—H20 | 119.6 |
C5—C7—H7C | 109.5 | C19—C20—H20 | 119.6 |
H7A—C7—H7C | 109.5 | C20—C21—C22 | 120.9 (4) |
H7B—C7—H7C | 109.5 | C20—C21—H21 | 119.6 |
C5—C8—H8A | 109.5 | C22—C21—H21 | 119.6 |
C5—C8—H8B | 109.5 | C23—C22—C21 | 118.5 (4) |
H8A—C8—H8B | 109.5 | C23—C22—H22 | 120.7 |
C5—C8—H8C | 109.5 | C21—C22—H22 | 120.7 |
H8A—C8—H8C | 109.5 | C22—C23—C18 | 120.3 (4) |
H8B—C8—H8C | 109.5 | C22—C23—C11 | 129.2 (3) |
O5—C9—N1 | 125.1 (4) | C18—C23—C11 | 110.4 (3) |
O5—C9—O6 | 124.7 (3) | ||
C9—N1—C1—C2 | 132.6 (3) | C12—C13—C14—C15 | −0.2 (6) |
C9—N1—C1—C4 | −102.3 (4) | C13—C14—C15—C16 | 0.2 (6) |
N1—C1—C2—C3 | 62.5 (4) | C14—C15—C16—C17 | 0.7 (6) |
C4—C1—C2—C3 | −61.9 (4) | C15—C16—C17—C12 | −1.6 (6) |
C5—O2—C3—O1 | 0.3 (6) | C15—C16—C17—C18 | 178.6 (4) |
C5—O2—C3—C2 | −179.0 (3) | C13—C12—C17—C16 | 1.7 (6) |
C1—C2—C3—O1 | 0.5 (5) | C11—C12—C17—C16 | −179.9 (4) |
C1—C2—C3—O2 | 179.7 (3) | C13—C12—C17—C18 | −178.5 (3) |
N1—C1—C4—O4 | 17.0 (5) | C11—C12—C17—C18 | −0.1 (4) |
C2—C1—C4—O4 | 142.3 (4) | C16—C17—C18—C19 | 1.9 (7) |
N1—C1—C4—O3 | −165.8 (3) | C12—C17—C18—C19 | −177.9 (4) |
C2—C1—C4—O3 | −40.5 (4) | C16—C17—C18—C23 | −178.1 (4) |
C3—O2—C5—C8 | −63.1 (4) | C12—C17—C18—C23 | 2.1 (4) |
C3—O2—C5—C7 | 62.2 (5) | C23—C18—C19—C20 | −1.0 (6) |
C3—O2—C5—C6 | 178.7 (3) | C17—C18—C19—C20 | 178.9 (4) |
C1—N1—C9—O5 | −9.2 (5) | C18—C19—C20—C21 | 2.2 (6) |
C1—N1—C9—O6 | 171.1 (3) | C19—C20—C21—C22 | −1.0 (6) |
C10—O6—C9—O5 | 10.9 (5) | C20—C21—C22—C23 | −1.5 (6) |
C10—O6—C9—N1 | −169.3 (3) | C21—C22—C23—C18 | 2.6 (6) |
C9—O6—C10—C11 | 122.3 (3) | C21—C22—C23—C11 | −175.1 (4) |
O6—C10—C11—C23 | −68.6 (4) | C19—C18—C23—C22 | −1.4 (6) |
O6—C10—C11—C12 | 177.4 (3) | C17—C18—C23—C22 | 178.7 (3) |
C23—C11—C12—C13 | 176.5 (4) | C19—C18—C23—C11 | 176.7 (3) |
C10—C11—C12—C13 | −63.7 (5) | C17—C18—C23—C11 | −3.2 (4) |
C23—C11—C12—C17 | −1.7 (4) | C12—C11—C23—C22 | −179.1 (4) |
C10—C11—C12—C17 | 118.1 (4) | C10—C11—C23—C22 | 61.3 (5) |
C17—C12—C13—C14 | −0.8 (5) | C12—C11—C23—C18 | 3.0 (4) |
C11—C12—C13—C14 | −178.8 (4) | C10—C11—C23—C18 | −116.5 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O5i | 0.84 | 1.91 | 2.744 (3) | 172 |
N1—H1···O3ii | 0.88 | 2.39 | 3.213 (4) | 156 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x−1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C23H25NO6 |
Mr | 411.44 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 90 |
a, b, c (Å) | 5.7166 (4), 11.1175 (10), 32.083 (3) |
V (Å3) | 2039.0 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.11 × 0.05 × 0.04 |
Data collection | |
Diffractometer | Rigaku AFC-8 diffractometer with Saturn70 CCD detector |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 15110, 2722, 2167 |
Rint | 0.077 |
(sin θ/λ)max (Å−1) | 0.651 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.059, 0.148, 1.13 |
No. of reflections | 2722 |
No. of parameters | 286 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.27 |
Computer programs: CrystalClear (Rigaku/MSC, 2005), HKL-2000 (Otwinowski & Minor, 1997), SIR2004 (Burla et al., 2005), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997).
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O5i | 0.84 | 1.91 | 2.744 (3) | 171.7 |
N1—H1···O3ii | 0.88 | 2.39 | 3.213 (4) | 155.7 |
Symmetry codes: (i) −x+2, y+1/2, −z+1/2; (ii) x−1, y, z. |
Footnotes
‡Present address: Department of Chemistry and Materials Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, Japan.
Acknowledgements
KY thanks the Ministry of Education, Science, Sports, Culture and Technology (MEXT) of Japan for funding this work [Young Scientists (B), grant No. 20750022]. TS appreciates support from the World Premier International Research Center Initiative (WPI Initiative) on Materials Nanoarchitronics (MANA) at NIMS, from MEXT.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
L-Aspartic acid is one of the 20 building blocks of proteins, and, in mammals, can be produced from oxaloacetate by transamination. As for the related compounds of an aspartic acid, the crystal structures of L-aspartic acid (Derissen et al.,1968; Bendeif & Jelsch, 2007), L-aspartic acid monohydrate (Umadevi et al., 2003), DL-aspartic acid (Sequeira et al., 1989; Flaig et al., 1998; Rao, 1973; Wang et al., 2007), and DL-aspartic acid hydrochloride (Dawson, 1977) have been reported so far.
Fluoren-9-ylmethoxycarbonyl (Fmoc) group is widely used for solid-phase peptide synthesis protocols as an N-α-protecting group. To our best knowledge, however,there have been only four literatures reporting crystal structures of Fmoc-protected amino acids (Valle et al., 1984; Yamada, Hashizume & Shimizu, 2008; Yamada, Hashizume, Shimizu & Deguchi, 2008; Yamada, Hashizume, Shimizu, Ohiki & Yokoyama, 2008). In this communication, the crystal structure of N-Fmoc-protected aspartic acid 4-tert-butyl ester (I) is reported.
The molecular structure of (I) is shown in Fig. 1 together with the atom labeling. The bond lengths and angles of the present molecule are in reasonable agreement with typical values found in L-aspartic acids and the related compounds. The conformations of the backbone and the side-chain, however, are slightly different from those of L-aspartic acid. The torsion angles, N1–C1–C2–C3 and N1–C1–C4–O4, are found to be 62.5 (4) and 17.0 (5)°, respectively. For L-aspartic acid, the corresponding angles are -60.3 and -39.2°, respectively. In the Fmoc-protected amino acids, the fluoren moiety takes various conformations as shown in the available literatures. In this case, the conformation of the Fmoc moiety is similar to those of Fmoc-protected isoleucine and serine.
Fig. 2 shows the crystal structure of (I). The molecules are linked via intermolecular hydrogen bonds between carboxyl and Fmoc moieties, O3–H3···O5 to form the column around the 21 screw axis parallel to the b axis. The columns, related by translation symmeties along the a axis each other, are joined together through weak hydrogen bonds between the amino and carboxyl groups, N1—H1···O3, two-dimensional sheet structures are formed paralell to the ab plane consequentry. The geometries of the hydrogen bonds are listed in Table 2.