research communications
O-benzyl-L-tyrosine N-carboxy anhydride
ofaFaculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan
*Correspondence e-mail: kana@sss.fukushima-u.ac.jp
In the title compound, C17H15NO4 (alternative name; O-benzyl-L-tyrosine N-carboxy anhydride), the oxazolidine ring is planer, with an r.m.s. deviation of 0.039 Å. The benzyloxy and benzyl rings are almost coplanar, making a dihedral angle of 0.078 (10)°, and are inclined to the oxazolidine ring by 59.16 (11) and 58.42 (11)°, respectively. In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming ribbons propagating along [010]. The ribbons are linked by C—H⋯π interactions, forming a three-dimensional supramolecular structure. The oxazolidine rings of adjacent ribbons are arranged into a layer parallel to the ab plane. This arrangement is favourable for the polymerization of the compound in the solid state.
Keywords: crystal structure; L-tyrosine; L-amino acid N-carboxy anhydride; O-benzyl-L-tyrosine NCA; solid-state polymerization; hydrogen bonding; C—H⋯π interactions.
CCDC reference: 1538344
1. Chemical context
N-Carboxy (NCAs) of amino acids are extensively used as monomers for the preparation of high molecular weight (Kricheldorf, 2006). Amino acid NCAs are easily soluble but the resulting are not soluble in general organic solvents. Only a few amino acid ester NCAs such as γ-benzyl-L-glutamate NCA (BLG NCA) and β-benzyl-L-aspartate NCA (BLA NCA) are polymerized in solutions, because the resulting are soluble in them. On the other hand, we found that every amino acid NCA crystal is polymerized in the solid state in hexane by the initiation of We studied the polymerization of BLA NCA (Kanazawa & Sato, 1996) and β-benzyl-DL-aspartate NCA (BDLA NCA) initiated by a primary amine in the solution and solid states, and we determined the of BLA NCA (Kanazawa & Magoshi, 2003) and BDLA NCA (Kanazawa & Inada, 2017) to consider their high reactivity in the solid state. In addition, we prepared single crystals of the title compound, O-benzyl-L-tyrosine (OBLT NCA) in hexane–ethyl acetate mixture. The polymerization of OBLT NCA is initiated by butyl amine initiator in dioxane or acetonitrile solutions. However, the polymerization rate was extremely slow, because the resultant polymer has a poor solubility in these solvents. On the other hand, the polymerization of OBLT NCA initiated by butyl amine was very reactive in the solid state in hexane. High molecular weight poly(OBLT) was obtained only in the solid-state polymerization. High molecular weight poly(OBLT) is valuable, because poly(L-tyrosine) is obtained by the hydration of benzyl groups of the polymer. Therefore, it is important to determine the to consider the difference in the reactivity in solution and in the solid state.
2. Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The oxazolidine ring (O2/N1/C1–C3) is planar with an r.m.s. deviation of 0.039 Å, and a maximum deviation of 0.033 (2) Å for atom C3. The side chain has an extended conformation with the C3—C4—C5—C6 and C7—C8—O4—C11 torsion angles being 98.8 (2) and 179.01 (18)°, respectively. Hence, the benzyloxy (C12–C17) and benzyl (C5–C10) rings are almost coplanar, making a dihedral angle of 0.078 (10)°, and are inclined to the oxazolidine ring by 59.16 (11) and 58.42 (11)°, respectively.
3. Supramolecular features
In the crystal, molecules are linked via N1—H1⋯O3i and C—H⋯O3ii hydrogen bonds, forming ribbons propagating along the b-axis direction (Table 1 and Fig. 2). The ribbons are linked by C—H⋯π interactions, forming a three-dimensional supramolecular structure (Table 1 and Fig. 3). The five-membered oxazolidine rings are packed in a layer and the –CH2C6H4OCH2C6H5 side chains are packed in another layer; the two different layers stack alternately. This sandwich structure is one of the important requirements for high reactivity in the solid state, because the five-membered rings can react with each other in the layer.
4. Database survey
A search of the Cambridge Structural Database (Version 5.37, update May 2016; Groom et al., 2016) revealed the presence of 15 hits for 4-methylene-oxazolidine-2,5-dione or 4-ethyl-4-methylene-oxazolidine-2,5-dione derivatives. A number of these compounds involve amino acid side chains (amino acid NCAs). There are four compounds in which a benzyl group side chain is bonded to atom C4 in the oxazolidine-2,5-dione ring, viz N-carboxy-L-phenylalanine anhydride (KIXSUF; Kanazawa, 2000), N-carboxy-DL-phenylalanine anhydride (RESSUD; Kanazawa et al., 1997), N-carboxy-(R)-phenylalanine anhydride 3-(2-thienyl) alanine-N-carboxyanhydride (SAPYEO; Nery et al.,2005) and Cα-ethyl-(S)-phenylalanine-N-carboxyanhydride (ZATWEW; Crisma et al.,1995). In these compounds, the dihedral angles between oxazolidine-2,5-dione ring mean plane and the benzene ring are very similar, viz 58.42 (11)° in the title compound, 59.34 (15)° in KIXSUF, 55.8 (2) and 54.7 (2)° in RESSUD, 51.7 (7), 50.6 (7)° in SAPYEO and 58.8 (7)° in ZATWEW. Intermolecular hydrogen bonds are formed between the imino group and the carbonyl O atom in position 2 of the oxazolidine ring in the title compound and in ZATWEW. On the other hand, they are formed between the imino group and the carbonyl O atom at position 5 of the oxazolidine ring in KIXSUF and RESSUD.
5. Synthesis and crystallization
Reagent-grade O-benzyl-L-tyrosine (OBLT) (Product Code B3210; Tokyo Kasei Co. Ltd.) was used as received. The title compound was synthesized by the reaction of OBLT with triphosgene in tetrahydrofuran, as reported previously for the synthesis of BLA NCA (Kanazawa & Magoshi, 2003). The reaction product was recrystallized slowly in a mixture of ethyl acetate and hexane (1:50 v/v), avoiding moisture contamination, and gave colourless needle-shaped crystals.
6. Refinement
Crystal data, data collection and structure . The N-bound H atom was located in a difference-Fourier map and refined with a distance restraint of N—H = 0.88 (4) Å, with Uiso(H) = 1.14Ueq(N). C-bound H atoms were positioned geometrically and treated as riding: C—H = 0.95–1.00 Å with Uiso(H) = 1.2Ueq(C).
details are summarized in Table 2Supporting information
CCDC reference: 1538344
https://doi.org/10.1107/S2056989017004236/su5359sup1.cif
contains datablocks I, Global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017004236/su5359Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017004236/su5359Isup3.cml
Data collection: RAPID-AUTO (Rigaku, 2009); cell
RAPID-AUTO (Rigaku, 2009); data reduction: RAPID-AUTO (Rigaku, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: CrystalStructure (Rigaku, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: CrystalStructure (Rigaku, 2009).C17H15NO4 | F(000) = 312 |
Mr = 297.30 | Dx = 1.376 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71075 Å |
Hall symbol: P 2yb | Cell parameters from 7077 reflections |
a = 7.7388 (5) Å | θ = 3.5–27.4° |
b = 5.9128 (4) Å | µ = 0.10 mm−1 |
c = 15.7769 (10) Å | T = 123 K |
β = 96.390 (2)° | Needle, colourless |
V = 717.43 (8) Å3 | 0.26 × 0.13 × 0.10 mm |
Z = 2 |
Rigaku R-AXIS RAPID diffractometer | 1635 independent reflections |
Radiation source: fine-focus sealed tube | 1444 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
Detector resolution: 10.0 pixels mm-1 | θmax = 26.5°, θmin = 3.5° |
ω–scan | h = −9→9 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −7→7 |
Tmin = 0.975, Tmax = 0.990 | l = −19→19 |
6593 measured 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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.068 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0302P)2 + 0.1082P] where P = (Fo2 + 2Fc2)/3 |
1635 reflections | (Δ/σ)max < 0.001 |
202 parameters | Δρmax = 0.20 e Å−3 |
1 restraint | Δρmin = −0.18 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. Refinement of F2 against ALL 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 > 2sigma(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 | 1.08406 (18) | 0.6360 (3) | 0.91435 (9) | 0.0310 (4) | |
O2 | 0.89115 (18) | 0.3443 (3) | 0.91282 (8) | 0.0238 (3) | |
O3 | 0.6500 (2) | 0.1393 (3) | 0.92135 (9) | 0.0290 (4) | |
O4 | 0.70846 (18) | 0.5324 (3) | 0.52871 (9) | 0.0265 (4) | |
N1 | 0.7966 (2) | 0.6908 (3) | 0.93804 (11) | 0.0229 (4) | |
H1 | 0.792 (3) | 0.840 (6) | 0.9383 (16) | 0.026* | |
C1 | 0.9379 (3) | 0.5765 (4) | 0.92122 (12) | 0.0234 (5) | |
C2 | 0.7201 (3) | 0.3211 (4) | 0.92381 (12) | 0.0221 (5) | |
C3 | 0.6426 (3) | 0.5499 (4) | 0.93569 (13) | 0.0213 (4) | |
H3 | 0.5941 | 0.5568 | 0.9918 | 0.026* | |
C4 | 0.4993 (2) | 0.6067 (4) | 0.86274 (12) | 0.0222 (5) | |
H4A | 0.4003 | 0.5022 | 0.8659 | 0.027* | |
H4B | 0.4570 | 0.7622 | 0.8712 | 0.027* | |
C5 | 0.5591 (2) | 0.5901 (4) | 0.77459 (12) | 0.0212 (5) | |
C6 | 0.5233 (3) | 0.3969 (4) | 0.72446 (13) | 0.0227 (5) | |
H6 | 0.4620 | 0.2743 | 0.7461 | 0.027* | |
C7 | 0.5764 (3) | 0.3826 (4) | 0.64309 (13) | 0.0229 (5) | |
H7 | 0.5524 | 0.2500 | 0.6098 | 0.027* | |
C8 | 0.6648 (2) | 0.5620 (4) | 0.61046 (13) | 0.0218 (4) | |
C9 | 0.7028 (3) | 0.7545 (4) | 0.65934 (13) | 0.0230 (5) | |
H9 | 0.7644 | 0.8766 | 0.6376 | 0.028* | |
C10 | 0.6491 (3) | 0.7661 (4) | 0.74112 (13) | 0.0233 (5) | |
H10 | 0.6750 | 0.8978 | 0.7746 | 0.028* | |
C11 | 0.7964 (3) | 0.7139 (4) | 0.49268 (12) | 0.0236 (5) | |
H11A | 0.9058 | 0.7481 | 0.5292 | 0.028* | |
H11B | 0.7226 | 0.8510 | 0.4896 | 0.028* | |
C12 | 0.8365 (2) | 0.6502 (4) | 0.40454 (13) | 0.0215 (4) | |
C13 | 0.7879 (3) | 0.4450 (4) | 0.36549 (13) | 0.0231 (5) | |
H13 | 0.7276 | 0.3355 | 0.3950 | 0.028* | |
C14 | 0.8277 (3) | 0.4004 (4) | 0.28317 (13) | 0.0245 (5) | |
H14 | 0.7950 | 0.2597 | 0.2571 | 0.029* | |
C15 | 0.9141 (3) | 0.5582 (4) | 0.23910 (13) | 0.0281 (5) | |
H15 | 0.9394 | 0.5271 | 0.1827 | 0.034* | |
C16 | 0.9636 (3) | 0.7619 (4) | 0.27748 (14) | 0.0293 (5) | |
H16 | 1.0239 | 0.8706 | 0.2476 | 0.035* | |
C17 | 0.9253 (3) | 0.8080 (4) | 0.35980 (13) | 0.0265 (5) | |
H17 | 0.9598 | 0.9482 | 0.3858 | 0.032* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0254 (8) | 0.0395 (10) | 0.0284 (7) | −0.0028 (8) | 0.0048 (6) | 0.0012 (7) |
O2 | 0.0264 (7) | 0.0216 (8) | 0.0242 (7) | 0.0054 (7) | 0.0067 (6) | 0.0018 (7) |
O3 | 0.0374 (9) | 0.0201 (8) | 0.0295 (8) | −0.0022 (7) | 0.0040 (7) | 0.0011 (7) |
O4 | 0.0333 (8) | 0.0254 (9) | 0.0214 (7) | −0.0067 (7) | 0.0060 (6) | −0.0013 (6) |
N1 | 0.0234 (9) | 0.0190 (10) | 0.0264 (8) | 0.0002 (8) | 0.0030 (7) | −0.0026 (8) |
C1 | 0.0263 (11) | 0.0272 (12) | 0.0164 (9) | 0.0002 (10) | 0.0020 (8) | 0.0030 (9) |
C2 | 0.0287 (11) | 0.0244 (12) | 0.0138 (9) | 0.0034 (10) | 0.0051 (8) | 0.0031 (8) |
C3 | 0.0249 (10) | 0.0194 (11) | 0.0208 (9) | −0.0005 (9) | 0.0084 (8) | −0.0008 (9) |
C4 | 0.0198 (9) | 0.0218 (12) | 0.0254 (10) | 0.0014 (9) | 0.0044 (8) | −0.0006 (9) |
C5 | 0.0156 (9) | 0.0241 (13) | 0.0232 (9) | 0.0043 (9) | −0.0002 (8) | 0.0016 (9) |
C6 | 0.0189 (10) | 0.0225 (12) | 0.0264 (10) | −0.0013 (9) | 0.0008 (8) | 0.0031 (9) |
C7 | 0.0209 (10) | 0.0209 (12) | 0.0258 (10) | −0.0011 (9) | −0.0024 (8) | −0.0025 (9) |
C8 | 0.0204 (10) | 0.0243 (11) | 0.0203 (9) | 0.0012 (10) | 0.0012 (8) | 0.0001 (9) |
C9 | 0.0243 (10) | 0.0212 (11) | 0.0232 (10) | −0.0020 (9) | 0.0012 (8) | 0.0033 (9) |
C10 | 0.0243 (11) | 0.0207 (12) | 0.0242 (10) | 0.0004 (9) | −0.0009 (8) | −0.0004 (9) |
C11 | 0.0250 (10) | 0.0223 (12) | 0.0234 (10) | −0.0022 (9) | 0.0020 (8) | 0.0017 (9) |
C12 | 0.0172 (9) | 0.0249 (11) | 0.0217 (9) | 0.0013 (9) | −0.0006 (8) | 0.0028 (9) |
C13 | 0.0212 (11) | 0.0216 (11) | 0.0265 (10) | 0.0009 (9) | 0.0021 (8) | 0.0028 (9) |
C14 | 0.0223 (11) | 0.0228 (12) | 0.0277 (10) | 0.0006 (9) | 0.0001 (9) | −0.0018 (9) |
C15 | 0.0263 (11) | 0.0344 (13) | 0.0241 (10) | 0.0029 (11) | 0.0045 (8) | −0.0038 (10) |
C16 | 0.0332 (12) | 0.0275 (13) | 0.0287 (11) | −0.0040 (10) | 0.0105 (9) | 0.0038 (10) |
C17 | 0.0264 (11) | 0.0240 (13) | 0.0290 (11) | −0.0039 (10) | 0.0024 (9) | −0.0024 (10) |
O1—C1 | 1.201 (2) | C7—H7 | 0.9500 |
O2—C2 | 1.361 (2) | C8—C9 | 1.388 (3) |
O2—C1 | 1.422 (3) | C9—C10 | 1.400 (3) |
O3—C2 | 1.202 (3) | C9—H9 | 0.9500 |
O4—C8 | 1.380 (2) | C10—H10 | 0.9500 |
O4—C11 | 1.423 (3) | C11—C12 | 1.506 (3) |
N1—C1 | 1.337 (3) | C11—H11A | 0.9900 |
N1—C3 | 1.451 (3) | C11—H11B | 0.9900 |
N1—H1 | 0.88 (3) | C12—C13 | 1.393 (3) |
C2—C3 | 1.500 (3) | C12—C17 | 1.396 (3) |
C3—C4 | 1.544 (3) | C13—C14 | 1.393 (3) |
C3—H3 | 1.0000 | C13—H13 | 0.9500 |
C4—C5 | 1.517 (3) | C14—C15 | 1.380 (3) |
C4—H4A | 0.9900 | C14—H14 | 0.9500 |
C4—H4B | 0.9900 | C15—C16 | 1.383 (3) |
C5—C10 | 1.389 (3) | C15—H15 | 0.9500 |
C5—C6 | 1.399 (3) | C16—C17 | 1.391 (3) |
C6—C7 | 1.394 (3) | C16—H16 | 0.9500 |
C6—H6 | 0.9500 | C17—H17 | 0.9500 |
C7—C8 | 1.391 (3) | ||
C2—O2—C1 | 109.05 (16) | O4—C8—C7 | 115.5 (2) |
C8—O4—C11 | 117.10 (17) | C9—C8—C7 | 120.15 (18) |
C1—N1—C3 | 113.10 (19) | C8—C9—C10 | 119.05 (19) |
C1—N1—H1 | 122.7 (16) | C8—C9—H9 | 120.5 |
C3—N1—H1 | 122.7 (16) | C10—C9—H9 | 120.5 |
O1—C1—N1 | 132.0 (2) | C5—C10—C9 | 121.8 (2) |
O1—C1—O2 | 120.44 (19) | C5—C10—H10 | 119.1 |
N1—C1—O2 | 107.53 (17) | C9—C10—H10 | 119.1 |
O3—C2—O2 | 121.8 (2) | O4—C11—C12 | 109.70 (18) |
O3—C2—C3 | 128.69 (18) | O4—C11—H11A | 109.7 |
O2—C2—C3 | 109.44 (18) | C12—C11—H11A | 109.7 |
N1—C3—C2 | 100.53 (16) | O4—C11—H11B | 109.7 |
N1—C3—C4 | 114.45 (17) | C12—C11—H11B | 109.7 |
C2—C3—C4 | 111.52 (18) | H11A—C11—H11B | 108.2 |
N1—C3—H3 | 110.0 | C13—C12—C17 | 118.84 (18) |
C2—C3—H3 | 110.0 | C13—C12—C11 | 123.57 (19) |
C4—C3—H3 | 110.0 | C17—C12—C11 | 117.6 (2) |
C5—C4—C3 | 113.72 (15) | C14—C13—C12 | 120.03 (19) |
C5—C4—H4A | 108.8 | C14—C13—H13 | 120.0 |
C3—C4—H4A | 108.8 | C12—C13—H13 | 120.0 |
C5—C4—H4B | 108.8 | C15—C14—C13 | 120.8 (2) |
C3—C4—H4B | 108.8 | C15—C14—H14 | 119.6 |
H4A—C4—H4B | 107.7 | C13—C14—H14 | 119.6 |
C10—C5—C6 | 118.23 (17) | C14—C15—C16 | 119.63 (19) |
C10—C5—C4 | 121.1 (2) | C14—C15—H15 | 120.2 |
C6—C5—C4 | 120.62 (18) | C16—C15—H15 | 120.2 |
C7—C6—C5 | 120.66 (19) | C15—C16—C17 | 120.2 (2) |
C7—C6—H6 | 119.7 | C15—C16—H16 | 119.9 |
C5—C6—H6 | 119.7 | C17—C16—H16 | 119.9 |
C8—C7—C6 | 120.1 (2) | C16—C17—C12 | 120.6 (2) |
C8—C7—H7 | 119.9 | C16—C17—H17 | 119.7 |
C6—C7—H7 | 119.9 | C12—C17—H17 | 119.7 |
O4—C8—C9 | 124.34 (19) | ||
C3—N1—C1—O1 | 176.8 (2) | C11—O4—C8—C7 | 179.01 (18) |
C3—N1—C1—O2 | −4.5 (2) | C6—C7—C8—O4 | −178.74 (18) |
C2—O2—C1—O1 | 179.56 (17) | C6—C7—C8—C9 | 1.1 (3) |
C2—O2—C1—N1 | 0.7 (2) | O4—C8—C9—C10 | 178.99 (19) |
C1—O2—C2—O3 | −178.53 (18) | C7—C8—C9—C10 | −0.8 (3) |
C1—O2—C2—C3 | 3.2 (2) | C6—C5—C10—C9 | 0.4 (3) |
C1—N1—C3—C2 | 6.0 (2) | C4—C5—C10—C9 | −179.00 (19) |
C1—N1—C3—C4 | −113.59 (19) | C8—C9—C10—C5 | 0.1 (3) |
O3—C2—C3—N1 | 176.5 (2) | C8—O4—C11—C12 | 178.88 (17) |
O2—C2—C3—N1 | −5.4 (2) | O4—C11—C12—C13 | 1.7 (3) |
O3—C2—C3—C4 | −61.8 (3) | O4—C11—C12—C17 | −179.17 (18) |
O2—C2—C3—C4 | 116.34 (17) | C17—C12—C13—C14 | −0.1 (3) |
N1—C3—C4—C5 | 58.2 (2) | C11—C12—C13—C14 | 179.01 (19) |
C2—C3—C4—C5 | −55.1 (2) | C12—C13—C14—C15 | −0.5 (3) |
C3—C4—C5—C10 | −81.9 (2) | C13—C14—C15—C16 | 0.8 (3) |
C3—C4—C5—C6 | 98.8 (2) | C14—C15—C16—C17 | −0.5 (3) |
C10—C5—C6—C7 | −0.1 (3) | C15—C16—C17—C12 | −0.1 (3) |
C4—C5—C6—C7 | 179.27 (18) | C13—C12—C17—C16 | 0.4 (3) |
C5—C6—C7—C8 | −0.6 (3) | C11—C12—C17—C16 | −178.8 (2) |
C11—O4—C8—C9 | −0.8 (3) |
Cg is the centroid of the C12–C17 benzyloxy ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O3i | 0.88 (3) | 2.09 (3) | 2.885 (2) | 150 (2) |
C3—H3···O3ii | 1.00 | 2.50 | 3.410 (3) | 151 |
C6—H6···Cgiii | 0.95 | 2.89 | 3.546 (3) | 127 |
Symmetry codes: (i) x, y+1, z; (ii) −x+1, y+1/2, −z+2; (iii) −x+1, y−1/2, −z+1. |
Acknowledgements
HK thanks the Rigaku Corporation, Tokyo, Japan, for assistance with the data collection of the title compound and Dr Hidehiro Uekusa of Tokyo Institute of Technology for assistance with the checking of the crystal-structure analysis of the title compound.
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