(2S,3S)-2-(N,N-Dibenzyl­amino)­butane-1,3-diol refined using a multipolar atom model

The crystal structure of the title compound, C₁₈H₂₃NO₂, was determined using the experimental library multipolar atom model. The refinement showed a significant improvement of crystallographic statistical indices when compared with a conventional spherical neutral atom refinement.

S1. Comment

Enantiomerically pure amino acids and their derivatives play an important role as indispensable intermediates in the pharmaceutical industry and agrochemistry (Breuer et al., 2004, and references therein). Among these optically active amino-alcohols, L- and/or D-threoninol have received recently much attention as chiral parts of promising drugs against chemokine-mediated diseases (Brough & McInally, 2004), for the synthesis of acridine-DNA conjugates for site-selective RNA scissors (Shi et al., 2005), as linkers for methyl red incorporation into DNA (Kashida, Tanaka et al., 2006), as asymmetric cis-platinum(II) complexes for cancer therapy (van Rijt et al., 2006), as intercalator between pyrene moities and an oligodeoxyribonucleotide for the detection of deletion polymorphisms (Kashida, Asanuma et al., 2006) or between 10–23 DNAzyme and binding arm for RNA cleavage activity enhancement (Asanuma et al., 2006), and for the synthesis of inhibitors of protein kinase C for treatment of inflammation (Peng et al. 2006) or of a small combinatorial library of dihydroceramide analogs (Villorbina et al., 2007).

As part of a programme for the evaluation of new asymmetric catalysts from the chiral pool (Waykole et al., 2007) (ie. amino acids, sugars, etc), we have synthesized the new optically pure α-amino-alcohol (II) in two steps from readily available D-threonine. Diol (II) is a convenient source of D-threoninol by catalytic hydrogenolysis under mild conditions with toluene as sole by-product (Yoshida et al., 1988). We report here the X-ray structure of (II), which was prepared in good yield by reduction of the intermediate ester (I).

The molecular structure of (II) is depicted in Fig. 1. An intramolecular O1—HO1···N1 hydrogen bond (Table 2) forms five-membered ring. Atom N1 is about 0.407 Å out of the plane defined by three neighboring C atoms (C1, C5 and C12) towards hydrogen. The sum of valence angles around the N atom is 338.9°, indicating sp³-hybridization (328° for sp³ and 360° for sp²). The crystal structure of (II) is presented in Fig. 2. Chains along the b axis are formed by O2—HO2···O1ⁱ hydrogen bonds [symmetry code: (i) x, y + 1, z; Table 2].

Initially, in the independent atom model (IAM) refinement, a conventional spherical neutral atom model was applied. Scale factors, atomic positions and displacement parameters for all atoms were refined using the MoPro program (Guillot et al., 2001, Jelsch et al., 2005) until convergence. In the experimental library multipolar atom model (ELMAM) refinement, the same parameters were varied but a multipolar charged atom model was applied. The electron-density parameters were transferred from the ELMAM library (Pichon-Pesme et al., 2004; Zarychta et al., 2007) and subsequently kept fixed. Riding restraints on H-atom B factors were applied similarly in both refinements, which were carried out with the same intensity data and cut-off criterion [I/σ(I) ≥ 0]. The H—X distances were restricted to standard values in X-ray and neutron diffraction studies (Allen, 1986) in the IAM and ELMAM refinements, respectively (0.002 Å distance σ). The ELMAM refinement shows a good improvement in statistical indexes when compared with the IAM refinement; the R(F) factor is reduced from 4.22 to 3.02%, and wR(R) from 5.12 to 3.37%. The minimum and maximum peaks in the residual electron density are -0.036 and +0.056 e Å^-3 after the IAM refinement and -0.028 and +0.039 e Å^-3 after the ELMAN refinement. The most significant differences in the geometry of compound (II) are, as expected, the bond distances involving H atoms, which had different targets in the ELMAN and IAM refinements. When H atoms are not considered, the r.m.s. deviation between the two structures is 0.0067 Å, while the r.m.s. discrepancy for the bond lengths is 0.0055 Å. The differences do not exceed 0.015 Å for bond distances and 0.5° for bond angles when H atoms are excluded. The H—C—H angles show the strongest (2.9°) r.m.s. discrepancy, the X—Y—H angles differ by 1.8°, while the X—Y—Z angles are less affected with a low (0.2°) r.m.s. difference. The s.u. values of the bond distances and angles are smaller with the ELMAM owing to better R-factor values (Table 1).

The largest effect of the multipoles transfer on the crystallographic structure is observed in the atomic thermal motion. The r.m.s. difference over all the U_ij parameters reaches 16% between the two refinement models. The U_ij values derived from the IAM refinement have an r.m.s. value 10% larger on average than those derived from the ELMAM refinement. With the IAM spherical atom model, the displacement parameters are incorrect as they incorporate some significant deformation electron density, due to improper deconvolution between these two features (Jelsch et al., 1998).

Related literature

For related literature, see: Allen (1986); Asanuma et al. (2006); Breuer et al. (2004); Brough & McInally (2004); Flack (1983); Guillot et al. (2001); Jelsch et al. (1998, 2005); Kashida et al. (2006a, 2006b); Peng et al. (2006); Pichon-Pesme, Jelsch, Guillot & Lecomte (2004); Shi et al. (2005); Villorbina et al. (2007); Waykole et al. (2007); Yoshida et al. (1988); Zarychta et al. (2007).

S2. Experimental

For the preparation of (2R,3S)-2-N,N-dibenzylamino-3-hydroxybenzylbutanoate, (I), benzyl bromide (6.6 ml, 18.5 mmol, 3.3 equivalents) was dropped over a period of 30 min onto a magnetically stirred dispersion of 98% D-threonine (2.02 g, 16.6 mmol) and Na₂CO₃ (3.875 g, 19.5 mmol, ~2.2 equivalents) in 75% aqueous EtOH (50 ml) at room temperature. The resulting mixture was then refluxed for 2.5 h [the formation of (I) being monitored by SiO₂ thin-layer chromatography (TLC); Rf = 0.43; AcOEt–cyclohexane 1:4], cooled to room temperature, concentrated under reduced pressure, and partitioned between CH₂Cl₂ and water (2 × 50 ml). The aqueous phase was extracted with CH₂Cl₂ (3 × 50 ml). The combined organic phases were washed with saturated aqueous NaHCO₃ (50 ml) and water (3 × 50 ml), dried over MgSO₄, and finally concentrated in vacuo to afford the crude ester (I) as a pale-yellow syrup, which was used for the next step without further purification (yield 5.8 g, 14.9 mmol, ~90%). An analytical sample was isolated by TLC (SiO₂, AcOEt–hexane 1:9) as a colourless gum. [α]_D=+148.9° (c = 2.6, CHCl₃). MS (70 eV, EI⁺) calculated for C₂₅H₂₇NO₃ (389); found m/z (%) = 390 (23) [M+H]⁺, 344 (32) [M—C₂H₅O]⁺. IR (film): 1730 cm^-1; ¹H NMR (250 MHz, CDCl₃, 298 K, p.p.m): δ 7.15–7.55 (15H, m, aromatic), 5.35 (1H, d, J = 12.4 Hz, CHHPh), 5.22 (1H, d, CHHPh), 4.07 (1H, m, H-b), 4.07 (2H, d, J = 13.2 Hz, NCHHPh), 3.5 (1H, s, OH), 3.39 (2H, d, NCHHPh), 3.11 (1H, d, J = 9.5 Hz, H-α), 1.1 (3H, d, J = 5.8 Hz, CH₃). ¹³C NMR (100 MHz, CDCl₃, p.p.m.): δ 139.45 (C aromatic), 135.7 (C aromatic), 129.1, 128.7, 128.6, 128.5, 127.4 (CH aromatic), 67.2 (C-β), 66.3 (PhCH₂O), 63.2 (C-α), 54.8 (PhCH₂N), 19.2 (CH₃). Elemental analysis calculated for C₂₅H₂₇NO₃ (389.49): C 77.09, H 6.99, N 3.60%; found: C 76.91, H 6.81, N 3.67%.

For the preparation of (II), to a magnetically stirred suspension of 95% LiAlH₄ (0.78 g, ~19.5 mmol, 1.15 equivalents) in absolute THF (50 ml) under Ar cooled below 277 K was dropped a solution of crude ester (I) (5.453 g, 14.0 mmol) in absolute ether (50 ml) over a period of 30 min. The mixture was then stirred for 25 h at room temperature and refluxed for one additional hour. After completion of the reaction (checked by SiO₂ TLC; ethyl acetate–n-hexane 1:1; Rf ≈ 0.29), the mixture was cooled to room temperature, quenched by slow addition of ethyl acetate (5 ml) and saturated aqueous Na₂SO₄ (5 ml), and stirred overnight in air. The suspension was filtrated through a sintered glass and the remaining salts thoroughly washed with a CH₂Cl₂–ethanol mixture (1:1, 100 ml). The filtrates were concentrated under reduced pressure and the residue partioned in CH₂Cl₂ –water (2 × 50 ml), washed with water (2× 20 ml), dried over MgSO₄, concentrated under reduced pressure, and finally stored at 277 K. The resulting solids were isolated by filtration and crystallized twice from ethyl acetate–hexanes (1:19) to yield pure alcohol (II) (3.2 g, ~73%) as white crystals suitable for X-ray diffraction (m.p. 363–364 K; Tottoli). [α]_D=+54.0° (c = 1, CHCl₃). MS (70 eV, EI⁺): m/z 286.1 [M + H]^{+. 1}H NMR (250 MHz, CDCl₃/ε, D₂O, p.p.m.): δ 7.2–7.42 (m, 10H, aromatic), 3.99 (2H, d, J = 13.2 Hz, NCHHPh), 3.85 (1H, m, H-b), 3.8 (2H, d, J = 13.2 Hz, J = 5.8 Hz, CH₂OD), 3.72 (2H, d, NCHHPh), 2.61 (1H, d, J = 8.8 Hz, H-a), 1.15 (3H, d, J = 5.8 Hz, CH₃).¹³C NMR (100 MHz, CDCl₃, p.p.m.): δ 139.5 (C aromatic), 129.4, 128.7, 127.5 (CH aromatic), 65.5 (C-b), 64.8 (C-a); 59.1 (PhCH₂), 54.7 (CH₂—OH), 20.4 (CH₃). Elemental analysis calculated for C₁₈H₂₃NO₂ (285.39): C 75.76, H 8.12, N 4.91%; found: C 75.79, H 8.09, N 4.90%.

S3. Refinement

At first, a least-squares refinement, based on |F^{2|, was performed with program SHELXL-97(Sheldrick, 1997), the hydrogen atoms being constrained according to standard X-ray crystallography stereochemistry. Then a least-squares refinement, based on |F|, was carried out with the program MoPro (Guillot et al., 2001, Jelsch et al., 2005) using the ELMAM multipolar-atom model (Zarychta et al., 2007). The reflection weights were set equal to 1/σ}2^{(F_o). The U_iso(H) values were restrained to be 1.2U_eq of the attached atom with a standard deviation of 0.01 Å. In the absence of suitable anomalous scattering, the refinement of the Flack (1983) parameter led to inconclusive values; therefore Friedel equivalent reflections were merged prior to the final refinements. The absolute structure was set by reference to the known chirality of the enantiomeric pure D-Threonine used in the chemical synthesis.}

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1990); software used to prepare material for publication: publCIF (Westrip, 2007).

Figures

	Fig. 1. The molecular structure of (II) showing the hydrogen–bonding scheme (dashed lines). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The packing diagram of (II), showing arrangement of the chains.

(2S,3S)-2-(N,N-dibenzylamino)butane-1,3-diol

Crystal data

C18H23NO2	F(000) = 616
Mr = 285.37	Dx = 1.135 Mg m^−3
Monoclinic, C2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C 2y	Cell parameters from 3216 reflections
a = 18.6701 (4) Å	θ = 2.5–23.8°
b = 6.652 (1) Å	µ = 0.07 mm^−1
c = 16.060 (2) Å	T = 100 K
β = 123.126 (8)°	Prismatic, colourless
V = 1670.4 (3) Å^3	0.35 × 0.25 × 0.20 mm
Z = 4

Data collection

Radiation source: fine-focus sealed tube	Rint = 0.000
Graphite monochromator	θmax = 27.4°, θmin = 3.7°
2016 measured reflections	h = −23→20
2016 independent reflections	k = 0→8
1965 reflections with I > 2σ(I)	l = 0→20

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0542P)^2 + 0.793P] where P = (Fo^2 + 2Fc^2)/3
2016 reflections	(Δ/σ)max < 0.001
193 parameters	Δρmax = 0.28 e Å^−3
1 restraint	Δρmin = −0.16 e Å^−3

Special details

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 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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.25356 (8)	−0.1501 (2)	0.29809 (9)	0.0237 (3)
H1	0.2024	−0.1183	0.2564	0.036*
O2	0.23295 (8)	0.53289 (19)	0.39723 (10)	0.0236 (3)
H2	0.2437	0.6071	0.3631	0.035*
N1	0.15196 (8)	0.1614 (2)	0.28283 (10)	0.0160 (3)
C1	0.24683 (10)	0.1972 (3)	0.33879 (12)	0.0155 (3)
H1A	0.2608	0.2436	0.2900	0.019*
C2	0.29111 (10)	−0.0079 (3)	0.38078 (12)	0.0175 (3)
H2A	0.2784	−0.0548	0.4306	0.021*
C3	0.38880 (11)	−0.0072 (3)	0.43024 (13)	0.0252 (4)
H3A	0.4105	−0.1453	0.4469	0.038*
H3B	0.4157	0.0738	0.4910	0.038*
H3C	0.4024	0.0503	0.3842	0.038*
C4	0.28385 (10)	0.3538 (3)	0.42456 (12)	0.0190 (3)
H4A	0.2875	0.2919	0.4828	0.023*
H4B	0.3425	0.3903	0.4443	0.023*
C5	0.11876 (10)	0.1553 (3)	0.34968 (12)	0.0179 (3)
H5A	0.1074	0.2942	0.3616	0.021*
H5B	0.1631	0.0969	0.4146	0.021*
C6	0.03675 (10)	0.0312 (3)	0.30499 (12)	0.0185 (3)
C7	−0.03725 (11)	0.1123 (3)	0.29580 (12)	0.0211 (4)
H7	−0.0360	0.2460	0.3174	0.025*
C8	−0.11264 (11)	−0.0016 (3)	0.25519 (13)	0.0257 (4)
H8	−0.1617	0.0549	0.2498	0.031*
C9	−0.11528 (12)	−0.1978 (3)	0.22276 (13)	0.0246 (4)
H9	−0.1664	−0.2744	0.1939	0.030*
C10	−0.04146 (12)	−0.2811 (3)	0.23326 (14)	0.0249 (4)
H10	−0.0427	−0.4154	0.2124	0.030*
C11	0.03407 (11)	−0.1677 (3)	0.27433 (13)	0.0221 (4)
H11	0.0835	−0.2261	0.2814	0.026*
C12	0.09796 (10)	0.2986 (3)	0.19620 (12)	0.0183 (3)
H12A	0.1044	0.4377	0.2212	0.022*
H12B	0.0372	0.2599	0.1643	0.022*
C13	0.12040 (10)	0.2954 (3)	0.11695 (11)	0.0178 (3)
C14	0.11466 (11)	0.1178 (3)	0.06579 (13)	0.0224 (4)
H14	0.0976	−0.0038	0.0811	0.027*
C15	0.13415 (12)	0.1181 (3)	−0.00855 (14)	0.0283 (4)
H15	0.1301	−0.0032	−0.0421	0.034*
C16	0.15915 (12)	0.2953 (4)	−0.03249 (13)	0.0283 (4)
H16	0.1725	0.2951	−0.0817	0.034*
C17	0.16423 (12)	0.4724 (4)	0.01680 (13)	0.0280 (4)
H17	0.1805	0.5940	0.0005	0.034*
C18	0.14513 (11)	0.4725 (3)	0.09166 (13)	0.0224 (4)
H18	0.1492	0.5943	0.1249	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0249 (6)	0.0181 (6)	0.0245 (6)	0.0035 (5)	0.0111 (5)	−0.0015 (5)
O2	0.0276 (6)	0.0150 (6)	0.0285 (6)	0.0018 (5)	0.0156 (5)	−0.0004 (5)
N1	0.0139 (6)	0.0177 (7)	0.0163 (6)	0.0010 (5)	0.0081 (5)	0.0016 (5)
C1	0.0148 (7)	0.0148 (8)	0.0176 (7)	0.0009 (6)	0.0093 (6)	0.0010 (6)
C2	0.0192 (7)	0.0155 (8)	0.0186 (7)	0.0027 (7)	0.0109 (6)	0.0019 (7)
C3	0.0180 (8)	0.0253 (9)	0.0293 (9)	0.0053 (7)	0.0110 (7)	0.0049 (8)
C4	0.0184 (7)	0.0163 (8)	0.0203 (8)	−0.0005 (7)	0.0093 (6)	−0.0009 (7)
C5	0.0177 (7)	0.0199 (8)	0.0181 (7)	0.0001 (7)	0.0111 (6)	0.0000 (7)
C6	0.0186 (8)	0.0216 (8)	0.0168 (7)	0.0002 (7)	0.0105 (6)	0.0019 (7)
C7	0.0221 (8)	0.0224 (8)	0.0218 (8)	0.0021 (7)	0.0139 (7)	0.0016 (7)
C8	0.0194 (8)	0.0345 (10)	0.0268 (8)	0.0016 (8)	0.0149 (7)	0.0032 (8)
C9	0.0207 (8)	0.0315 (10)	0.0231 (8)	−0.0069 (8)	0.0128 (7)	0.0010 (8)
C10	0.0275 (9)	0.0214 (8)	0.0276 (9)	−0.0035 (8)	0.0163 (8)	−0.0005 (7)
C11	0.0198 (8)	0.0218 (9)	0.0264 (8)	0.0011 (7)	0.0137 (7)	0.0010 (7)
C12	0.0180 (7)	0.0184 (8)	0.0175 (7)	0.0036 (6)	0.0091 (6)	0.0022 (7)
C13	0.0142 (7)	0.0206 (8)	0.0148 (7)	0.0024 (6)	0.0056 (6)	0.0018 (7)
C14	0.0227 (8)	0.0202 (9)	0.0207 (8)	0.0006 (7)	0.0095 (7)	−0.0008 (7)
C15	0.0268 (9)	0.0340 (11)	0.0208 (8)	0.0054 (8)	0.0108 (7)	−0.0041 (8)
C16	0.0219 (8)	0.0441 (12)	0.0191 (8)	0.0048 (8)	0.0115 (7)	0.0028 (9)
C17	0.0236 (9)	0.0358 (11)	0.0229 (8)	−0.0032 (8)	0.0115 (7)	0.0056 (8)
C18	0.0229 (8)	0.0212 (9)	0.0205 (8)	−0.0003 (7)	0.0101 (7)	0.0001 (7)

Geometric parameters (Å, º)

O1—C2	1.460 (2)	C7—H7	0.9500
O1—H1	0.8400	C8—C9	1.396 (3)
O2—C4	1.435 (2)	C8—H8	0.9500
O2—H2	0.8400	C9—C10	1.407 (3)
N1—C12	1.500 (2)	C9—H9	0.9500
N1—C1	1.504 (2)	C10—C11	1.406 (3)
N1—C5	1.505 (2)	C10—H10	0.9500
C1—C2	1.546 (2)	C11—H11	0.9500
C1—C4	1.555 (2)	C12—C13	1.542 (2)
C1—H1A	1.0000	C12—H12A	0.9900
C2—C3	1.541 (2)	C12—H12B	0.9900
C2—H2A	1.0000	C13—C18	1.403 (3)
C3—H3A	0.9800	C13—C14	1.409 (2)
C3—H3B	0.9800	C14—C15	1.426 (3)
C3—H3C	0.9800	C14—H14	0.9500
C4—H4A	0.9900	C15—C16	1.397 (3)
C4—H4B	0.9900	C15—H15	0.9500
C5—C6	1.530 (2)	C16—C17	1.393 (3)
C5—H5A	0.9900	C16—H16	0.9500
C5—H5B	0.9900	C17—C18	1.429 (3)
C6—C11	1.403 (3)	C17—H17	0.9500
C6—C7	1.414 (2)	C18—H18	0.9500
C7—C8	1.406 (3)
C2—O1—H1	109.5	C8—C7—H7	119.5
C4—O2—H2	109.5	C6—C7—H7	119.5
C12—N1—C1	115.65 (13)	C9—C8—C7	119.96 (17)
C12—N1—C5	110.36 (12)	C9—C8—H8	120.0
C1—N1—C5	112.81 (12)	C7—C8—H8	120.0
N1—C1—C2	107.17 (13)	C8—C9—C10	119.39 (17)
N1—C1—C4	116.32 (13)	C8—C9—H9	120.3
C2—C1—C4	109.38 (13)	C10—C9—H9	120.3
N1—C1—H1A	107.9	C11—C10—C9	120.71 (18)
C2—C1—H1A	107.9	C11—C10—H10	119.6
C4—C1—H1A	107.9	C9—C10—H10	119.6
O1—C2—C3	108.40 (13)	C6—C11—C10	120.32 (17)
O1—C2—C1	107.36 (12)	C6—C11—H11	119.8
C3—C2—C1	114.97 (14)	C10—C11—H11	119.8
O1—C2—H2A	108.7	N1—C12—C13	114.15 (13)
C3—C2—H2A	108.7	N1—C12—H12A	108.7
C1—C2—H2A	108.7	C13—C12—H12A	108.7
C2—C3—H3A	109.5	N1—C12—H12B	108.7
C2—C3—H3B	109.5	C13—C12—H12B	108.7
H3A—C3—H3B	109.5	H12A—C12—H12B	107.6
C2—C3—H3C	109.5	C18—C13—C14	117.83 (14)
H3A—C3—H3C	109.5	C18—C13—C12	120.55 (15)
H3B—C3—H3C	109.5	C14—C13—C12	121.61 (16)
O2—C4—C1	112.68 (13)	C13—C14—C15	120.95 (18)
O2—C4—H4A	109.1	C13—C14—H14	119.5
C1—C4—H4A	109.1	C15—C14—H14	119.5
O2—C4—H4B	109.1	C16—C15—C14	120.55 (19)
C1—C4—H4B	109.1	C16—C15—H15	119.7
H4A—C4—H4B	107.8	C14—C15—H15	119.7
N1—C5—C6	112.13 (13)	C17—C16—C15	119.09 (16)
N1—C5—H5A	109.2	C17—C16—H16	120.5
C6—C5—H5A	109.2	C15—C16—H16	120.5
N1—C5—H5B	109.2	C16—C17—C18	120.51 (19)
C6—C5—H5B	109.2	C16—C17—H17	119.7
H5A—C5—H5B	107.9	C18—C17—H17	119.7
C11—C6—C7	118.55 (16)	C13—C18—C17	121.07 (18)
C11—C6—C5	120.54 (15)	C13—C18—H18	119.5
C7—C6—C5	120.90 (16)	C17—C18—H18	119.5
C8—C7—C6	121.06 (17)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—HO1···N1	0.97	2.06	2.729 (3)	125
O2—HO2···O1^i	0.97	1.87	2.789 (2)	158

Symmetry code: (i) x, y+1, z.