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Acta Crystallogr Sect E Struct Rep Online. 2010 April 1; 66(Pt 4): o724–o725.
Published online 2010 March 3. doi:  10.1107/S1600536810007397
PMCID: PMC2983926

4-[(2,4-Dimethyl-1,3-oxazol-5-yl)meth­yl]-4-hydr­oxy-2-methyl­isoquinoline-1,3(2H,4H)-dione

Abstract

In the title isoquinolinedione derivative, C16H16N2O4, the piperidine ring in the tetra­hydro­isoquinoline unit adopts a half-boat conformation. The essentially planar oxazole ring [maximum deviation = 0.004 (2) Å] is inclined at a dihedral angle of 36.00 (8)° to the tetra­hydro­isoquinoline unit. In the crystal structure, pairs of inter­molecular C—H(...)O and O—H(...)N inter­actions link the mol­ecules into chains incorporating R 2 2(9) ring motifs. Two neighbouring chains are further inter­connected by inter­molecular C—H(...)O inter­actions into chains two mol­ecules wide along the a axis.

Related literature

For general background to and applications of the title isoquinoline compound, see: Chen et al. (2006 [triangle]); Hall et al. (1994 [triangle]); Malamas & Hohman (1994 [triangle]); Mitchell et al. (1995 [triangle], 2000 [triangle]). For ring conformations, see: Cremer & Pople (1975 [triangle]). For hydrogen-bond motifs, see: Bernstein et al. (1995 [triangle]). For related structures, see: Subbiah Pandi et al. (2002 [triangle]); Wang et al. (2000 [triangle]). For bond-length data, see: Allen et al. (1987 [triangle]). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0o724-scheme1.jpg

Experimental

Crystal data

  • C16H16N2O4
  • M r = 300.31
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o724-efi1.jpg
  • a = 8.3866 (5) Å
  • b = 8.8044 (5) Å
  • c = 10.6734 (7) Å
  • α = 103.997 (3)°
  • β = 90.025 (3)°
  • γ = 112.663 (2)°
  • V = 701.80 (7) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.10 mm−1
  • T = 100 K
  • 0.24 × 0.19 × 0.08 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2009 [triangle]) T min = 0.976, T max = 0.992
  • 6623 measured reflections
  • 3198 independent reflections
  • 2401 reflections with I > 2σ(I)
  • R int = 0.034

Refinement

  • R[F 2 > 2σ(F 2)] = 0.050
  • wR(F 2) = 0.135
  • S = 1.04
  • 3198 reflections
  • 263 parameters
  • All H-atom parameters refined
  • Δρmax = 0.40 e Å−3
  • Δρmin = −0.28 e Å−3

Data collection: APEX2 (Bruker, 2009 [triangle]); cell refinement: SAINT (Bruker, 2009 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810007397/sj2737sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810007397/sj2737Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

Financial support from the Ministry of Science and Technology of China of the Austria–China Cooperation project (2007DFA41590) is acknowledged. HKF and JHG thank Universiti Sains Malaysia (USM) for the Research University Golden Goose grant (No. 1001/PFIZIK/811012). JHG also thanks USM for the award of a USM fellowship.

supplementary crystallographic information

Comment

A series of isoquinoline-1,3,4-trione derivatives were identified as novel and potent inhibitors of caspase-3 through structural modification of the original compounds from high-throughput screening (Chen et al., 2006). Moreover, the series of isoquinoline-1,3,4-triones were found to be fast-acting post-emergence herbicides, producing symptoms of desiccation (Mitchell et al., 2000). These redox-active compounds are very potent stimulators of the light-dependent consumption of oxygen at photosystem in isolated chloroplasts (Mitchell et al., 1995). Isoquinoline-1,3,4-trione derivatives have a variety of biological activities and are synthetic precursors for many naturally occuring alkaloids (Hall et al., 1994; Malamas & Hohman, 1994). The crystal structure of the related Z-2-methyl-3'-phenyl-spiro[isoquinoline-4,2'-oxirane]-1,3-dione has been reported (Wang et al., 2000).

In the title isoquinoline-1,3-dione compound (Fig. 1), the piperidine ring (C1/N1/C2/C3/C8/C9) in the 1,2,3,4-tetrahydroisoquinolin moiety adopts a half-boat conformation (Cremer & Pople, 1975) with puckering parameters of Q = 0.3114 (19) Å, θ = 71.4 (3)° and [var phi] = 114.9 (4)°. The oxazole ring (C11/C12/N2/C13/O4) is essentially planar with maximum deviation of -0.004 (2) Å at atom C13. The oxazole ring is inclined at a dihedral angle of 36.00 (8)° with the mean plane through 1,2,3,4-tetrahydroisoquinolin moiety. Bond lengths (Allen et al., 1987) and angles are normal and comparable to those related isoquinoline-1,3-dione structures (Wang et al., 2000; Subbiah Pandi et al., 2002).

In the crystal structure (Fig. 2), intermolecular O3—H1O3···N2 and C16—H16A···O1 hydrogen bonds (Table 1) link the molecules into one-dimensional chains along a axis incorporating R22(9) ring motifs (Bernstein et al., 1995). Two neighbouring chains are further interconnected by intermolecular C16—H16B···O1 hydrogen bonds into two-molecule-wide chains along the same axis.

Experimental

The title compound was obtained in the reaction between 1,3,4(2H)-isoquinolinetrione and 2,4,5-trimethyloxazole. The compound was purified by flash column chromatography in ethyl acetate and petroleum ether. X-ray quality single crystals of the title compound were obtained from slow evaporation of a chloroform solution. M.p. 434–436 K.

Refinement

All the H atoms were located from difference Fourier map [range of C—H = 0.91 (2) - 1.01 (3) Å] and allowed to refine freely.

Figures

Fig. 1.
The structure of the title compound, showing the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
Fig. 2.
The crystal structure of the title compound, showing two-molecule-wide chain along the a axis. H atoms not involved in intermolecular interactions (dashed lines) have been omitted for clarity.

Crystal data

C16H16N2O4Z = 2
Mr = 300.31F(000) = 316
Triclinic, P1Dx = 1.421 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 8.3866 (5) ÅCell parameters from 1833 reflections
b = 8.8044 (5) Åθ = 4.4–32.7°
c = 10.6734 (7) ŵ = 0.10 mm1
α = 103.997 (3)°T = 100 K
β = 90.025 (3)°Block, colourless
γ = 112.663 (2)°0.24 × 0.19 × 0.08 mm
V = 701.80 (7) Å3

Data collection

Bruker SMART APEXII CCD area-detector diffractometer3198 independent reflections
Radiation source: fine-focus sealed tube2401 reflections with I > 2σ(I)
graphiteRint = 0.034
[var phi] and ω scansθmax = 27.5°, θmin = 2.7°
Absorption correction: multi-scan (SADABS; Bruker, 2009)h = −10→10
Tmin = 0.976, Tmax = 0.992k = −11→11
6623 measured reflectionsl = −13→13

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.135All H-atom parameters refined
S = 1.04w = 1/[σ2(Fo2) + (0.0731P)2 + 0.0844P] where P = (Fo2 + 2Fc2)/3
3198 reflections(Δ/σ)max < 0.001
263 parametersΔρmax = 0.40 e Å3
0 restraintsΔρmin = −0.28 e Å3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
O11.23014 (16)0.40877 (16)0.32581 (13)0.0234 (3)
O20.76462 (17)0.27268 (17)0.04028 (14)0.0269 (3)
O31.13932 (17)0.07862 (17)0.33591 (13)0.0224 (3)
O40.78937 (15)0.36205 (15)0.40053 (12)0.0185 (3)
N10.99911 (18)0.34315 (18)0.18332 (15)0.0175 (3)
N20.50707 (18)0.22071 (19)0.33559 (15)0.0186 (3)
C11.0928 (2)0.3023 (2)0.26656 (17)0.0175 (4)
C20.8503 (2)0.2243 (2)0.10092 (18)0.0187 (4)
C30.8116 (2)0.0419 (2)0.08846 (17)0.0175 (4)
C40.6900 (2)−0.0817 (2)−0.01212 (19)0.0217 (4)
C50.6559 (2)−0.2517 (3)−0.0275 (2)0.0249 (4)
C60.7436 (3)−0.3003 (2)0.0555 (2)0.0249 (4)
C70.8637 (2)−0.1782 (2)0.15593 (19)0.0209 (4)
C80.8972 (2)−0.0063 (2)0.17380 (17)0.0171 (4)
C91.0118 (2)0.1260 (2)0.29105 (18)0.0175 (4)
C100.8979 (2)0.1419 (3)0.40732 (18)0.0191 (4)
C110.7513 (2)0.1891 (2)0.38373 (17)0.0172 (4)
C120.5796 (2)0.1033 (2)0.34423 (17)0.0180 (4)
C130.6360 (2)0.3692 (2)0.36869 (17)0.0179 (4)
C141.0594 (3)0.5246 (2)0.1865 (2)0.0238 (4)
C150.4717 (3)−0.0836 (2)0.3101 (2)0.0238 (4)
C160.6387 (2)0.5395 (2)0.3724 (2)0.0216 (4)
H1O31.243 (4)0.142 (3)0.321 (3)0.054 (8)*
H4A0.637 (3)−0.043 (3)−0.065 (2)0.033 (6)*
H5A0.574 (3)−0.336 (3)−0.097 (2)0.031 (6)*
H6A0.722 (3)−0.420 (3)0.045 (2)0.029 (6)*
H7A0.924 (3)−0.208 (2)0.217 (2)0.019 (5)*
H10A0.855 (3)0.032 (3)0.430 (2)0.024 (5)*
H10B0.979 (3)0.226 (3)0.484 (2)0.024 (5)*
H14A1.064 (3)0.595 (3)0.277 (3)0.045 (7)*
H14B0.985 (3)0.538 (3)0.127 (3)0.048 (7)*
H14C1.175 (4)0.565 (3)0.154 (3)0.052 (8)*
H15A0.436 (3)−0.124 (3)0.215 (3)0.037 (6)*
H15B0.530 (3)−0.148 (3)0.337 (2)0.040 (7)*
H15C0.360 (3)−0.114 (3)0.349 (3)0.047 (7)*
H16A0.526 (3)0.529 (3)0.344 (2)0.037 (6)*
H16B0.682 (3)0.622 (3)0.461 (3)0.039 (6)*
H16C0.718 (4)0.594 (3)0.314 (3)0.053 (8)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0134 (6)0.0238 (7)0.0300 (8)0.0053 (5)−0.0010 (5)0.0053 (6)
O20.0215 (7)0.0300 (8)0.0333 (8)0.0113 (6)−0.0025 (6)0.0136 (6)
O30.0105 (6)0.0283 (7)0.0340 (8)0.0096 (6)0.0033 (5)0.0151 (6)
O40.0104 (6)0.0223 (7)0.0219 (7)0.0072 (5)0.0009 (5)0.0026 (5)
N10.0133 (7)0.0185 (7)0.0224 (8)0.0073 (6)0.0023 (6)0.0070 (6)
N20.0116 (7)0.0221 (8)0.0226 (8)0.0077 (6)0.0020 (6)0.0052 (6)
C10.0132 (8)0.0217 (9)0.0203 (9)0.0095 (7)0.0049 (7)0.0063 (7)
C20.0126 (8)0.0260 (9)0.0204 (9)0.0092 (7)0.0053 (7)0.0088 (7)
C30.0113 (8)0.0210 (9)0.0203 (9)0.0062 (7)0.0045 (7)0.0057 (7)
C40.0157 (9)0.0290 (10)0.0205 (9)0.0086 (8)0.0036 (7)0.0073 (8)
C50.0167 (9)0.0267 (10)0.0240 (10)0.0045 (8)0.0035 (8)0.0004 (8)
C60.0225 (10)0.0201 (10)0.0315 (11)0.0087 (8)0.0095 (8)0.0055 (8)
C70.0167 (9)0.0220 (9)0.0271 (10)0.0098 (8)0.0055 (7)0.0086 (8)
C80.0115 (8)0.0212 (9)0.0203 (9)0.0075 (7)0.0058 (7)0.0070 (7)
C90.0112 (8)0.0249 (9)0.0210 (9)0.0102 (7)0.0026 (7)0.0090 (7)
C100.0122 (8)0.0270 (10)0.0199 (9)0.0086 (7)0.0022 (7)0.0079 (8)
C110.0133 (8)0.0224 (9)0.0162 (9)0.0075 (7)0.0033 (7)0.0047 (7)
C120.0143 (8)0.0236 (9)0.0174 (9)0.0087 (7)0.0025 (7)0.0055 (7)
C130.0108 (8)0.0256 (10)0.0169 (9)0.0080 (7)0.0009 (6)0.0036 (7)
C140.0230 (10)0.0190 (9)0.0302 (11)0.0084 (8)0.0015 (8)0.0077 (8)
C150.0157 (9)0.0219 (10)0.0333 (12)0.0055 (8)0.0027 (8)0.0099 (8)
C160.0139 (9)0.0216 (9)0.0285 (11)0.0067 (7)0.0011 (8)0.0059 (8)

Geometric parameters (Å, °)

O1—C11.219 (2)C6—H6A0.98 (2)
O2—C21.219 (2)C7—C81.392 (2)
O3—C91.4096 (19)C7—H7A0.97 (2)
O3—H1O30.87 (3)C8—C91.510 (2)
O4—C131.3590 (19)C9—C101.579 (3)
O4—C111.395 (2)C10—C111.481 (2)
N1—C11.381 (2)C10—H10A0.99 (2)
N1—C21.405 (2)C10—H10B1.00 (2)
N1—C141.469 (2)C11—C121.352 (2)
N2—C131.300 (2)C12—C151.491 (3)
N2—C121.407 (2)C13—C161.481 (3)
C1—C91.524 (2)C14—H14A1.01 (3)
C2—C31.482 (2)C14—H14B0.94 (3)
C3—C81.395 (2)C14—H14C0.99 (3)
C3—C41.398 (3)C15—H15A1.00 (3)
C4—C51.379 (3)C15—H15B0.97 (2)
C4—H4A0.91 (2)C15—H15C0.99 (3)
C5—C61.391 (3)C16—H16A0.95 (2)
C5—H5A0.96 (2)C16—H16B1.01 (3)
C6—C71.388 (3)C16—H16C0.98 (3)
C9—O3—H1O3111.7 (18)C1—C9—C10106.39 (14)
C13—O4—C11105.09 (13)C11—C10—C9115.98 (15)
C1—N1—C2124.28 (14)C11—C10—H10A110.1 (12)
C1—N1—C14116.33 (15)C9—C10—H10A106.9 (13)
C2—N1—C14119.36 (14)C11—C10—H10B111.0 (12)
C13—N2—C12105.17 (14)C9—C10—H10B106.8 (12)
O1—C1—N1120.67 (16)H10A—C10—H10B105.3 (17)
O1—C1—C9121.09 (15)C12—C11—O4107.30 (14)
N1—C1—C9118.01 (15)C12—C11—C10135.61 (17)
O2—C2—N1120.21 (16)O4—C11—C10117.05 (15)
O2—C2—C3123.36 (17)C11—C12—N2108.95 (15)
N1—C2—C3116.36 (14)C11—C12—C15129.76 (17)
C8—C3—C4120.28 (16)N2—C12—C15121.29 (15)
C8—C3—C2120.80 (16)N2—C13—O4113.49 (15)
C4—C3—C2118.91 (16)N2—C13—C16129.41 (16)
C5—C4—C3119.75 (18)O4—C13—C16117.08 (15)
C5—C4—H4A123.9 (14)N1—C14—H14A110.5 (14)
C3—C4—H4A116.4 (14)N1—C14—H14B109.2 (15)
C4—C5—C6120.24 (18)H14A—C14—H14B112 (2)
C4—C5—H5A119.7 (13)N1—C14—H14C110.9 (15)
C6—C5—H5A120.0 (13)H14A—C14—H14C110 (2)
C7—C6—C5120.25 (18)H14B—C14—H14C104 (2)
C7—C6—H6A118.6 (13)C12—C15—H15A108.7 (13)
C5—C6—H6A121.1 (13)C12—C15—H15B112.9 (14)
C6—C7—C8120.05 (18)H15A—C15—H15B111 (2)
C6—C7—H7A122.2 (12)C12—C15—H15C113.7 (15)
C8—C7—H7A117.7 (12)H15A—C15—H15C104 (2)
C7—C8—C3119.42 (17)H15B—C15—H15C106 (2)
C7—C8—C9120.71 (16)C13—C16—H16A110.0 (14)
C3—C8—C9119.63 (15)C13—C16—H16B112.3 (13)
O3—C9—C8112.25 (14)H16A—C16—H16B111 (2)
O3—C9—C1111.38 (14)C13—C16—H16C112.0 (16)
C8—C9—C1111.91 (14)H16A—C16—H16C106 (2)
O3—C9—C10105.32 (14)H16B—C16—H16C105 (2)
C8—C9—C10109.17 (14)
C2—N1—C1—O1172.69 (16)C3—C8—C9—C1−29.7 (2)
C14—N1—C1—O1−9.2 (3)C7—C8—C9—C10−86.56 (19)
C2—N1—C1—C9−12.7 (2)C3—C8—C9—C1087.76 (19)
C14—N1—C1—C9165.40 (16)O1—C1—C9—O3−27.0 (2)
C1—N1—C2—O2172.40 (17)N1—C1—C9—O3158.35 (15)
C14—N1—C2—O2−5.6 (3)O1—C1—C9—C8−153.60 (16)
C1—N1—C2—C3−10.5 (2)N1—C1—C9—C831.8 (2)
C14—N1—C2—C3171.54 (16)O1—C1—C9—C1087.24 (19)
O2—C2—C3—C8−170.30 (17)N1—C1—C9—C10−87.39 (18)
N1—C2—C3—C812.7 (2)O3—C9—C10—C11−179.26 (15)
O2—C2—C3—C411.0 (3)C8—C9—C10—C11−58.5 (2)
N1—C2—C3—C4−166.05 (16)C1—C9—C10—C1162.40 (19)
C8—C3—C4—C5−0.6 (3)C13—O4—C11—C12−0.42 (18)
C2—C3—C4—C5178.13 (17)C13—O4—C11—C10177.85 (15)
C3—C4—C5—C6−0.8 (3)C9—C10—C11—C1295.1 (3)
C4—C5—C6—C71.1 (3)C9—C10—C11—O4−82.6 (2)
C5—C6—C7—C8−0.1 (3)O4—C11—C12—N20.00 (19)
C6—C7—C8—C3−1.3 (3)C10—C11—C12—N2−177.81 (19)
C6—C7—C8—C9173.05 (17)O4—C11—C12—C15178.81 (18)
C4—C3—C8—C71.6 (3)C10—C11—C12—C151.0 (4)
C2—C3—C8—C7−177.07 (16)C13—N2—C12—C110.4 (2)
C4—C3—C8—C9−172.78 (16)C13—N2—C12—C15−178.48 (17)
C2—C3—C8—C98.5 (3)C12—N2—C13—O4−0.7 (2)
C7—C8—C9—O329.8 (2)C12—N2—C13—C16177.28 (19)
C3—C8—C9—O3−155.84 (15)C11—O4—C13—N20.75 (19)
C7—C8—C9—C1155.93 (16)C11—O4—C13—C16−177.54 (16)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O3—H1O3···N2i0.87 (3)2.04 (3)2.847 (2)153 (3)
C16—H16A···O1ii0.96 (3)2.28 (3)3.162 (2)153 (2)
C16—H16B···O1iii1.01 (3)2.50 (3)3.270 (2)132.9 (19)

Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) −x+2, −y+1, −z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2737).

References

  • Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.
  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Bruker (2009). APEX2, SAINT and SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Chen, Y.-H., Zhang, Y.-H., Zhang, H.-J., Liu, D.-Z., Gu, M., Li, J.-Y., Wu, F., Zhu, X.-Z., Li, J. & Nan, F.-J. (2006). J. Med. Chem.49, 1613–1623. [PubMed]
  • Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst.19, 105–107.
  • Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc.97, 1354–1358.
  • Hall, I. H., Chapman, J. M. & Wong, O. T. (1994). Anticancer Drugs, 5, 75–82. [PubMed]
  • Malamas, M. S. & Hohman, T. C. (1994). J. Med. Chem.37, 2043–2058. [PubMed]
  • Mitchell, G., Clarke, E. D., Ridley, S. M., Bartlett, D. W., Gillen, K. J., Vohra, S. K., Greenhow, D. T., Ormrod, J. C. & Wardman, P. (2000). Pest. Manag. Sci.56, 120–126.
  • Mitchell, G., Clarke, E. D., Ridley, S. M., Greenhow, D. T., Gillen, K. J., Vohra, S. K. & Wardman, P. (1995). Pestic. Sci.44, 49–58.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]
  • Subbiah Pandi, A., Rajakannan, V., Velmurugan, D., Parvez, M., Kim, M.-J., Senthilvelan, A. & Narasinga Rao, S. (2002). Acta Cryst. C58, o164–o167. [PubMed]
  • Wang, X.-L., Tian, J.-Z., Ling, K.-Q. & Xu, J.-H. (2000). Res. Chem. Intermed.26, 679–689.

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