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The title compound, 11-chloro-8,12b-di­hydro-2,8-di­methyl-12b-phenyl-4H-[1,3]­oxazino­[3,2-d][1,4]­benzodiazepine-4,7(6H)-dione, C20H17ClN2O3, is a benzodiazepine with an additional d-face-fused heterocyclic ring. In the mol­ecule, a dihedral angle of 86.2 (1)° is formed by the planes of the phenyl and benzo rings and the former is axially oriented from the core, i.e. the fused 6,7,6-tricyclic system. Both heterocycles in the core suffer significant deviations from planarity. The central diazepine ring is a twist-boat and the oxazine ring exhibits a conformation intermediate between half-chair and sofa.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101006175/na1513sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101006175/na1513Isup2.hkl
Contains datablock I

CCDC reference: 169949

Comment top

Many benzodiazepines are used as pharmacotherapy of several neurologic and psychiatric disorders because of their efficacy in the treatment of conditions involving a dysfunction of the GABAergic transmission in the central nervous system (Bradwejn, 1993; Gracies et al., 1997; Mohler, 1998; Nelson & Chouinard, 1999). The title compound, Ketazolam, (I), which is a benzodiazepine of the type possessing an additional fused heterocyclic ring, has proven safe and effective antispastic action (Basmajian et al., 1984) as well as effectiveness in the treatment of a variety of manifestations of anxiety (Fabre & Harris, 1976; Fabre et al., 1981). \sch

The crystal structure has previously been studied, the cell parameters have been reported (Szmuszkovicz et al., 1971) and deposited without any structural information in the Cambridge Structural Database (refcode CHMPOA) [CSD; Allen et al., 1983]; besides, in the final publication the crystal structure is not actually described. Despite the fact that in the CSD there is available information of 5-phenyl-1,4-benzodiazepines attaching an additional O-containing ring, none of these has an oxazine ring.

This work is part of our ongoing study on benzodiazepines and derived compounds (Vega et al., 1999) and was undertaken to give a detailed description of intra- and intermolecular features of a member of this family of drugs.

In the asymmetric unit of the title compound, the C15—C16 bond makes an angle of 85.3 (4)° with the plane through the oxazine ring so, as is apparent in Fig. 1, the phenyl ring protrudes axially from the tricyclic core of the molecule due to the sp3 character and tetrahedral angle configuration of the C15 carbon (see Table 1). The phenyl ring could be oriented around the C15—C16 bond in such a way either as to avoid a steric hindrance between H18 and H13 at 1/2 - x, y - 1/2, -z - 1/2 (distance H18···H13 2.42 Å) or as to maximize hydrogen bond interactions involving C20—H20···O4i and C17—H17···N5. The value of the N5—C15—C16—C17 torsion angle [-0.8 (4)°] indicates that the C16—C17 bond of the phenyl ring is coplanar with the C15—N5 bond of the core.

A geometrical descriptor common to benzodiazepines has been the dihedral angle between the phenyl and the benzo rings, ranging from 54 to 75° for 5-(unsubstituted)phenyl-1,4-benzodiazepines (Chananont et al., 1980; Hamor & Martin, 1983; Butcher & Hamor, 1985). In this work, the phenyl ring sustains a dihedral angle of 86.2 (1)° with the benzo ring, which exceeds by more than 10° the value cited in the literature.

The six-membered rings of the core, the oxazine heterocycle and the benzo ring, are fused to the N5—C15 side (d-face) and across the C9—C14 bond of the central diazepine ring, respectively. The former has a conformation intermediate between half-chair and sofa [the ring puckering parameters (Cremer & Pople, 1975) for the sequence C3,C2,O1,C15,N5,C4 are QT 0.427 (3) Å, θ2 63.8 (4)° and ϕ2 165.4 (5)°, and the asymmetry parameters (Nardelli, 1983) are Δ2(C3—C4) 0.061 (1) and Δs(C3) 0.069 (1)] whereas the latter is slightly deviated from planarity [maximum deviation from least-squares plane defined by C9,C10,C11,C12,C13,C14 and Cl1 of 0.038 (4) Å at C11].

The diazepine ring adopts a twist-boat conformation, the ring puckering parameters for the sequence N5,C15,C14,C9,N8,C7,C6 are QT 1.066 (3) Å, θ2 82.4 (2)°, ϕ2 92.6 (2)° and ϕ3 97 (1)°. The asymmetry parameters are Δs(C6) 0.114 (1) and Δ2(N5) 0.028 (1), i.e. with a local pseudo-twofold axis running along N5 and the mid-point of the C9—N8 bond corresponding to a twisted conformation. The asymmetry parameter is representative of the degree of departure from a boat-like conformation of the diazepine ring. By comparison, the Δs(C6) averages 0.009 (2) [four independent molecules] for such a ring in the benzodiazepine Alprazolam (Vega et al., 1999), hence showing a pseudosymmetry mirror plane passing through the bow atom and the midpoint of the opposite bond, i.e. the diazepine ring has an almost perfect boat conformation.

The amide bonds in the vicinity of C6 atom, N8—C7 and N5—C4, are affected by electron delocalization between the nitrogen lone pair and the carbonyl oxygen. The bond has a length about halfway between the C—N pure single- and double-bond distances and the valency angles at the N atoms are close to 120° (see table 1). The overall geometry of the C—N bonds resembles that of a normal double bond and their planar nature are illustrated by the values of the torsion angles of the sequences C15—N5—C4—O4 and C9—N8—C7—O7 [171.1 (3) and -178.7 (3)°, respectively].

The packing for the crystal involves the use of both keto O atoms and the halogen atom as hydrogen-bond acceptor sites in very weak intermolecular hydrogen bondings, the donors being methyl and aryl carbons (see Table 2). The C—H···O contacts determine chains of molecules running along the crystallographic b direction; meanwhile, parallel chains are held together by the C—H···Cl hydrogen bonds thus forming a layer of molecules, and the packing of a crystal of Ketazolam comprises the stacking of layers.

Experimental top

The compound was obtained from LABORATORIOS GADOR. Crystals suitable for X-ray diffraction were obtained through slow evaporation from water solution.

Refinement top

The positional parameters of the H atoms were constrained to have C—H distances of 0.96 Å for primary, 0.97 Å for secondary, and 0.93 Å for aromatic H atoms. The H atoms were treated as riding and their isotropic thermal parameters were constrained to be 1.2 times larger than those of their hosts (1.5 for methyl groups). Data collection was performed at the Laboratorio Nacional de Difracción (LANADI).

Computing details top

Data collection: CAD-4-PC (Enraf Nonius, 1993); cell refinement: CAD-4-PC; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PARST (Nardelli, 1995), CSD (Allen et al., 1983) and WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. View of the structure showing the numbering scheme used and displacement ellipsoids drawn at 30% probability.
(I) top
Crystal data top
C20H17ClN2O3Dx = 1.403 Mg m3
Mr = 368.81Melting point: 455 K
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 8.6326 (9) ÅCell parameters from 25 reflections
b = 13.119 (1) Åθ = 10–20°
c = 15.505 (4) ŵ = 0.24 mm1
β = 96.19 (1)°T = 293 K
V = 1745.7 (5) Å3Prism, colourless
Z = 40.36 × 0.2 × 0.14 mm
F(000) = 768
Data collection top
CAD4
diffractometer
Rint = 0.031
ω–2θ scansθmax = 25°, θmin = 2.0°
Absorption correction: numerical
integration (Sheldrick, 1976)
h = 1010
Tmin = 0.91, Tmax = 0.94k = 115
3493 measured reflectionsl = 018
3071 independent reflections2 standard reflections every 98 reflections
1551 reflections with I > 2σ(I) intensity decay: <2%
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.046 w = 1/[σ2(Fo2) + (0.0369P)2 + 0.9696P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.132(Δ/σ)max < 0.001
S = 1.07Δρmax = 0.22 e Å3
3071 reflectionsΔρmin = 0.24 e Å3
235 parameters
Crystal data top
C20H17ClN2O3V = 1745.7 (5) Å3
Mr = 368.81Z = 4
Monoclinic, P21/nMo Kα radiation
a = 8.6326 (9) ŵ = 0.24 mm1
b = 13.119 (1) ÅT = 293 K
c = 15.505 (4) Å0.36 × 0.2 × 0.14 mm
β = 96.19 (1)°
Data collection top
CAD4
diffractometer
1551 reflections with I > 2σ(I)
Absorption correction: numerical
integration (Sheldrick, 1976)
Rint = 0.031
Tmin = 0.91, Tmax = 0.942 standard reflections every 98 reflections
3493 measured reflections intensity decay: <2%
3071 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0460 restraints
wR(F2) = 0.132H-atom parameters constrained
S = 1.07Δρmax = 0.22 e Å3
3071 reflectionsΔρmin = 0.24 e Å3
235 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.0413 (2)0.31121 (17)0.17074 (14)0.0406 (6)
O40.0803 (3)0.0213 (2)0.14088 (19)0.0619 (8)
O70.3936 (3)0.0127 (2)0.09127 (18)0.0631 (8)
N50.0977 (3)0.1480 (2)0.11214 (17)0.0392 (7)
N80.4486 (3)0.1530 (2)0.06120 (18)0.0443 (7)
C20.0752 (4)0.2699 (3)0.2273 (2)0.0430 (9)
C30.1081 (4)0.1718 (3)0.2243 (2)0.0461 (9)
H30.18260.14450.26570.055*
C40.0314 (4)0.1053 (3)0.1583 (2)0.0458 (9)
C60.1877 (4)0.0886 (3)0.0445 (2)0.0457 (9)
H6B0.13680.02360.03780.055*
H6A0.19170.12480.01030.055*
C70.3524 (4)0.0705 (3)0.0671 (2)0.0467 (9)
C80.6064 (4)0.1430 (4)0.0865 (3)0.0686 (13)
H8C0.62240.07440.10510.103*
H8B0.68080.15880.03780.103*
H8A0.61940.18920.13320.103*
C90.4007 (4)0.2487 (3)0.0313 (2)0.0403 (8)
C100.4911 (4)0.3002 (3)0.0345 (2)0.0514 (10)
H100.58540.27220.05780.062*
C110.4437 (4)0.3913 (3)0.0655 (2)0.0543 (11)
H110.50620.42580.10850.065*
C120.3031 (4)0.4311 (3)0.0324 (2)0.0473 (9)
C130.2120 (4)0.3836 (3)0.0330 (2)0.0407 (9)
H130.11690.41210.05440.049*
C140.2610 (4)0.2926 (2)0.0677 (2)0.0349 (8)
C150.1648 (3)0.2412 (3)0.1429 (2)0.0362 (8)
C160.2586 (3)0.2249 (3)0.2203 (2)0.0347 (8)
C170.2796 (4)0.1313 (3)0.2568 (2)0.0464 (9)
H170.23490.07370.23460.056*
C180.3667 (4)0.1218 (3)0.3261 (3)0.0620 (12)
H180.38210.05790.34970.074*
C190.4300 (5)0.2061 (4)0.3601 (3)0.0654 (12)
H190.4880.19960.4070.078*
C200.4083 (4)0.2997 (3)0.3255 (3)0.0617 (12)
H200.45090.35710.3490.074*
C210.3234 (4)0.3092 (3)0.2558 (2)0.0507 (10)
H210.30930.37340.23230.061*
C220.1521 (4)0.3485 (3)0.2865 (2)0.0597 (11)
H22C0.23390.31740.32440.09*
H22B0.07670.3780.32030.09*
H22A0.19510.40080.25290.09*
Cl10.23773 (14)0.54380 (9)0.07470 (7)0.0750 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0346 (12)0.0436 (14)0.0422 (13)0.0111 (11)0.0026 (11)0.0006 (11)
O40.0481 (16)0.0479 (17)0.089 (2)0.0120 (14)0.0039 (14)0.0032 (15)
O70.0612 (17)0.0491 (17)0.077 (2)0.0150 (14)0.0010 (14)0.0026 (15)
N50.0331 (15)0.0408 (17)0.0432 (17)0.0019 (14)0.0020 (13)0.0064 (14)
N80.0341 (16)0.0487 (19)0.0498 (18)0.0080 (15)0.0027 (13)0.0110 (15)
C20.0284 (18)0.066 (3)0.0343 (19)0.0053 (18)0.0037 (15)0.0013 (19)
C30.0331 (19)0.059 (3)0.046 (2)0.0071 (18)0.0007 (16)0.003 (2)
C40.035 (2)0.050 (2)0.053 (2)0.0003 (19)0.0092 (18)0.006 (2)
C60.045 (2)0.045 (2)0.047 (2)0.0006 (18)0.0029 (17)0.0128 (18)
C70.042 (2)0.049 (2)0.047 (2)0.008 (2)0.0024 (17)0.0123 (19)
C80.040 (2)0.080 (3)0.088 (3)0.015 (2)0.016 (2)0.009 (3)
C90.0327 (18)0.047 (2)0.0420 (19)0.0006 (17)0.0058 (16)0.0085 (17)
C100.039 (2)0.071 (3)0.042 (2)0.006 (2)0.0032 (17)0.008 (2)
C110.054 (2)0.068 (3)0.040 (2)0.018 (2)0.0019 (19)0.007 (2)
C120.053 (2)0.053 (2)0.038 (2)0.008 (2)0.0136 (18)0.0070 (18)
C130.0394 (19)0.046 (2)0.037 (2)0.0008 (17)0.0030 (16)0.0003 (17)
C140.0340 (17)0.039 (2)0.0316 (17)0.0023 (16)0.0036 (14)0.0045 (16)
C150.0289 (17)0.040 (2)0.0397 (18)0.0038 (16)0.0015 (15)0.0024 (17)
C160.0298 (17)0.0382 (19)0.0352 (18)0.0020 (16)0.0003 (15)0.0019 (16)
C170.046 (2)0.047 (2)0.047 (2)0.0007 (18)0.0064 (18)0.0071 (18)
C180.059 (3)0.066 (3)0.062 (3)0.002 (2)0.011 (2)0.024 (2)
C190.054 (3)0.093 (4)0.052 (3)0.003 (3)0.021 (2)0.011 (3)
C200.062 (3)0.065 (3)0.062 (3)0.009 (2)0.024 (2)0.004 (2)
C210.051 (2)0.049 (2)0.054 (2)0.0009 (19)0.0115 (19)0.002 (2)
C220.052 (2)0.074 (3)0.051 (2)0.013 (2)0.0054 (19)0.004 (2)
Cl10.0880 (8)0.0695 (7)0.0698 (7)0.0057 (6)0.0188 (6)0.0287 (6)
Geometric parameters (Å, º) top
O1—C21.372 (4)C9—C141.399 (4)
O1—C151.438 (4)C10—C111.367 (5)
O4—C41.221 (4)C11—C121.369 (5)
O7—C71.219 (4)C12—C131.364 (5)
N5—C41.377 (4)C12—Cl11.736 (4)
N5—C151.455 (4)C13—C141.395 (4)
N5—C61.462 (4)C14—C151.515 (4)
N8—C71.361 (4)C15—C161.534 (4)
N8—C91.416 (4)C16—C171.372 (5)
N8—C81.463 (4)C16—C211.381 (5)
C2—C31.320 (5)C17—C181.382 (5)
C2—C221.488 (5)C18—C191.365 (6)
C3—C41.449 (5)C19—C201.360 (5)
C6—C71.519 (5)C20—C211.375 (5)
C9—C101.390 (5)
C2—O1—C15114.1 (3)C10—C11—C12119.3 (4)
C4—N5—C15120.0 (3)C13—C12—C11121.4 (3)
C4—N5—C6119.7 (3)C13—C12—Cl1119.0 (3)
C15—N5—C6118.9 (3)C11—C12—Cl1119.7 (3)
C7—N8—C9122.0 (3)C12—C13—C14120.2 (3)
C7—N8—C8119.4 (3)C13—C14—C9118.7 (3)
C9—N8—C8118.7 (3)C13—C14—C15121.0 (3)
C3—C2—O1120.5 (3)C9—C14—C15120.3 (3)
C3—C2—C22127.9 (3)O1—C15—N5109.1 (2)
O1—C2—C22111.6 (3)O1—C15—C14105.9 (3)
C2—C3—C4121.9 (3)N5—C15—C14109.0 (3)
O4—C4—N5122.1 (4)O1—C15—C16107.0 (2)
O4—C4—C3123.8 (3)N5—C15—C16113.7 (3)
N5—C4—C3113.9 (3)C14—C15—C16111.8 (2)
N5—C6—C7110.9 (3)C17—C16—C21118.4 (3)
O7—C7—N8122.4 (3)C17—C16—C15123.5 (3)
O7—C7—C6121.5 (4)C21—C16—C15118.1 (3)
N8—C7—C6116.1 (3)C16—C17—C18120.5 (4)
C10—C9—C14119.2 (3)C19—C18—C17120.1 (4)
C10—C9—N8120.7 (3)C20—C19—C18120.1 (4)
C14—C9—N8120.1 (3)C19—C20—C21120.0 (4)
C11—C10—C9121.1 (4)C20—C21—C16120.9 (4)
C15—O1—C2—C329.4 (4)N8—C9—C14—C13175.8 (3)
C15—O1—C2—C22151.3 (3)C10—C9—C14—C15176.5 (3)
O1—C2—C3—C44.3 (5)N8—C9—C14—C153.7 (4)
C22—C2—C3—C4174.9 (3)C2—O1—C15—N550.8 (3)
C15—N5—C4—O4171.1 (3)C2—O1—C15—C14168.0 (2)
C6—N5—C4—O45.0 (5)C2—O1—C15—C1672.6 (3)
C15—N5—C4—C312.9 (4)C4—N5—C15—O143.7 (4)
C6—N5—C4—C3179.0 (3)C6—N5—C15—O1150.2 (3)
C2—C3—C4—O4163.1 (4)C4—N5—C15—C14158.9 (3)
C2—C3—C4—N512.8 (5)C6—N5—C15—C1435.0 (4)
C4—N5—C6—C7116.7 (3)C4—N5—C15—C1675.6 (3)
C15—N5—C6—C749.4 (4)C6—N5—C15—C1690.6 (3)
C9—N8—C7—O7178.7 (3)C13—C14—C15—O17.2 (4)
C8—N8—C7—O71.4 (5)C9—C14—C15—O1173.3 (3)
C9—N8—C7—C63.3 (5)C13—C14—C15—N5110.0 (3)
C8—N8—C7—C6176.7 (3)C9—C14—C15—N569.5 (4)
N5—C6—C7—O7106.0 (4)C13—C14—C15—C16123.4 (3)
N5—C6—C7—N872.0 (4)C9—C14—C15—C1657.1 (4)
C7—N8—C9—C10128.6 (4)O1—C15—C16—C17121.2 (3)
C8—N8—C9—C1051.5 (5)N5—C15—C16—C170.8 (4)
C7—N8—C9—C1451.2 (4)C14—C15—C16—C17123.2 (3)
C8—N8—C9—C14128.7 (3)O1—C15—C16—C2157.8 (4)
C14—C9—C10—C111.7 (5)N5—C15—C16—C21178.2 (3)
N8—C9—C10—C11178.1 (3)C14—C15—C16—C2157.8 (4)
C9—C10—C11—C121.5 (5)C21—C16—C17—C181.5 (5)
C10—C11—C12—C132.4 (5)C15—C16—C17—C18179.5 (3)
C10—C11—C12—Cl1177.1 (3)C16—C17—C18—C191.3 (6)
C11—C12—C13—C140.0 (5)C17—C18—C19—C200.4 (6)
Cl1—C12—C13—C14179.5 (2)C18—C19—C20—C210.4 (6)
C12—C13—C14—C93.2 (5)C19—C20—C21—C160.3 (6)
C12—C13—C14—C15177.3 (3)C17—C16—C21—C200.7 (5)
C10—C9—C14—C134.0 (5)C15—C16—C21—C20179.8 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C6—H6B···O40.972.332.760 (4)106
C8—H8C···O70.962.312.743 (5)106
C13—H13···O10.932.282.637 (4)102
C17—H17···N50.932.542.882 (4)102
C20—H20···O4i0.932.443.332 (5)161
C22—H22A···Cl1ii0.962.923.721 (4)142
C22—H22B···O7i0.962.633.578 (5)171
Symmetry codes: (i) x+1/2, y+1/2, z1/2; (ii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaC20H17ClN2O3
Mr368.81
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)8.6326 (9), 13.119 (1), 15.505 (4)
β (°) 96.19 (1)
V3)1745.7 (5)
Z4
Radiation typeMo Kα
µ (mm1)0.24
Crystal size (mm)0.36 × 0.2 × 0.14
Data collection
DiffractometerCAD4
diffractometer
Absorption correctionNumerical
integration (Sheldrick, 1976)
Tmin, Tmax0.91, 0.94
No. of measured, independent and
observed [I > 2σ(I)] reflections
3493, 3071, 1551
Rint0.031
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.132, 1.07
No. of reflections3071
No. of parameters235
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.22, 0.24

Computer programs: CAD-4-PC (Enraf Nonius, 1993), CAD-4-PC, MolEN (Fair, 1990), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), PARST (Nardelli, 1995), CSD (Allen et al., 1983) and WinGX (Farrugia, 1999).

Selected geometric parameters (Å, º) top
O1—C151.438 (4)N8—C71.361 (4)
O4—C41.221 (4)N8—C91.416 (4)
O7—C71.219 (4)C6—C71.519 (5)
N5—C41.377 (4)C12—Cl11.736 (4)
N5—C151.455 (4)C14—C151.515 (4)
N5—C61.462 (4)C15—C161.534 (4)
C4—N5—C15120.0 (3)O1—C15—N5109.1 (2)
C4—N5—C6119.7 (3)O1—C15—C14105.9 (3)
C15—N5—C6118.9 (3)N5—C15—C14109.0 (3)
C7—N8—C9122.0 (3)O1—C15—C16107.0 (2)
C7—N8—C8119.4 (3)N5—C15—C16113.7 (3)
C9—N8—C8118.7 (3)C14—C15—C16111.8 (2)
N5—C6—C7110.9 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C6—H6B···O40.972.332.760 (4)106
C8—H8C···O70.962.312.743 (5)106
C13—H13···O10.932.282.637 (4)102
C17—H17···N50.932.542.882 (4)102
C20—H20···O4i0.932.443.332 (5)161
C22—H22A···Cl1ii0.962.923.721 (4)142
C22—H22B···O7i0.962.633.578 (5)171
Symmetry codes: (i) x+1/2, y+1/2, z1/2; (ii) x, y+1, z.
 

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