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Acta Cryst. (2011). E67, o1727-o1728    [ doi:10.1107/S1600536811022768 ]

1-(1-Hydroxyethyl)-7,8-dihydroindolo[2,3-a]pyridine[3,4-g]quinolizin-5(13H)-one (angustoline) monohydrate from Nauclea subdita (Rubiaceae)

S. Y. Liew, M. R. Mukhtar, K. Awang, M. R. Mustafa and S. W. Ng

Abstract top

The title compound (trivial name: angustoline monohydrate), C20H17N3O2·H2O, features a fused-ring system formed by one five- and four six-membered rings. The nearly planar benzimidazole portion (r.m.s. deviation = 0.008 Å) and the nearly planar 2,7-naphthyridin-1-one portion (r.m.s. deviation = 0.022 Å) of the fused-ring system are slightly twisted, with a dihedral angle of 9.47 (8)°, owing to the tetrahedral nature of the two methylene linkages in the central six-membered ring. The secondary N atom acts as a hydrogen-bond donor to the water molecule of crystallization. In the crystal, the amino and hydroxy groups, and the water molecule are engaged in hydrogen bonding, generating a three-dimensional network.

Comment top

The alkaloid angustoline has been isolated from a number of plants: Camptotheca acuminata (Carte et al., 1990; Lin et al., 1988), Nauclea latifolia (Kakuguchi et al., 2009; Hotellier et al., 1975), Nauclea officinalis (Fan et al., 2010; Sun et al., 2008; Xuan et al., 2007), Nauclea orientalis (Erdelmeier et al., 1992), Nauclea pobeguinii (Zeches et al., 1985), Sarcocephalus latifolius (Abreu & Pereira, 1998; 2001) and Strychnos angustiflora (Au et al., 1973).

The alkaloid is isolated in the crystalline form as a monohydrate (Scheme I). The planar benzimidazole portion and the planar 2,7-naphthyridin-1-one portion of the fused-ring system are slightly twisted [dihedral angle 9.47 (8)°] owing to the tetrahedral nature of the two methylene linkages (Fig. 1). The secondary N atom is hydrogen-bond donor to the water molecule. The amino and hydroxy groups, and the lattice water molecule are engaged in hydrogen bonding to furnish a three-dimensional network (Table 1).

Related literature top

For the isolation of the title compound from other plants, see: Abreu & Pereira (1998, 2001); Au et al. (1973); Carte et al. (1990); Erdelmeier et al. (1992); Fan et al. (2010); Hotellier et al. (1975); Kakuguchi et al. (2009); Lin et al. (1988); Sun et al. (2008); Xuan et al. (2007); Zeches et al. (1985).

Experimental top

Nauclea subdita (Rubiaceae) was collected from Bukit Kinta forest reserve, Chemor, Perak, Malaysia, and specimens were deposited at the Herbarium, Department of Chemistry, University of Malaya.

Dried and ground bark of Nauclea subdita (1.7 kg) was extracted with hexane (17 L) for 3 days. The hexane extract was concentrated under reduced pressure. The dried plant material was soaked in ammonium hydroxide for 2 h. It was further extracted with dichloromethane (17 L) for 3 days. The dichloromethane extract was concentrated under reduced pressure to give a crude alkaloid (7.1 g). A portion (6.0 g) was subjected to column chromatography on silica gel 60 GF254 by using a step gradient of dichloromethane and methanol. One of the fractions when further purified by using dichloromethane/methanol (95:5) afforded the pure compound, whose formulation was established by NMR spectroscopic analysis.

Refinement top

Carbon-bound H-atoms were placed in calculated positions [C—H 0.95 to 0.99 Å, Uiso(H) 1.2 to 1.5Ueq(C)] and were included in the refinement in the riding model approximation.

The nitrogen and oxygen bound H-atoms were located in a difference Fourier map, and were freely refined.

The Flack parameter was determined from 1395 Friedel pairs.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO (Agilent, 2010); data reduction: CrysAlis PRO (Agilent, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of C20H17N3O2.H2O at the 70% probability level; hydrogen atoms are drawn as spheres of arbitrary radius.
1-(1-Hydroxyethyl)-7,8-dihydroindolo[2,3-a]pyridine[3,4- g]quinolizin-5(13H)-one monohydrate top
Crystal data top
C20H17N3O2·H2OF(000) = 368
Mr = 349.38Dx = 1.366 Mg m−3
Monoclinic, P21Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2ybCell parameters from 3352 reflections
a = 8.8350 (3) Åθ = 3.1–74.0°
b = 6.7002 (2) ŵ = 0.76 mm−1
c = 14.7347 (4) ÅT = 100 K
β = 103.117 (3)°Prism, yellow
V = 849.48 (4) Å30.30 × 0.03 × 0.03 mm
Z = 2
Data collection top
Agilent SuperNova Dual with an Atlas detector
diffractometer		3252 independent reflections
Radiation source: SuperNova (Cu) X-ray Source3015 reflections with I > 2σ(I)
MirrorRint = 0.027
Detector resolution: 10.4041 pixels mm-1θmax = 74.2°, θmin = 3.1°
ω scansh = −11→9
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)		k = −7→8
Tmin = 0.803, Tmax = 0.978l = −17→18
6453 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.036H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098 w = 1/[σ2(Fo2) + (0.0647P)2 + 0.0395P]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max = 0.001
3252 reflectionsΔρmax = 0.29 e Å−3
251 parametersΔρmin = −0.23 e Å−3
1 restraintAbsolute structure: Flack (1983), 1395 Friedel pairs
Primary atom site location: structure-invariant direct methodsFlack parameter: 0.1 (2)
Crystal data top
C20H17N3O2·H2OV = 849.48 (4) Å3
Mr = 349.38Z = 2
Monoclinic, P21Cu Kα radiation
a = 8.8350 (3) ŵ = 0.76 mm−1
b = 6.7002 (2) ÅT = 100 K
c = 14.7347 (4) Å0.30 × 0.03 × 0.03 mm
β = 103.117 (3)°
Data collection top
Agilent SuperNova Dual with an Atlas detector
diffractometer		3252 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2010)		3015 reflections with I > 2σ(I)
Tmin = 0.803, Tmax = 0.978Rint = 0.027
6453 measured reflectionsθmax = 74.2°
Refinement top
R[F2 > 2σ(F2)] = 0.036H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098Δρmax = 0.29 e Å−3
S = 1.02Δρmin = −0.23 e Å−3
3252 reflectionsAbsolute structure: Flack (1983), 1395 Friedel pairs
251 parametersFlack parameter: 0.1 (2)
1 restraint
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.33730 (17)0.5046 (2)0.78985 (11)0.0309 (3)
O20.76411 (17)0.6678 (2)0.44802 (9)0.0280 (3)
H20.677 (4)0.578 (5)0.429 (2)0.061 (9)*
O1W1.0970 (2)0.2216 (3)0.70030 (13)0.0384 (4)
H111.157 (4)0.316 (6)0.725 (2)0.060 (10)*
H121.125 (4)0.196 (6)0.652 (2)0.063 (10)*
N10.89459 (18)0.0009 (2)0.78964 (11)0.0210 (3)
H10.953 (3)0.071 (4)0.7637 (15)0.022 (6)*
N20.54310 (19)0.2982 (2)0.79266 (12)0.0234 (3)
N30.4603 (2)0.8811 (3)0.59777 (12)0.0280 (4)
C10.9248 (2)−0.1772 (3)0.83570 (12)0.0212 (4)
C21.0553 (2)−0.3025 (3)0.84619 (13)0.0238 (4)
H2A1.1403−0.26940.81950.029*
C31.0547 (2)−0.4757 (3)0.89683 (12)0.0245 (4)
H31.1405−0.56440.90400.029*
C40.9304 (2)−0.5250 (3)0.93830 (12)0.0256 (4)
H40.9340−0.64520.97290.031*
C50.8035 (2)−0.3999 (3)0.92892 (12)0.0236 (4)
H50.7204−0.43280.95740.028*
C60.7989 (2)−0.2238 (3)0.87687 (12)0.0214 (4)
C70.6920 (2)−0.0637 (3)0.85452 (13)0.0218 (4)
C80.5381 (2)−0.0264 (3)0.87749 (14)0.0250 (4)
H8A0.5377−0.08130.93980.030*
H8B0.4545−0.09240.83110.030*
C90.5108 (2)0.1974 (3)0.87643 (14)0.0280 (4)
H9A0.40150.22290.87890.034*
H9B0.57810.25660.93300.034*
C100.6769 (2)0.2496 (3)0.76131 (13)0.0209 (4)
C110.7537 (2)0.0699 (3)0.80190 (12)0.0214 (4)
C120.7238 (2)0.3627 (3)0.69551 (13)0.0205 (4)
H12A0.81310.32450.67400.025*
C130.6401 (2)0.5366 (3)0.65911 (12)0.0207 (4)
C140.5043 (2)0.5833 (3)0.69001 (13)0.0224 (4)
C150.4529 (2)0.4620 (3)0.75959 (13)0.0238 (4)
C160.4187 (2)0.7539 (3)0.65684 (13)0.0250 (4)
H160.32630.78020.67750.030*
C170.5887 (2)0.8336 (3)0.56645 (13)0.0274 (4)
H170.61790.92200.52300.033*
C180.6799 (2)0.6681 (3)0.59251 (12)0.0230 (4)
C190.8136 (2)0.6270 (3)0.54537 (13)0.0260 (4)
H190.84210.48260.55370.031*
C200.9565 (3)0.7508 (4)0.58426 (16)0.0396 (5)
H20A1.03800.71780.55140.059*
H20B0.99380.72200.65080.059*
H20C0.93060.89280.57580.059*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0278 (7)0.0272 (7)0.0445 (8)0.0050 (6)0.0228 (6)0.0025 (6)
O20.0305 (7)0.0321 (7)0.0238 (7)−0.0063 (6)0.0114 (6)0.0003 (6)
O1W0.0409 (9)0.0419 (10)0.0405 (9)−0.0122 (7)0.0261 (7)−0.0102 (7)
N10.0210 (7)0.0209 (8)0.0245 (7)0.0005 (6)0.0125 (6)0.0017 (6)
N20.0229 (8)0.0223 (8)0.0300 (8)0.0018 (6)0.0161 (6)0.0006 (6)
N30.0267 (9)0.0310 (10)0.0272 (8)0.0079 (7)0.0081 (7)0.0055 (7)
C10.0232 (9)0.0216 (9)0.0197 (8)−0.0019 (7)0.0068 (7)−0.0023 (7)
C20.0233 (9)0.0278 (10)0.0222 (8)0.0038 (7)0.0089 (7)−0.0024 (7)
C30.0263 (9)0.0255 (10)0.0218 (8)0.0061 (7)0.0057 (7)−0.0009 (7)
C40.0324 (10)0.0217 (10)0.0234 (9)0.0005 (8)0.0080 (8)0.0014 (7)
C50.0268 (9)0.0231 (9)0.0233 (8)−0.0033 (8)0.0107 (7)−0.0011 (7)
C60.0215 (8)0.0225 (9)0.0218 (8)−0.0013 (7)0.0081 (7)−0.0036 (7)
C70.0232 (9)0.0207 (9)0.0243 (8)−0.0015 (7)0.0109 (7)−0.0025 (7)
C80.0239 (9)0.0218 (10)0.0337 (10)0.0013 (7)0.0161 (7)0.0023 (8)
C90.0323 (10)0.0241 (10)0.0344 (10)0.0022 (8)0.0222 (9)0.0029 (8)
C100.0206 (8)0.0194 (9)0.0255 (9)0.0002 (7)0.0114 (7)−0.0032 (7)
C110.0218 (8)0.0205 (9)0.0248 (8)0.0004 (7)0.0112 (7)−0.0049 (7)
C120.0189 (8)0.0222 (10)0.0232 (8)0.0002 (7)0.0105 (7)−0.0024 (7)
C130.0188 (8)0.0248 (10)0.0198 (8)−0.0010 (7)0.0070 (7)−0.0036 (6)
C140.0204 (8)0.0242 (9)0.0240 (8)−0.0003 (7)0.0082 (7)−0.0011 (7)
C150.0224 (9)0.0214 (10)0.0305 (9)0.0003 (7)0.0122 (7)−0.0026 (7)
C160.0218 (9)0.0287 (10)0.0266 (9)0.0021 (7)0.0101 (7)−0.0002 (8)
C170.0273 (10)0.0328 (11)0.0233 (9)0.0028 (8)0.0086 (8)0.0062 (7)
C180.0223 (9)0.0277 (10)0.0201 (8)−0.0006 (7)0.0073 (7)−0.0015 (8)
C190.0251 (9)0.0320 (11)0.0235 (8)0.0017 (7)0.0107 (7)0.0020 (7)
C200.0277 (10)0.0625 (15)0.0319 (11)−0.0070 (10)0.0134 (8)−0.0115 (10)
Geometric parameters (Å, °) top
O1—C151.237 (2)C7—C111.375 (3)
O2—C191.428 (2)C7—C81.495 (2)
O2—H20.97 (4)C8—C91.518 (3)
O1W—H110.85 (4)C8—H8A0.9900
O1W—H120.83 (4)C8—H8B0.9900
N1—C11.369 (2)C9—H9A0.9900
N1—C111.378 (2)C9—H9B0.9900
N1—H10.85 (3)C10—C121.366 (2)
N2—C151.379 (3)C10—C111.443 (3)
N2—C101.402 (2)C12—C131.419 (3)
N2—C91.490 (2)C12—H12A0.9500
N3—C161.328 (3)C13—C141.412 (2)
N3—C171.356 (3)C13—C181.421 (3)
C1—C21.406 (3)C14—C161.396 (3)
C1—C61.418 (2)C14—C151.459 (3)
C2—C31.380 (3)C16—H160.9500
C2—H2A0.9500C17—C181.373 (3)
C3—C41.412 (3)C17—H170.9500
C3—H30.9500C18—C191.525 (2)
C4—C51.381 (3)C19—C201.511 (3)
C4—H40.9500C19—H191.0000
C5—C61.403 (3)C20—H20A0.9800
C5—H50.9500C20—H20B0.9800
C6—C71.418 (3)C20—H20C0.9800
C19—O2—H2102.3 (19)H9A—C9—H9B107.7
H11—O1W—H12104 (3)C12—C10—N2121.26 (17)
C1—N1—C11107.94 (15)C12—C10—C11124.55 (16)
C1—N1—H1129.4 (16)N2—C10—C11114.15 (15)
C11—N1—H1122.2 (16)C7—C11—N1109.94 (17)
C15—N2—C10122.12 (15)C7—C11—C10124.60 (16)
C15—N2—C9116.72 (15)N1—C11—C10125.37 (16)
C10—N2—C9120.11 (16)C10—C12—C13120.54 (16)
C16—N3—C17116.71 (17)C10—C12—H12A119.7
N1—C1—C2129.66 (17)C13—C12—H12A119.7
N1—C1—C6108.67 (16)C14—C13—C12117.92 (16)
C2—C1—C6121.66 (17)C14—C13—C18116.52 (17)
C3—C2—C1117.27 (17)C12—C13—C18125.56 (16)
C3—C2—H2A121.4C16—C14—C13120.08 (16)
C1—C2—H2A121.4C16—C14—C15118.13 (16)
C2—C3—C4121.95 (17)C13—C14—C15121.74 (17)
C2—C3—H3119.0O1—C15—N2120.96 (17)
C4—C3—H3119.0O1—C15—C14122.63 (18)
C5—C4—C3120.55 (18)N2—C15—C14116.38 (16)
C5—C4—H4119.7N3—C16—C14123.12 (16)
C3—C4—H4119.7N3—C16—H16118.4
C4—C5—C6119.14 (17)C14—C16—H16118.4
C4—C5—H5120.4N3—C17—C18125.27 (19)
C6—C5—H5120.4N3—C17—H17117.4
C5—C6—C1119.41 (17)C18—C17—H17117.4
C5—C6—C7134.32 (17)C17—C18—C13118.21 (17)
C1—C6—C7106.26 (16)C17—C18—C19118.98 (17)
C11—C7—C6107.19 (16)C13—C18—C19122.73 (17)
C11—C7—C8121.06 (17)O2—C19—C20108.34 (17)
C6—C7—C8131.75 (17)O2—C19—C18109.32 (16)
C7—C8—C9108.24 (15)C20—C19—C18113.28 (16)
C7—C8—H8A110.1O2—C19—H19108.6
C9—C8—H8A110.1C20—C19—H19108.6
C7—C8—H8B110.1C18—C19—H19108.6
C9—C8—H8B110.1C19—C20—H20A109.5
H8A—C8—H8B108.4C19—C20—H20B109.5
N2—C9—C8113.37 (16)H20A—C20—H20B109.5
N2—C9—H9A108.9C19—C20—H20C109.5
C8—C9—H9A108.9H20A—C20—H20C109.5
N2—C9—H9B108.9H20B—C20—H20C109.5
C8—C9—H9B108.9
C11—N1—C1—C2−177.98 (19)N2—C10—C11—C710.4 (3)
C11—N1—C1—C60.94 (19)C12—C10—C11—N18.9 (3)
N1—C1—C2—C3−179.93 (17)N2—C10—C11—N1−173.35 (17)
C6—C1—C2—C31.3 (3)N2—C10—C12—C131.9 (3)
C1—C2—C3—C4−1.2 (3)C11—C10—C12—C13179.54 (17)
C2—C3—C4—C50.3 (3)C10—C12—C13—C14−2.7 (3)
C3—C4—C5—C60.6 (3)C10—C12—C13—C18178.32 (18)
C4—C5—C6—C1−0.5 (3)C12—C13—C14—C16179.44 (17)
C4—C5—C6—C7−178.7 (2)C18—C13—C14—C16−1.5 (3)
N1—C1—C6—C5−179.48 (16)C12—C13—C14—C152.1 (3)
C2—C1—C6—C5−0.5 (3)C18—C13—C14—C15−178.81 (17)
N1—C1—C6—C7−0.8 (2)C10—N2—C15—O1−178.32 (18)
C2—C1—C6—C7178.23 (17)C9—N2—C15—O1−10.0 (3)
C5—C6—C7—C11178.7 (2)C10—N2—C15—C14−0.1 (3)
C1—C6—C7—C110.3 (2)C9—N2—C15—C14168.16 (17)
C5—C6—C7—C8−1.8 (4)C16—C14—C15—O10.0 (3)
C1—C6—C7—C8179.82 (19)C13—C14—C15—O1177.41 (18)
C11—C7—C8—C9−26.5 (3)C16—C14—C15—N2−178.11 (18)
C6—C7—C8—C9154.1 (2)C13—C14—C15—N2−0.7 (3)
C15—N2—C9—C8147.19 (18)C17—N3—C16—C143.0 (3)
C10—N2—C9—C8−44.3 (3)C13—C14—C16—N3−1.6 (3)
C7—C8—C9—N247.4 (2)C15—C14—C16—N3175.87 (18)
C15—N2—C10—C12−0.5 (3)C16—N3—C17—C18−1.5 (3)
C9—N2—C10—C12−168.38 (18)N3—C17—C18—C13−1.4 (3)
C15—N2—C10—C11−178.32 (17)N3—C17—C18—C19175.34 (19)
C9—N2—C10—C1113.8 (2)C14—C13—C18—C172.8 (3)
C6—C7—C11—N10.2 (2)C12—C13—C18—C17−178.17 (18)
C8—C7—C11—N1−179.32 (17)C14—C13—C18—C19−173.81 (17)
C6—C7—C11—C10176.94 (17)C12—C13—C18—C195.2 (3)
C8—C7—C11—C10−2.6 (3)C17—C18—C19—O2−41.1 (2)
C1—N1—C11—C7−0.7 (2)C13—C18—C19—O2135.53 (18)
C1—N1—C11—C10−177.41 (17)C17—C18—C19—C2079.8 (2)
C12—C10—C11—C7−167.33 (19)C13—C18—C19—C20−103.6 (2)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O2—H2···N3i0.97 (4)1.77 (4)2.732 (2)171 (3)
O1w—H11···O1ii0.85 (4)2.08 (4)2.928 (2)169 (3)
O1w—H12···O2iii0.83 (4)1.95 (4)2.762 (2)167 (3)
N1—H1···O1w0.85 (3)2.02 (3)2.861 (2)177 (2)
Symmetry codes: (i) −x+1, y−1/2, −z+1; (ii) x+1, y, z; (iii) −x+2, y−1/2, −z+1.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O2—H2···N3i0.97 (4)1.77 (4)2.732 (2)171 (3)
O1w—H11···O1ii0.85 (4)2.08 (4)2.928 (2)169 (3)
O1w—H12···O2iii0.83 (4)1.95 (4)2.762 (2)167 (3)
N1—H1···O1w0.85 (3)2.02 (3)2.861 (2)177 (2)
Symmetry codes: (i) −x+1, y−1/2, −z+1; (ii) x+1, y, z; (iii) −x+2, y−1/2, −z+1.
Acknowledgements top

This work was carried under the aegis of a University of Malaya–CNRS (France) collaborative framework. We thank the Ministry of Higher Education (grant No. FRGS-FP016/2010 A) for financial support.

references
References top

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