2-(3-Oxo-3,4-dihydro-2H-1,4-benzo­thia­zin-4-yl)acetic acid monohydrate

Fun, H.-K.; Loh, W.-S.; Janardhana, G.; Khader, A.M.A.; Kalluraya, B.

doi:10.1107/S1600536809034977

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 10| October 2009| Pages o2358-o2359

doi:10.1107/S1600536809034977

Open

access

2-(3-Oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetic acid monohydrate

Hoong-Kun Fun,^a ^*‡ Wan-Sin Loh,^a G. Janardhana,^b A. M. A. Khader ^b and B. Kalluraya ^b

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^bDepartment of Studies in Chemistry, Mangalore University, Mangalagangothri, Mangalore 574 199, India
^*Correspondence e-mail: hkfun@usm.my

(Received 29 August 2009; accepted 31 August 2009; online 5 September 2009)

In the title compound, C₁₀H₉NO₃S·H₂O, the thiomorpholine ring exists in a conformation intermediate between twist-boat and half-chair. An intermolecular O—H⋯O hydrogen bond links the acid and water molecules together. In the crystal packing, intermolecular O—H⋯O and C—H⋯O hydrogen bonds link the molecules into a three-dimensional network.

Related literature

For the biological activity of 4H-benzo(1,4)thiazine, see: Armenise et al. (1991 ); Gupta et al. (1993 ); Fringuelli et al. (2005 ). For medical applications of sulfone derivatives of 4H-benzo(1,4)thiazine, see: Shinji & Koshiro (1995 ); Szule et al. (1988 ); Culbertson (1991 ). For a related structure, see: Zhang et al. (2008 ). For bond-length data, see: Allen et al. (1987 ). For ring puckering parameters, see: Cremer & Pople (1975 ). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₀H₉NO₃S·H₂O
M_r = 241.26
Monoclinic, P 2₁ /c
a = 7.5897 (1) Å
b = 9.2208 (2) Å
c = 15.6701 (3) Å
β = 94.336 (1)°
V = 1093.50 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.29 mm⁻¹
T = 100 K
0.49 × 0.34 × 0.11 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ) T_min = 0.870, T_max = 0.969
25955 measured reflections
4859 independent reflections
3833 reflections with I > 2σ(I)
R_int = 0.036

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.128
S = 0.83
4859 reflections
157 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.54 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H1O2⋯O1Wⁱ	0.93 (2)	1.62 (2)	2.5384 (13)	168 (3)
O1W—H2W1⋯O3ⁱⁱ	0.85 (2)	1.96 (2)	2.7893 (13)	168 (2)
O1W—H1W1⋯O1	0.90 (2)	1.85 (2)	2.7221 (13)	163.4 (19)
C2—H2A⋯O1Wⁱⁱⁱ	0.93	2.51	3.3666 (15)	153
C9—H9A⋯O2^iv	0.97	2.58	3.4429 (14)	149
Symmetry codes: (i) x+1, y, z; (ii) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) x, y-1, z; (iv) -x+2, -y+1, -z+1.

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809034977/sj2641sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809034977/sj2641Isup2.hkl

checkCIF report

Comment top

A number of molecules containing the 4H-benzo(1,4)thiazine nucleus in their structures exhibit a broad spectrum of biological activity, including antibacterial (Armenise et al., 1991), anticancer (Gupta et al., 1993), anti-rheumatic, anti-allergic, vasorelaxant, anti-arrhythmic and anti-hypertensive (Fringuelli et al., 2005) properties. The sulfone derivatives of 4H-benzo(1,4)thiazine have been reported to find a number of applications in medicine (Shinji & Koshiro, 1995; Szule et al., 1988; Culbertson, 1991). On the basis of these considerations, our particular attention was paid to the preparation of derivatives of (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetic acid and we report here the structure of the title 4-benzothiazine derivative.

The asymmetric unit of the title compound (Fig. 1), contains one (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetic acid and one water molecule. The bond lengths (Allen et al., 1987) and angles in the molecule are within normal ranges. The thiomorpholine ring (C1/C6–C8/N1/S1) exists in a conformation intermediate between twist-boat and half-chair and it is comparable to a closely related structure (Zhang et al., 2008). The puckering parameters (Cremer & Pople, 1975) are Q = 0.6852 (9) Å; Θ = 112.69 (8)° and ϕ = 152.79 (10)°. An intermolecular O1W1—H1W1···O1 hydrogen bond links the acid and water molecules together. In the crystal packing (Fig. 2), intermolecular O2—H1O2···O1W, O1W—H2W1···O3, C2—H2A···O1W and C9—H10A···O2 hydrogen bonds (Table 1) link the molecules into three-dimensional network.

Related literature top

For the biological activity of 4H-benzo(1,4)thiazine, see: Armenise et al. (1991); Gupta et al. (1993); Fringuelli et al. (2005). For medical applications of sulfone derivatives of 4H-benzo(1,4)thiazine, see: Shinji & Koshiro (1995); Szule et al. (1988); Culbertson (1991). For a related structure, see: Zhang et al. (2008). For bond-length data, see: Allen et al. (1987). For ring puckering parameters, see: Cremer & Pople (1975). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Experimental top

A solution of potassium hydroxide (5.85 mmol) in water (10 ml) was added to the solution of ethyl (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetate (3.9 mmol) in ethanol (10 ml). The resulting reaction mixture was stirred at room temperature for 24 h and the reaction completion was checked by TLC. The reaction mixture was poured into water and acidified with 4 M HCl to form (3-oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetic acid as colourless solid. Single crystals suitable for X-ray analysis were obtained by crystallization from dichloromethane under slow evaporation (M.p. 338 K).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom numbering scheme. The hydrogen bond is drawn as a dashed line.
	Fig. 2. The crystal packing of the title compound, viewed along b axis. Intermolecular hydrogen bonds are shown by dashed lines.

2-(3-Oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetic acid monohydrate top

Crystal data top

C₁₀H₉NO₃S·H₂O	F(000) = 504
M_r = 241.26	D_x = 1.465 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 7672 reflections
a = 7.5897 (1) Å	θ = 3.4–33.1°
b = 9.2208 (2) Å	µ = 0.29 mm⁻¹
c = 15.6701 (3) Å	T = 100 K
β = 94.336 (1)°	Block, colourless
V = 1093.50 (3) Å³	0.49 × 0.34 × 0.11 mm
Z = 4

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	4859 independent reflections
Radiation source: fine-focus sealed tube	3833 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
ϕ and ω scans	θ_max = 35.1°, θ_min = 2.6°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −12→12
T_min = 0.870, T_max = 0.969	k = −14→13
25955 measured reflections	l = −23→25

Refinement top

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.128	H atoms treated by a mixture of independent and constrained refinement
S = 0.83	w = 1/[σ²(F_o²) + (0.0915P)² + 0.3956P] where P = (F_o² + 2F_c²)/3
4859 reflections	(Δ/σ)_max = 0.001?
157 parameters	Δρ_max = 0.54 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₁₀H₉NO₃S·H₂O	V = 1093.50 (3) Å³
M_r = 241.26	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 7.5897 (1) Å	µ = 0.29 mm⁻¹
b = 9.2208 (2) Å	T = 100 K
c = 15.6701 (3) Å	0.49 × 0.34 × 0.11 mm
β = 94.336 (1)°

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	4859 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2005)	3833 reflections with I > 2σ(I)
T_min = 0.870, T_max = 0.969	R_int = 0.036
25955 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.128	H atoms treated by a mixture of independent and constrained refinement
S = 0.83	Δρ_max = 0.54 e Å⁻³
4859 reflections	Δρ_min = −0.26 e Å⁻³
157 parameters

Special details top

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

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 (Å²) top

	x	y	z	U_iso*/U_eq
S1	0.25290 (3)	0.20298 (3)	0.368735 (18)	0.02391 (8)
O1W	0.17478 (12)	0.72939 (10)	0.31220 (6)	0.02515 (17)
O1	0.47141 (12)	0.56427 (9)	0.33767 (6)	0.02699 (18)
O2	0.94362 (11)	0.62615 (9)	0.40417 (6)	0.02360 (16)
O3	0.90204 (12)	0.44113 (9)	0.31220 (6)	0.02548 (17)
C1	0.46033 (14)	0.11958 (11)	0.38793 (6)	0.01900 (18)
C2	0.47444 (16)	−0.03074 (12)	0.39590 (7)	0.0233 (2)
H2A	0.3733	−0.0879	0.3900	0.028*
C3	0.63845 (17)	−0.09543 (12)	0.41263 (7)	0.0247 (2)
H3A	0.6469	−0.1955	0.4193	0.030*
C4	0.78984 (16)	−0.01067 (12)	0.41946 (7)	0.0246 (2)
H4A	0.8999	−0.0544	0.4296	0.030*
C5	0.77815 (14)	0.13934 (12)	0.41127 (7)	0.02197 (19)
H5A	0.8801	0.1956	0.4156	0.026*
C6	0.61270 (13)	0.20523 (11)	0.39649 (6)	0.01770 (17)
N1	0.59863 (11)	0.35987 (9)	0.39215 (6)	0.01904 (16)
C7	0.46962 (14)	0.43038 (12)	0.34290 (7)	0.02067 (19)
C8	0.32911 (14)	0.33868 (13)	0.29697 (7)	0.0234 (2)
H8A	0.3764	0.2918	0.2482	0.028*
H8B	0.2309	0.3995	0.2760	0.028*
C9	0.73286 (14)	0.45083 (11)	0.43631 (7)	0.02047 (18)
H9A	0.7934	0.3959	0.4825	0.025*
H9B	0.6764	0.5333	0.4613	0.025*
C10	0.86713 (13)	0.50482 (11)	0.37642 (7)	0.01941 (18)
H1O2	1.028 (3)	0.652 (3)	0.3672 (15)	0.064 (7)*
H2W1	0.155 (3)	0.784 (2)	0.2691 (15)	0.056 (6)*
H1W1	0.270 (3)	0.672 (2)	0.3095 (13)	0.043 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
S1	0.01398 (12)	0.03081 (15)	0.02713 (14)	−0.00430 (9)	0.00291 (9)	0.00246 (9)
O1W	0.0185 (4)	0.0229 (4)	0.0340 (4)	0.0004 (3)	0.0017 (3)	0.0072 (3)
O1	0.0224 (4)	0.0214 (4)	0.0371 (5)	0.0033 (3)	0.0020 (3)	0.0071 (3)
O2	0.0222 (4)	0.0184 (3)	0.0304 (4)	−0.0051 (3)	0.0030 (3)	−0.0026 (3)
O3	0.0231 (4)	0.0232 (4)	0.0306 (4)	−0.0046 (3)	0.0049 (3)	−0.0046 (3)
C1	0.0179 (4)	0.0209 (4)	0.0184 (4)	−0.0039 (3)	0.0028 (3)	−0.0002 (3)
C2	0.0279 (5)	0.0217 (5)	0.0208 (4)	−0.0064 (4)	0.0046 (4)	−0.0016 (3)
C3	0.0358 (6)	0.0175 (4)	0.0211 (4)	−0.0004 (4)	0.0050 (4)	−0.0006 (3)
C4	0.0264 (5)	0.0226 (5)	0.0251 (5)	0.0052 (4)	0.0030 (4)	0.0020 (4)
C5	0.0169 (4)	0.0206 (4)	0.0284 (5)	0.0016 (3)	0.0019 (3)	0.0028 (4)
C6	0.0162 (4)	0.0169 (4)	0.0201 (4)	−0.0009 (3)	0.0022 (3)	0.0013 (3)
N1	0.0136 (3)	0.0176 (4)	0.0256 (4)	−0.0004 (3)	−0.0006 (3)	0.0029 (3)
C7	0.0150 (4)	0.0233 (5)	0.0239 (4)	0.0020 (3)	0.0027 (3)	0.0048 (3)
C8	0.0169 (4)	0.0296 (5)	0.0233 (5)	−0.0003 (4)	−0.0008 (3)	0.0047 (4)
C9	0.0172 (4)	0.0196 (4)	0.0243 (4)	−0.0020 (3)	−0.0001 (3)	0.0002 (3)
C10	0.0147 (4)	0.0169 (4)	0.0262 (5)	0.0000 (3)	−0.0009 (3)	0.0000 (3)

Geometric parameters (Å, º) top

S1—C1	1.7575 (11)	C4—C5	1.3914 (16)
S1—C8	1.8064 (12)	C4—H4A	0.9300
O1W—H2W1	0.85 (2)	C5—C6	1.3984 (15)
O1W—H1W1	0.90 (2)	C5—H5A	0.9300
O1—C7	1.2374 (13)	C6—N1	1.4311 (13)
O2—C10	1.3189 (13)	N1—C7	1.3648 (13)
O2—H1O2	0.93 (3)	N1—C9	1.4539 (13)
O3—C10	1.2116 (14)	C7—C8	1.5014 (16)
C1—C2	1.3951 (15)	C8—H8A	0.9700
C1—C6	1.3985 (14)	C8—H8B	0.9700
C2—C3	1.3873 (17)	C9—C10	1.5205 (16)
C2—H2A	0.9300	C9—H9A	0.9700
C3—C4	1.3871 (17)	C9—H9B	0.9700
C3—H3A	0.9300

C1—S1—C8	94.86 (5)	C7—N1—C6	123.32 (9)
H2W1—O1W—H1W1	114 (2)	C7—N1—C9	116.19 (8)
C10—O2—H1O2	108.8 (14)	C6—N1—C9	120.33 (8)
C2—C1—C6	119.68 (10)	O1—C7—N1	120.11 (10)
C2—C1—S1	120.78 (8)	O1—C7—C8	122.76 (10)
C6—C1—S1	119.53 (8)	N1—C7—C8	117.12 (9)
C3—C2—C1	120.38 (10)	C7—C8—S1	109.94 (7)
C3—C2—H2A	119.8	C7—C8—H8A	109.7
C1—C2—H2A	119.8	S1—C8—H8A	109.7
C4—C3—C2	119.90 (10)	C7—C8—H8B	109.7
C4—C3—H3A	120.0	S1—C8—H8B	109.7
C2—C3—H3A	120.0	H8A—C8—H8B	108.2
C3—C4—C5	120.42 (11)	N1—C9—C10	111.92 (9)
C3—C4—H4A	119.8	N1—C9—H9A	109.2
C5—C4—H4A	119.8	C10—C9—H9A	109.2
C4—C5—C6	119.83 (10)	N1—C9—H9B	109.2
C4—C5—H5A	120.1	C10—C9—H9B	109.2
C6—C5—H5A	120.1	H9A—C9—H9B	107.9
C1—C6—C5	119.75 (9)	O3—C10—O2	124.51 (10)
C1—C6—N1	119.99 (9)	O3—C10—C9	123.56 (9)
C5—C6—N1	120.24 (9)	O2—C10—C9	111.90 (9)

C8—S1—C1—C2	−142.00 (9)	C5—C6—N1—C7	149.31 (11)
C8—S1—C1—C6	38.91 (9)	C1—C6—N1—C9	152.60 (10)
C6—C1—C2—C3	0.30 (16)	C5—C6—N1—C9	−25.91 (14)
S1—C1—C2—C3	−178.80 (8)	C6—N1—C7—O1	−175.33 (10)
C1—C2—C3—C4	−1.55 (16)	C9—N1—C7—O1	0.07 (15)
C2—C3—C4—C5	1.24 (17)	C6—N1—C7—C8	4.85 (15)
C3—C4—C5—C6	0.33 (17)	C9—N1—C7—C8	−179.75 (9)
C2—C1—C6—C5	1.27 (15)	O1—C7—C8—S1	−134.43 (10)
S1—C1—C6—C5	−179.63 (8)	N1—C7—C8—S1	45.39 (12)
C2—C1—C6—N1	−177.25 (9)	C1—S1—C8—C7	−60.65 (8)
S1—C1—C6—N1	1.86 (13)	C7—N1—C9—C10	−77.23 (12)
C4—C5—C6—C1	−1.58 (16)	C6—N1—C9—C10	98.32 (11)
C4—C5—C6—N1	176.93 (10)	N1—C9—C10—O3	−26.48 (14)
C1—C6—N1—C7	−32.18 (15)	N1—C9—C10—O2	155.33 (9)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O1Wⁱ	0.93 (2)	1.62 (2)	2.5384 (13)	168 (3)
O1W—H2W1···O3ⁱⁱ	0.85 (2)	1.96 (2)	2.7893 (13)	168 (2)
O1W—H1W1···O1	0.90 (2)	1.85 (2)	2.7221 (13)	163.4 (19)
C2—H2A···O1Wⁱⁱⁱ	0.93	2.51	3.3666 (15)	153
C9—H9A···O2^iv	0.97	2.58	3.4429 (14)	149

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

Experimental details

Crystal data
Chemical formula	C₁₀H₉NO₃S·H₂O
M_r	241.26
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	7.5897 (1), 9.2208 (2), 15.6701 (3)
β (°)	94.336 (1)
V (Å³)	1093.50 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.29
Crystal size (mm)	0.49 × 0.34 × 0.11

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2005)
T_min, T_max	0.870, 0.969
No. of measured, independent and observed [I > 2σ(I)] reflections	25955, 4859, 3833
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.809

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.128, 0.83
No. of reflections	4859
No. of parameters	157
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.54, −0.26

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O1Wⁱ	0.93 (2)	1.62 (2)	2.5384 (13)	168 (3)
O1W—H2W1···O3ⁱⁱ	0.85 (2)	1.96 (2)	2.7893 (13)	168 (2)
O1W—H1W1···O1	0.90 (2)	1.85 (2)	2.7221 (13)	163.4 (19)
C2—H2A···O1Wⁱⁱⁱ	0.9300	2.5100	3.3666 (15)	153.00
C9—H9A···O2^iv	0.9700	2.5800	3.4429 (14)	149.00

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

Footnotes

‡Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

HKF thanks Universiti Sains Malaysia (USM) for the Research University Golden Goose Grant (No. 1001/PFIZIK/811012). WSL thanks the Malaysian government and USM for the award of the post of Assistant Research Officer under the Research University Golden Goose Grant (No. 1001/PFIZIK/811012).

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. CrossRef Web of Science Google Scholar
Armenise, D., Trapani, G., Arrivo, V. & Morlacchi, F. (1991). Farmaco. 46, 1023–1032. PubMed CAS Web of Science Google Scholar
Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107. CrossRef CAS Web of Science IUCr Journals Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Culbertson, T. P. (1991). J. Heterocycl. Chem. 28, 1701–1708. CrossRef CAS Google Scholar
Fringuelli, R., Milanese, L. & Schiaffella, F. (2005). Mini-Rev. Med. Chem. 5, 1061–1073(13). Web of Science CrossRef CAS Google Scholar
Gupta, R. R., Dev, P. K., Sharma, M. L., Rajoria, C. M., Gupta, A. & Nyati, M. (1993). Anti-Ca. Drugs. 4, 589–592. CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Shinji, S. & Koshiro, A. (1995). Biol. Pharm. Bull. 18, 586–594. PubMed Web of Science Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Szule, Z., Mlochow, J. & Palus, J. (1988). J. Prakt. Chem. 330, 1023–1028. Google Scholar
Zhang, P., Du, N., Wang, L.-Z. & Li, Y. (2008). Acta Cryst. E64, o746. Web of Science CSD CrossRef IUCr Journals Google Scholar