I. INTRODUCTION
Thiamphenicol (Figure 1), systematic name 2, 2-dichloro-N-[(1R, 2R)-2-hydroxy -1- (hydroxymethyl)-2-[4-(methylsulfonyl) phenyl] ethyl] acetamide, is a synthetic derivative of chloramphenicol (Shin and Kim, Reference Shin and Kim1983). It has been reported that thiamphenicol possesses a variety of therapeutic effects in respiratory infections, bacterial prostatitis, and venereal diseases (Ma et al., Reference Ma, Chen, Sun, Ye and Chen2012). Compared with other chloramphenicol antibiotics, thiamphenicol has a similar antibacterial spectrum, satisfactory pharmacokinetic characteristics and less toxic with high bioavailability. Therefore, thiamphenicol has the potential to be a substitution for other chloramphenicol antibiotics in clinical trials (Kowalski, Reference Kowalski2007).
Figure 1. Structural formula of thiamphenicol.
The atomic structure based on single-crystal data of thiamphenicol were reported by Shin and Kim (Reference Shin and Kim1983) and Ghosh et al. (Reference Ghosh, Basak and Mazumdar1987), recorded separately in Powder Diffraction File (PDF)-4/Organic 2015 database with the PDF numbers 02-060-8605 and 02-060-8606. The average values of cell parameters were a = 5.780(1), b = 15.307(7), c = 17.329(7) Å, α = β = γ = 90°, unit-cell volume V = 1533.2(7) Å3, Z = 4, and space group P212121. The experimental pattern 00-057-1620 found in PDF™ is unindexed. The detailed X-ray powder diffraction (XRD) data for thiamphenicol have not been reported in the literature so far.
II. EXPERIMENTAL
A. Sample preparation
The title compound (98% purity) was supplied by DaLian MeiLun Biology Technology Co., Ltd. It was recrystallized by slow evaporation of an ethanol solution (analytical grade) at room temperature. The sample was placed in a vacuum drying oven, and the drying temperature was kept under 50 °C . The physical nature of the compound was characterized by melting point at 164 °C, density at 1.596 g cm−3, and microscope measurements. The sample was ground into powder and sieved through 200-mesh screening.
B. Diffraction data collection and reduction
The XRD data were recorded using an X'Pert PRO diffractometer (PANalytical Co., Ltd., Netherlands) equipped with a PIXcel one-dimensional detector and CuKα 1 radiation (λ = 1.540 56 Å, generator setting: 40 kV and 40 mA). The diffractometer was operated in the angular range from 4 to 60°2θ with a step size of 0.013 13°2θ and a counting time of 90 ms step−1. All data were collected in the constant environments at a controlled relative humidity of 60% and a controlled temperature of 25 °C.
The structural calculations were mostly conducted using the Reflex module in the software package Material Studio 4.2 (Accelrys Co., Ltd., USA) in the State Key Laboratory of Polymer Materials Engineering (Sichuan University, China). The resulting diffractogram was analyzed using various mathematical treatments. To improve the resolution in the calculation processing, the diffractogram should be smoothed before any subsequent processing by removing overlapping peaks and correcting the baseline. Subsequently, the background was subtracted and the Kα 2 component was eliminated. Automatic indexing of the pretreated experimental XRD pattern was done using DICVOL91 (LoueÈr et al., Reference LoueÈr and LoueÈr1972; Boultif and LoueÈr, Reference Boultif and LoueÈr1991). The best result obtained in the indexing of the first 23 peaks of this pattern was an orthorhombic unit cell, which is consistent with the result reported by Shin and Kim (Reference Shin and Kim1983) and Ghosh et al. (Reference Ghosh, Basak and Mazumdar1987). Then the unit-cell parameters were refined using the Pawley method (Pan et al., Reference Pan, Guo, Duan, Cheng and Li2012; Tang et al., Reference Tang, Wu, Zhang, Cheng and Li2013) resulting in final R wp of the structure was converged at 4.61%.
III. RESULTS
The experimental powder diffraction pattern is depicted in Figure 2. With this pattern, the relative intensity (1000 = maximum) is plotted against 2θ in order to better compare with the PDF. Table I gives the 2θ , d-spacing, relative intensity and hkl for each observed line. The figures of merit are F 23 = 67.0 (0.0067, 51) (Smith and Snyder, Reference Smith and Snyder1979) and M 23 = 33.8 (de Wolff, Reference de Wolff1968). Indexing results confirmed that thiamphenicol is orthorhombic with space group P212121 and unit-cell parameters after Pawley refinement are: a = 17.346(3) Å, b = 15.341(0) Å, c = 5.790 (2) Å, α = β = γ = 90°, unit-cell volume V = 1540.8(3) Å3, and Z = 4. A comparison of the unit-cell parameters from powder data and single-crystal data (Shin and Kim, Reference Shin and Kim1983; Ghosh et al., Reference Ghosh, Basak and Mazumdar1987) displays a significant consistency, and the relative difference in d-spacings of the two patterns compared with the pattern reported here were between 0.096 and 0.493%. The experiment diffraction peaks and d-spacings were consistent with this pattern that provided in PDF 02-060-8605 and 02-060-8606. All lines were indexed and are consistent with the P212121 space group.
Figure 2. XRD pattern of the thiamphenicol recrystallized in ethanol, using CuKα 1 radiation (λ = 1.540 56 Å).
Table I. XRD data of thiamphenicol recrystallized in ethanol. All measured lines were indexed and are consistent with the P212121 space group. The d-values were calculated using CuKα 1 radiation (λ = 1.54056 Å).
SUPPLEMENTARY MATERIALS AND METHODS
The supplementary material for this article can be found at http://dx.doi.org/10.1017/S0885715615000834
ACKNOWLEDGEMENTS
This work was supported by the Applied Basic Research Project of Sichuan Province (Grant No. 2014JY0042).
