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In recent years, in the course of pharmaceuticals purified, as the need to chiral purification decreased since the improving of the asymmetric synthetic techniques, the desire to make medicine effective yet with a smaller number of doses and promised safety has raised
"Chiral CD-Ph" is silica-based chiral packing material modified by phenyl-carbamated β-cyclodextrin (CD) as the enantiomer selector. Chiral CD-Ph is useful for the chiral separation of the racemic substance with benzene ring in its structure. It has superior capacity of chiral recognition derived from balanced hydrophobicity and polarity from the phenyl carbamate and the inclusion function from the central cavity in the structure of cyclodextrin. In addition, Chiral CD-Ph is applicable in both of the normal-phase and reversed-phase mode; hence enable to provide separation conditions best matching the solubility of different samples. Chiral CD-Ph column is easy-to-use with excellent durability.
In recent years, in the course of pharmaceuticals purified, as the need to chiral purification decreased since the improving of the asymmetric synthetic techniques, the desire to make medicine effective yet with a smaller number of doses and promised safety has raised. In response, complicated drug design has become more necessary. Against this background, chiral separation has become an essential technique for the development of high value-added agents.
Shiseido succeeded in the development of packing material Chiral CD-Ph from a precisely classified high-purity spherical silica with phenyl-carbamated β-cyclodextrin chemically bonded as a chiral selector. The Chiral CD-Ph column is designated as one of USP parking L45. In this report, the basic characteristic of Chiral CD-Ph is reported with the applications in the separation of enantiomers and the durability evaluation.
1. Synthesis of Chiral CD-Ph
The packing material Chiral CD-Ph was synthesized by the following steps.
The synthesized chiral β-cyclodextrin is shown in Figure 1. The phenyl-carbamated β-cyclodextrin (CD) is bonded to base silica as the chiral selector via a spacer. The balance between the hydrophobicity and polarity of phenylcarbamate assures sample retention, and the central cavity of β-cyclodextrin presents excellent chiral recognition with inclusion.
Figure 1: Structure of Chiral CD-Ph.
2. Applications in chiral separations
1) Chiral separation under-phase normal-phase mode.
Neutral compound hexobarbital was separated under C2H5OH / n-hexane = 40 / 60. The chromatogram is shown in Figure. 2. Good separation and peak shape are obtained.
Figure 2: Chiral separation of Hexobarbital.
2) Application in reverse-phase separation
Figure 3: Chiral separation of Carvone.
The neutral compound of carvone was separated under mobile phase of CH3OH / H2O = 70 / 30, whereas, the basic compounds of norfenefrine and atropine were separated under 0.5 mol/L NaClO4 / CH3CN = 70 / 30, 50 mmol/L KH2PO4 / CH3OH = 20 / 80 respectively. The compounds were certainly separated under water/acetonitrile system, or water/methanol system. With all compounds, good separation with good peak shape are reached (Figures 3, 4, 5). In addition, Miura and colleagues (1) reported that Chiral CD-Ph was applied in the separation of a second-generation antihistamine fexofenadine. The chiral separation of fexofenadine is carried out by using a plasma sample of 400 μL after treated by solid-phase extraction, which suggest that Chiral CD-Ph is also useful in clinical samples.
Figure 4: Chiral separation of Atropine.
In the durability test under reversed phase mode, propranolol was used as a sample to perform 1-month continuous running under the mobile phase of 50 mmol/L KH2PO4 / CH3CN = 70/30, the column pressure and peak shapes were evaluated as indicators of durability. There was no change observed in column pressures and peak shapes between the test start and the end after 1-month of the test, which suggests that Chiral CD-Ph is a durable column (Figure 6).
Figure 5: Chiral separation of Norfenefrine.
Chiral CD-Ph is packing material for chiral separation created from a precisely classified high-purity spherical silica with phenyl-carbamated β-cyclodextrin chemically bonded as a chiral selector. It is capable of applying under normal phase as well as reversed-phase mode, and excels at the chiral separation of basic and neutral compounds. Chiral CD-Ph column is recommended as an easy solution for chiral separation with the excellent selectivity as well as durability.
Figure 6: Durability test of Chiral CD-Ph in reversed-phase condition.
(1) M. Miura, T. Uno, T. Tateishi, and T. Suzuki, J. Pharm. Biomed. Ana.43, 741–745 (2007).