Vancomycin chiral selectors

Bhushan and Parsad [65] resolved dansyl amino acids on erythromycin impregnated thin-layer chromatographic (TLC) silica plates. The mobile phase used was different ratios of 0.5 M aqueous NaCl-acetonitrile-methanol. Further, Bhushan and Thiong o [66] achieved the chiral resolution of dansyl amino acids on silica TLC plates impregnated with vancomycin chiral selector. The mobile phase used for this study was acetonitrile-0.5 M aqueous NaCl (10 4 and 14 3, v/v). The chiral recognition mechanisms of antibiotic CSPs in sub-SFC, SFC, CEC, and TLC modes of chromatography were found to be similar to HPLC. 

Table 2 lists a selected set of the considerable data published on the separation of native or derivatized amino acids on macrocyclic glycopeptide CSPs [1, 2, 11-14], The vancomycin chiral selector was found to have a lower efficacy in the separation of amino acids compared to that of the three other commercialized CSP (Chirobiotic T, TAG, and R) [14]. 

Avery recent study [128] deals with the comparison of two commercially available vancomycin-based CSPs with different surface coverage of the chiral selector in the enantioseparation of P-blockers and profens, by RP and POM separation modes. Higher retention and better resolution were obtained on the CSP with higher coverage of vancomycin in both the separation modes. However, in the case of pro fens, higher retention was not always accompanied by an improvement of the enantioselectivity in the RP mode. An accurate study of the influence of the mobile phase composition was also performed in both the separation modes. 

Cyclic amines (including local anesthetic drugs) and amides were among the first classes of chiral compounds investigated in the early stages of the application of macrocyclic antibiotics as chiral selectors therefore, they were screened on vancomycin [7], teicoplanin [30], and ristocetin A [33] CSPs, under RPmode systems. Cyclic imides (including barbiturates, piperidine-2,6-diones, and mephenytoin) have been separated on a vancomycin CSP [157], under NP and RP mobile phase conditions. 

The [ -adrenoreceptors antagonists (also called [)-blockers) comprise a group of chiral drugs that are mostly used in the treatment of cardiovascular disorders such as hypertension, cardiac arrhythmia, or ischemic heart disease. Teicoplanin is the chiral selector most exploited for the enantioseparation of this class of compounds, followed by vancomycin. Several P-blockers have been analyzed, particularly in the... 

Bosakova, Z., Cufinovd, E., and Tes ovd, E., Comparison of vancomycin-based stationary phases with different chiral selector coverage for enantioselective separation of selected drugs in high-performance liquid chromatography, J. Chromatogr. A, 1088, 94, 2005. 

Sun, Q. and Olesik, S.V., Chiral separation by simultaneous use of vancomycin as stationary phase chiral selector and chiral mobile phase additive, J. Chromatogr. B, 745, 159, 2000. 

Armstrong et al. ° first introduced chiral stationary phases based on macrocyclic antibiotics. Vancomycin, ristocetin A, teicoplanin, avoparcin, rifamycin B and thiostrepton are used as chiral selectors. They posses a broad enantiorecognition range, similar to protein based CSPs. However, CSPs based on macrocyclic antibiotics show higher stability and capacities.Underivatized amino acids, N-derivatized amino-acids, acidic compounds, neutrals, amides, esters and amines can be separated.The first four of the above-mentioned chiral selectors appear to have the largest enantiorecognition range.The selectors can also be derivatized to obtain different enantioselectivities. 

Vancomycin was one of the most employed chiral selectors for separating acidic compounds. Introduced by Armstrong et al. for the separation of a wide range of compounds, vancomycin is a glycopeptide antibiotic that contains numerous... 

Brush-type, proteins, CDs, natural molecular imprint-based polymers (MIP), and macrocyclic antibiotics have been immobilized as chiral selectors on packed-CEC columns. Zheng and Shamsi demonstrated the possibility of using chiral CEC—ESI/MS with a commercially packed column for the determination of warfarin enantiomers in human plasma using coumachlor as an internal standard (IS). Robustness of this chiral CEC capillary was recently improved by a novel procedure and applied for the simultaneous enantiosepara-tion of height /1-blockers with multimodal CSP using different combinations of vancomycin and teicoplanin, as presented in Figure 5. ... 

Eanali, S., Desiderio, C., Schulte, G., Heitmeier, S., Strickmann, D., Chankvetadze, B., and Blaschke, G. (1998). Chiral capillary electrophoresis-electrospray mass spectrometry coupling using vancomycin as chiral selector. /. Chromatogr. A 800, 69—76. 

The use of macrocyclic antibiotics as chiral selectors for HPLC was first proposed by Armstrong et al. [50] in 1994. The most successful of the CSPs are based on the glycopeptide antibiotics vancomycin, teicoplanin and ristocetin A and are commercially available through Advanced Separation Technologies Inc. (Astec Inc.) as Chirobiotic V , Chirobiotic 1 and Chirobiotic R , respectively. More recently, a number of other derivatives of these antibiotics have also been developed offering different stereoselectivities. A comprehensive handbook is now available from Astec Inc. [51 ] alongside a number of recent review articles... 

The application of antibiotics as chiral selectors has resulted in the successful resolution of almost all types of neutral, acidic, and basic racemic molecule. These antibiotics have been used for the enantiomeric resolution of amino acids, their derivatives, peptides, alcohols, and other pharmaceuticals. The selectivities of the most commonly used antibiotic-based (vancomycin, teicoplanin, and ristocetin A) CSPs varied from one racemate to another and are given in Table 1. Vancomycin was used for the chiral resolution of amino acids, amines, amides, imides, cyclic amines, amino alcohols, hydantoins, barbiturates, oxazolidinones, acids, profens, and other pharmaceuticals. Teicoplanin was found to be excellent chiral selector for the enantiomeric resolution of amino acids, amino alcohols, imides, peptides, hydantoins, a-hydroxy and halo acids, and oxazolidinones, whereas ristocetin A is capable of chiral resolution of amino acids, imides, amino... 

In addition to the common use of vancomycin and teicoplanin, the use of other antibiotics as chiral selectors in HPLC were limited. Only a few reports are available in the literature dealing with these antibiotics as HPLC CSPs. Armstrong et al. [42] resolved about 230 racemates on the ristocetin A antibiotic covalently bonded to silica gel. The resolution was carried out using the three modes of mobile phases. The results were complimentary to those obtained on vancomycin and teicoplanin CSPs. In another study, the effect of selector coverage and mobile phase composition on enantiomeric resolution with ristocetin A CSP was carried out by Armstrong et al. [43]. Thiostrepton-based CSP was also used to resolve the enantiomers of thioridazine, 2,2,2-trifluoro-l-... 

An EPME based on carbon paste impregnated with macrocyclic antibiotic vancomycin as chiral selector was proposed for the enantioanal-ysis of S-perindopril raw material and from its pharmaceutical formulation [49]. The proposed electrode was applied for the assay of... 

EPMEs based on antibiotics are proposed for the enantioanalysis of L-vesamicol [51]. A carbon paste was modified with antibiotics (vancomycin, teicoplanin and teicoplanin modified with acetonitrile), as chiral selectors. The EPMEs based on antibiotics were reliably used for enantiopurity tests of L-vesamicol using the direct potentiometric technique. The following linear concentration ranges 1.0 x 10-6 - 1.0 x 10 4,... 

The macrocyclic antibiotics vancomycin [51,52] and teicoplanin [53] were successfully employed as chiral selectors for enantiomer separation in p-CEC. Warfarin,... 

There are literally hundreds of glycopeptide antibiotics, from which vancomycin, teicoplanin, and subsequently risuxretin A (for structures see Fig. 9.18) have been commercialized by Astec as Chirobiotic V, ChiiX)biotic T. and Chirobiotic R. More recently, avoparcin (see Fig. 9.18) has also been successfully applied as a chiral selector [280],... 

The Chirobiotic series of colrrmns (T based on teicoplarrin and V on vancomycin as immobilized chiral selector) can be used with polar-organic mobile phase of over 90% methanol and a small amount of aqueous acid or salt solution. 

Desiderio, C. Polcaro, C.M. Padiglioni, P. Fanali, S. Enantiomeric separation of acidic herbicides by capillary electrophoresis using vancomycin as chiral selector. J. Chromatogr., A 1997, 781, 503-513. 

Tesarova and Bosakova [58] proposed an HPLC method for the enantio-selective separation of some phenothiazine and benzodiazepine derivatives on six different chiral stationary phases (CSPs). These selected CSPs, with respect to the structure of the separated compounds, were either based on b-CD chiral selectors (underivatized (J>-CD and hydroxypropyl ether (3-CD) or on macrocyclic antibiotics (vancomycin, teicoplanin, teicoplanin aglycon and ristocetin A). Measurements were carried out in a reversed-phase separation mode. The influence of mobile phase composition on retention and enantio-selective separation was studied. Enantioselective separation of phenothiazine derivatives, including levopromazine (LPZ), promethazine and thioridazine, was relatively difficult to achieve, but it was at least partly successful with both types of CSPs used in this work (CD-based and glycopeptide-based CSP), except for levomepromazine for which only the [CCD-based CSP was suitable. 

For the separation of anionic analytes, the positively charged macrocyclic antibiotic vancomycin is one of the most commonly used chiral selectors. It was introduced by Armstrong and coworkers as a new class of chiral selector in CE, HPLC and thin-layer chromatography for the separation of a wide range of enantiomers [29, 47-52]. It contains multiple stereogenic centers and a variety of functional groups. 

To date, the capability of macromolecular peptides as molecular recognition sites has been poorly characterized. Due to the analytical techniques available, first investigations on host-guest complexes were done in the homogeneous phase [55]. One of the most popular cyclic compounds is the depsipeptide, valinomycin, which can complex potassium ions selectively and carry them through lipid membranes [56], Another interesting receptor is the peptide antibiotic, vancomycin [57], This consists of a complicated tricyclic pep-tidic structure and can be used as chiral selector [58] in capillary electrophoresis and HPLC. 

Glycopeptide antibiotics have been found to be very effective chiral selectors in the enantiomeric separation of racemic pharmaceutical compounds. Vancomycin, ristocetin A, rifamycins, teicoplanin, kanamycin, streptomycin, and avoparcin have been added to the running buffer to obtain enantioseparation (161,203— 207). A few technical modifications, such as coated capillaries and separation conditions in the reverse polarity mode (as opposed to normal polarity mode, where the flow is from anode to cathode) were found to improve sensitivity and increase efficiency (116,208). 

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