Teicoplanins

Twenty-eight chiral compounds were separated from their enantiomers by HPLC on a teicoplanin chiral stationary phase. Figure 8-12 shows some of the structures contained in the data set. This is a very complex stationary phase and modeling of the possible interactions with the analytes is impracticable. In such a situation, learning from known examples seemed more appropriate, and the chirality code looked quite appealing for representing such data. 

Figure 8-12. Examples of las eluted enantiomers In a chromatographic separation on chiral HPLC with teicoplanin stationary-phase.

The chirobiotic chiral stationary phases (103,104) are based on macrocycHc antibiotics such as vancomycin (4) and teicoplanin (5). 

Other specific discovery assays have been used such as differential inhibition of a vancomycin resistant S. aureus strain and its susceptible parent, and an assay based on antagonism of the antibacterial activity by N,A/-diacetyl-L-Lys-D-Ala-D-Ala [24570-39-6] a tripeptide analogue of the dalbaheptides receptor. AppHcation of this latter test to 1936 cultures (90) led to the isolation of 42 dalbaheptides, six of which, including kibdelin (Table 3), parvodicin (Table 3), and actinoidin A2 (68) were novel. A colorimetric assay based on competition between horseradish peroxidase bound teicoplanin and the... 

Recovery and Purification. The dalbaheptides are present in both the fermentation broth and the mycelial mass, from which they can be extracted with acetone or methanol, or by raising the pH of the harvested material, eg, to a pH of 10.5—11 for A47934 (16) (44) and A41030 (41) and actaplanin (Table 2) (28). A detailed review on the isolation of dalbaheptides has been written (14). Recovery from aqueous solution is made by ion pair (avoparcin) or butanol (teicoplanin) extraction. The described isolation schemes use ion-exchange matrices such as Dowex and Amberlite IR, acidic alumina, cross-linked polymeric adsorbents such as Diaion HP and Amberlite XAD, cation-exchange dextran gel (Sephadex), and polyamides in various sequences. Reverse-phase hplc, ion-exchange, or affinity resins may be used for further purification (14,89). 

Fig. 1. Stereostmeture of teicoplanin aglycone [89139-42-4] obtained from a Dreiding model (83) where is hydrogen, is nitrogen, O is carbon, is...

In Vitro Properties. The antibacterial spectmm of most dalbaheptides is known (Table 1). Vancomycin (39) and/or teicoplanin (Table 3) are generally introduced as reference compounds. Direct comparative data for some dalbaheptides tested under the same experimental conditions are given in... 

In the parvodicin and teicoplanin series (Table 3) the nature and length of the fatty acid portion of the glycoHpid moiety only slightly influence the activity in vitro. Dalbaheptides are bactericidal against actively growing, but not against resting, bacteria (33). 

In Vivo Properties. The efficacy of dalbaheptides has been assessed ia various models of experimental septicemia ia mice. In general there was good correlation between the ED qS (effective doses which prevent death ia 50% of test animals) and the MICs on test strains. Teicoplanin was very effective, ED q values ranged from 0.11 to 0.72 mg/kg sc administration for septicemias caused by S. pyogenes S. pneumoniae and S. aureu whereas for vancomycin ED qS were from 0.58 to 7.2 mg/kg (33). Eremomycin (52) had therapeutic activity 2—3 times greater than vancomycin. Therapeutic indices... 

This resistance, inducible by low concentrations of dalbaheptides, is plasmid mediated and is transferable. Concomitant with the induction of resistance is the appearance or increased expression of a protein having a molecular weight of either 39,500 or 39,000. The enzymatic activity of this material has been postulated (112). Although the mechanism of resistance induction by dalbaheptides is unknown, different dalhabaheptides have different induction capacity. Vancomycin (39) is the most powerful inducer teicoplanin is a very weak inducer. 

The -NH(CH2)3N(CH2)2 amide of teicoplanin factor A2-2, coded MPT. 62,873 [122173-74-4] was also prepared. The combined effect of a moderate basicity and a slightly increased lipophilicity at neutral pH probably led to a better penetration through the cell wall. MDL 62,873 was consistentiy more active than teicoplanin against CNS clinical isolates (119,120). No semisynthetic dalbaheptide is under clinical evaluation at this writing. 

Only three dalbaheptides are commercialized vancomycin (39) and teicoplanin (18—22) for human health, and avoparcin (63—65) for animal usage. Vancomycin, the main trademark of which is EH Lilly s Vancocin had 1990 sales around 160 million. Total annual production is in the vicinity of 8 t. Teicoplanin, trademarked Targocid, had 1990 sales of 35 million corresponding to 200 kg. Teicoplanin is commercialized in Europe, Hong Kong, Korea, and the Middle East. It is at the late developmental clinical phase in North America and Japan. Avoparcin is used as a growth promoting feed additive (see... 

Clinical Use. Vancomycin and teicoplanin as fomiulated dmgs are lyophilized powders to be reconstituted with sterile water for injection. Vancomycin hydrochloride [1404-93-9] is presented in vials of 500 mg that give 100—200 mL solution of pH 2.5—4.2. It is administered by slow (60 min) infusion at a dose of 500 mg every 6 h or 1 g every 12 h/d. The teicoplanin contains the five factors (87%) plus 13% of the pseudoaglycone T-A3-1. It is presented in vials containing 200 mg of lyophili ed power that after dissolution with 3 mL of solvent gives a solution at pH 7.5. The dose regimen is 200—800 mg/d by iv bolus adrninistration. 

Some ligand-exchange CSPs have been used at preparative level [31, 32]. In this case it must be taken into account that an extraction process, to remove the copper salts added to the mobile phase, must be performed following the chromatographic process [33]. Teicoplanin, in contrast, resolves all ordinary a and (3-amino acids with mobile phases consisting of alcohol/water mixtures. No buffer is needed in the... 

Vancomycin, ristocetin A and teicoplanin are produced as fermentation products of Streptomyces orientalis, Nocardia lurida and Actinoplanes teichomyceticus, respectively. All three of these related compounds consist of an aglycone basket made up of fused macrocyclic rings and pendant carbohydrate moieties (Fig. 2-1). The macrocycles contain both ether and peptide linkages. The aglycones of vancomycin and teicoplanin contain two chloro-substituted aromatic rings, while the analogous portion of ristocetin A contains no chloro substituents. 

Fig. 2-1 Proposed structures of three macrocycUc glycopeptides. On teicoplanin, R = 8-methyl-nonanoic acid.

Fig. 2-2. The enantiomeric sepai ation of P-blockers on teicoplanin CSP (250 x 4.6 mm) with the same mobile phase composition methanol with 0.1 % acetic acid and 0.1 % triethylamine (v/v). The flow rate was 1.0 mL min at ambient temperature (23 C).

When analytes lack the selectivity in the new polar organic mode or reversed-phase mode, typical normal phase (hexane with ethanol or isopropanol) can also be tested. Normally, 20 % ethanol will give a reasonable retention time for most analytes on vancomycin and teicoplanin, while 40 % ethanol is more appropriate for ristocetin A CSP. The hexane/alcohol composition is favored on many occasions (preparative scale, for example) and offers better selectivity for some less polar compounds. Those compounds with a carbonyl group in the a or (3 position to the chiral center have an excellent chance to be resolved in this mode. The simplified method development protocols are illustrated in Fig. 2-6. The optimization will be discussed in detail later in this chapter. 

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