Single-isomer cyclodextrin Dotaz Zobrazit nápovědu
In this work, the synthesis, characterization, and chiral capillary electrophoretic study of heptakis-(2,3-di-O-methyl-6-O-carboxymethyl)-β-CD (HDMCM), a single-isomer carboxymethylated CD, are presented. The pH-dependent and selector concentration-dependent enantiorecognition properties of HDMCM were investigated and discussed herein. The enantioseparation was assessed applying a structurally diverse set of noncharged, basic, and zwitterionic racemates. The increase in the selector concentration and gross negative charge of HDMCM improved the enantioseparation that could be observed in the majority of the cases. HDMCM was also successfully applied as BGE additive in NACE using a methanol-based system in order to prove the separation selectivity features and to highlight the broad applicability of HDMCM. Over 25 racemates showed partial or baseline separation with HDMCM under the conditions investigated, among which optimal enantiomer migration order was found for the four stereoisomers of tadalafil, tapentadol, and dapoxetine, offering the possibility of a chiral CE method development for chiral purity profiling of these drugs.
- Klíčová slova
- Cyclodextrin, Enantiomer migration order, Enantioseparation, Nonaqueous capillary electrophoresis, Single isomer,
- MeSH
- beta-cyklodextriny chemie MeSH
- elektroforéza kapilární přístrojové vybavení metody MeSH
- koncentrace vodíkových iontů MeSH
- léčivé přípravky analýza chemie izolace a purifikace MeSH
- methanol chemie MeSH
- stereoizomerie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- beta-cyklodextriny MeSH
- carboxymethyl-beta-cyclodextrin MeSH Prohlížeč
- léčivé přípravky MeSH
- methanol MeSH
Herein we report on the synthesis, characterization and the novel capillary electrophoretic use of octakis-(2,3-di-O-methyl-6-O-carboxymethyl)-γ-cyclodextrin sodium salt (ODMCM). ODMCM is the first single-isomer carboxymethyl-γ-cyclodextrin that is fully methylated on its secondary side and carries ionizable carboxymethyl functions on its primary side. ODMCM was prepared with high isomeric purity through a four-step synthetic procedure. The purity of each intermediate was characterized by appropriate chromatographic methods, while the isomeric purity of the carboxymethylated product was determined by an HPLC method using a CD-Screen-IEC column and by a capillary electrophoretic method using indirect UV detection, as well. The structural identification of the ODMCM was carried out by 1D, 2D NMR spectroscopy and ESI-MS. The acid-base characterization of the chiral selector was carried out by 1H NMR-pH titration. The chiral separation ability of the synthesized selector was studied by chiral capillary electrophoresis. ODMCM was used as a background electrolyte additive to separate enantiomers of representative pharmacologically significant model molecules such as propranolol, citalopram, ketamine, tapentadol and dapoxetine. The effects of the selector concentration and the pH of the background electrolyte on the enantiorecognition properties were investigated. 1H NMR spectroscopy was further applied to get deeper insight of the host-guest inclusion complex formation. The pH-dependent enantioselectivity of this new single-isomer chiral selector was demonstrated by chiral capillary electrophoresis and 1H NMR spectroscopy.
- Klíčová slova
- (1)H NMR, Chiral capillary electrophoresis, Cyclodextrin synthesis, Enantioseparation, Host-guest interaction, Single-isomer,
- MeSH
- elektroforéza kapilární * MeSH
- gama-cyklodextriny chemie MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací * MeSH
- indikátory a reagencie MeSH
- koncentrace vodíkových iontů MeSH
- magnetická rezonanční spektroskopie MeSH
- spektrofotometrie ultrafialová * MeSH
- stereoizomerie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- carboxymethyl-gamma-cyclodextrin MeSH Prohlížeč
- gama-cyklodextriny MeSH
- indikátory a reagencie MeSH
The enantioselectivity of neutral single-isomer synthetic precursors of sulfated-β-cyclodextrins was studied. Four neutral single-isomer cyclodextrins substituted on the secondary side with acetyl and/or methyl functional groups, heptakis(2-O-methyl-3,6-dihydroxy)-β-cyclodextrin (HM-β-CD), heptakis(2,3-di-O-acetyl-6-hydroxy)-β-cyclodextrin (HDA-β-CD), heptakis(2,3-di-O-methyl-6-hydroxy)-β-cyclodextrin (HDM-β-CD), heptakis(2-O-methyl-3-O-acetyl-6-hydroxy)-β-cyclodextrin (HMA-β-CD), and their sulfated analogs the negatively charged heptakis(2,3-di-O-methyl-6-sulfato)-β-cyclodextrin (HDMS-β-CD) and heptakis(2,3-di-O-acetyl-6-sulfato)-β-cyclodextrin (HDAS-β-CD) were investigated by non-aqueous capillary electrophoresis in the view of enantiodiscrimination for various drugs and related pharmaceutical compounds. The focus of the present work was on the chiral selectivity studies of the neutral derivatives, which are the synthesis intermediates of the sulfated products. The chiral recognition experiments proved that among the neutral compounds the HMA-β-CD shows remarkable enantioselectivity towards chiral guests in non-aqueous capillary electrophoresis, while HM-β-CD, HDA-β-CD and HDM-β-CD failed to resolve any of the 25 studied racemates under the applied experimental conditions. In order to get deeper insight into the molecular interactions between the studied single-isomer cyclodextrin and chiral fluoroquinolones (ofloxacin, gatifloxacin and lomefloxacin) and β-blockers (propranolol), 1H and ROESY NMR experiments were performed. The 2-O-methylation in combination with the 3-O-acetylation of the host was evidenced to exclusively carry the essential spatial arrangement for chiral recognition.
- Klíčová slova
- (1)H NMR, Enantioseparation, Host-guest interaction, Non-aqueous chiral capillary electrophoresis, ROESY NMR, Single-isomer cyclodextrin,
- MeSH
- acetylace MeSH
- beta-cyklodextriny chemická syntéza MeSH
- elektroforéza kapilární * MeSH
- fluorochinolony chemie MeSH
- indikátory a reagencie MeSH
- magnetická rezonanční spektroskopie MeSH
- propranolol chemie MeSH
- stereoizomerie MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Názvy látek
- beta-cyklodextriny MeSH
- betadex MeSH Prohlížeč
- fluorochinolony MeSH
- heptakis(2,3-diacetyl-6-sulfo)-cyclodextrin MeSH Prohlížeč
- heptakis(2,3-dimethyl-6-sulfato)cyclodextrin MeSH Prohlížeč
- indikátory a reagencie MeSH
- propranolol MeSH
This contribution reports the synthesis, characterization and capillary electrophoretic application of heptakis-(6-O-sulfobutyl-ether)-β-cyclodextrin sodium salt, (6-(SB)7-β-CD). The compound was obtained through a five-steps synthesis and it represents the first example of single-isomer sulfobutylated cyclodextrin that carries the negatively charged functions exclusively on its primary side and it is unmodified on the lower rim. The purity of each intermediate was determined by appropriate liquid chromatographic methods, while the isomeric purity of the final product was established by an ad-hoc developed HPLC method based on a CD-Screen-IEC column. The structural identification of 6-(SB)7-β-CD was carried out by 1D, 2D NMR spectroscopy and ESI-MS. The chiral separation ability of 6-(SB)7-β-CD was studied by chiral capillary electrophoresis using the single-isomer host as a background electrolyte additive to separate the enantiomers of a representative set of pharmacologically significant model compounds such as verapamil, dapoxetine, ondansetron, propranolol, atenolol, metoprolol, carvedilol, terbutaline, amlodipine and tadalafil. The enantiomer migration order and the effects of the selector concentration on the enantiorecognition properties were investigated. NMR spectroscopy was applied to deepen and further confirm the host-guest interactions and in the case of the model compound dapoxetine a potential representation for the supramolecular assembly was developed based on the dataset collected by the extensive 2D NMR analysis. This single-isomer chiral selector offers a new alternative to the widely applied randomly sulfobutylated- and sulfated-beta-cylodextrins as well as to the single-isomer sulfated and carboxymethylated derivatives in chiral separations.
- Klíčová slova
- (1)H NMR, Chiral capillary electrophoresis, Cyclodextrin synthesis, Enantioseparation, Host-guest interaction, Single-isomer,
- MeSH
- beta-cyklodextriny analýza chemická syntéza chemie MeSH
- elektroforéza kapilární metody MeSH
- elektrolyty MeSH
- hmotnostní spektrometrie s elektrosprejovou ionizací MeSH
- koncentrace vodíkových iontů MeSH
- magnetická rezonanční spektroskopie MeSH
- stereoizomerie MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- beta-cyklodextriny MeSH
- elektrolyty MeSH
- SBE7-beta-cyclodextrin MeSH Prohlížeč
The present study describes a rapid and effective capillary electrophoresis (CE) method for the enantioseparation of pindolol using single-isomer octa(6-O-sulfo)-γ-cyclodextrin. The complexation parameters were determined under neutral and high pH conditions to identify optimal separation conditions using a theoretical model. Baseline separation of pindolol enantiomers was achieved within 6 min in a sodium/MOPS buffer, pH 7.2, with a selector concentration of 6 mM. The method was validated according to the ICH guidelines using imidazole as an internal standard. Low limits of detection and quantification were found, specifically 1.2 μg/mL and 4 μg/mL (0.6 μg/mL and 2 μg/mL per enantiomer), respectively. The calibration curves showed good linearity, with a coefficient of determination R2 ≥ 0.999 over a 5 - 55 μg/mL concentration range and over a 50 - 300 μg/mL concentration range of the racemic mixture. The relative standard deviations (%RSD) of intra-day and inter-day precision were lower than 8% at LOQ level, lower than 3% at 50 μg/mL level and lower than 1.5% at 300 μg/mL level. Accuracy ranged from 95 to 103% (106% at LOQ level). The proposed method was successfully tested on a medical formulation of Visken® Sandoz intravenous solution and Visken® Teofarma pills for oral use.
- Klíčová slova
- Capillary electrophoresis, Enantioseparation, Method validation, Pindolol, Single-isomer cyclodextrin, β-blockers,
- MeSH
- časové faktory MeSH
- elektroforéza kapilární metody MeSH
- gama-cyklodextriny chemie MeSH
- kalibrace MeSH
- koncentrace vodíkových iontů MeSH
- limita detekce MeSH
- pindolol izolace a purifikace MeSH
- pufry MeSH
- reprodukovatelnost výsledků MeSH
- software * MeSH
- stereoizomerie MeSH
- Publikační typ
- časopisecké články MeSH
- validační studie MeSH
- Názvy látek
- gama-cyklodextriny MeSH
- gamma-cyclodextrin MeSH Prohlížeč
- pindolol MeSH
- pufry MeSH
The synthesis of batch-to-batch reproducible cyclodextrin (CD) derivatives often requires functionalization at specific positions of the CD skeleton. However, the regioselective preparation of this type of CD derivatives remains a challenge in synthetic chemistry. Thus, the present study aimed to prepare all positional regioisomers on the primary rim of homobifunctionalized diazido-α-CDs by selective substitution on the primary rim. Specifically, three positional regioisomers 6A,6B-, 6A,6C-, and 6A,6D-diazido-α-CDs were prepared via different intermediates (using sulfonylation with capping agents, bromination and tosylation). Furthermore, heterobifunctionalized 6A-azido-6X-mesitylenesulfonyl-α-CDs were also synthesized, and all regioisomers were successfully separated by HPLC. Moreover, the heterobifunctionalized α-CD regioisomers were isolated in gram-scale quantities, isomers AB and AC in the form of a pseudoenantiomeric mixture. The pseudoenantiomers AC/CA and AB/BA were resolved on an analytical scale by HPLC-MS at 10 °C. Thus, the presented synthetic and analytical methods for homo- and heterodisubstituted α-CDs are efficient and reproducible for the preparation of various pure regioisomeric CD derivatives. Accordingly, our findings indicate, (i) the versatility of selectively modified azido and mesitylene CD skeletons in preparing new types of α-CD derivatives and (ii) the potential of using resolved α-CD pseudoenantiomers in other research fields such as organocatalysis.
- Klíčová slova
- diazido-alpha-cyclodextrin, heterobifunctionalized alpha-cyclodextrin, homobifunctionalized alpha-cyclodextrin, regioisomers, regioselectivity,
- Publikační typ
- časopisecké články MeSH
In this study, the apparent binding constants and limiting mobilities of the multiply charged complexes of the Δ- and Λ-enantiomers of Ru(II)- and Fe(II)-polypyridyl associates ([Ru(2,2'-bipyridine)3 ]2+ , [Ru(1,10-phenanthroline)3 ]2+ , and [Fe(1,10-phenanthroline)3 ]2+ ) with single-isomer 2,3-diacetylated-6-sulfated-cyclodextrins (CDs) (12Ac-6S-α-CD, 14Ac-7S-β-CD, and 16Ac-8S-γ-CD) were determined by ACE using uncorrected and ionic strength corrected actual mobilities of the species involved. Two limiting models were tested for the ionic strength correction of the actual mobilities based on an empirical relation for the ionic strength correction of multivalent ionic species. In model 1, the nominal values of the charge numbers (zS,nom ) and analytical concentrations (cS,nom ) of the above CD selectors in the BGEs were applied for calculation of the BGE ionic strength, as usual. In model 2, the CD selectors were considered as singly charged species (zS = -1) with |zS,nom |-times higher concentrations in the BGE than their analytical concentrations (cS = |zS,nom | × cS,nom ) in the calculation of the BGE ionic strength. In all three cases-with uncorrected actual mobilities as well as with actual mobilities corrected according to the two limiting models-the measured effective mobilities of the above enantiomers fit well the theoretical curves of their mobility dependences on the CD selectors concentrations in the BGE, with high average coefficients of determination (R2 = 0.9890-0.9995). Nevertheless, the best physico-chemically meaningful values of the apparent binding constants and the limiting mobilities of the enantiomer-CDs complexes with low RSDs were obtained using the actual mobilities of the species involved corrected according to model 2.
- Klíčová slova
- Affinity capillary electrophoresis, Binding constant, Cyclodextrins, Electrophoretic mobility, Ionic strength,
- MeSH
- cyklodextriny chemie MeSH
- elektroforéza kapilární metody MeSH
- molekulární modely MeSH
- osmolární koncentrace MeSH
- sírany chemie MeSH
- stereoizomerie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cyklodextriny MeSH
- sírany MeSH
Sulfated cyclodextrins (CDs) are multiply negatively charged molecules widely used as chiral selectors in capillary electrophoresis (CE). In some of their applications, the effective charge numbers of their molecules were observed to be lower than the numbers of the attached sulfated groups due to strong binding of counterions. However, degree of reduction of the theoretical charge was not quantified. For that reason, in this study, capillary isotachophoresis (CITP) and capillary zone electrophoresis (CZE) were applied for the determination of the effective charge numbers and actual ionic mobilities of two kinds of sulfated CDs: single isomer sulfated α-, β-, and γ-CDs (SI-CDs) and randomly highly sulfated α-, β-, and γ-CDs (HS-CDs). The effective charge numbers of the SI-CDs and HS-CDs were determined from the length of their ITP zones, the ionic mobilities determined by CZE, and molar concentrations of their solutions applied for CITP analysis, and from the same parameters of reference compounds, formic acid for SI-CDs and dichloroacetic acid for HS-CDs. The determined effective charge numbers of the SI-CDs were equal to or only slightly lower than the numbers of sulfate groups in their molecules but the effective charge numbers of randomly HS-CDs were significantly (22.2%-27.8%) reduced as compared to the average numbers of sulfate groups in their molecules. In accordance with a lower number of sulfate groups in SI-CDs than in HS-CDs, the absolute values of the actual ionic mobilities of SI-CDs (35.5-37.5) × 10-9 m2 V-1 s-1 were lower than those of HS-CDs (43.5-44.1) × 10-9 m2 V-1 s-1.
- Klíčová slova
- capillary isotachophoresis, capillary zone electrophoresis, charge number, counterion condensation, effective charge,
- Publikační typ
- časopisecké články MeSH
CE using randomly highly sulfated α-, β-, and γ-CDs (S-α-CD, S-β-CD, S-γ-CD), sulfobutylether-β-CD (SBE-β-CD), single isomer (6-O-sulfo) α-, β-, and γ-CDs, and their derivatives as stereoselectors was applied to chiral analysis of polypyridyl complexes of [Ru(bpy)3 ]2+ , [Ru(phen)3 ]2+ , and [Fe(phen)3 ]2+ (bpy = 2,2'-bipyridine; phen = 1,10 phenanthroline). The best separations of Δ- and Λ-enantiomers of the these complexes with high resolution (up to R1,2 = 7.0) and short analysis times (10-20 min) were achieved in the BGE composed of 22 mM NaOH/35 mM H3 PO4 , pH 2.4, containing 1.5-6.0 mM S-α-CD or S-β-CD, or SBE-β-CD as chiral selectors. The developed method was applied to the assessment of enantiomeric purity of several samples of [Ru(bpy)3 ]2+ catalyst. CE experiments were performed in a homemade analyzer equipped with bare or hydroxypropylcellulose-coated fused-silica capillaries (total/effective length 40/29 cm, id/od 50/375 μm) and an UV absorption detector operating at 206 nm. In addition to chiral analysis, apparent binding constants of the complexes of [Ru(bpy)3 ]2+ , [Ru(phen)3 ]2+ , and [Fe(phen)3 ]2+ enantiomers with five sulfated CDs (S-α-CD, S-β-CD, S-γ-CD, SBE-β-CD, and 16Me-8S-γ-CD) were determined from the dependence of their effective electrophoretic mobilities on the concentration of the CDs in the BGE by nonlinear regression analysis. Calculated apparent binding constants of these complexes were found to be in the (1.10-4.66) × 103 L/mol range. Moreover, it was shown that at selected concentrations of some S-CDs and suppressed or very low electroosmotic flow, the exceptional enantioseparations with infinite resolution could be achieved.
- Klíčová slova
- Binding constant, Capillary electrophoresis, Chiral separation, Polypyridyl Fe(II) complex, Polypyridyl Ru(II) complex,
- MeSH
- cyklodextriny chemie MeSH
- elektroforéza kapilární metody MeSH
- nelineární dynamika MeSH
- pyridiny analýza chemie MeSH
- ruthenium analýza chemie MeSH
- sírany chemie MeSH
- stereoizomerie MeSH
- železnaté sloučeniny analýza chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cyklodextriny MeSH
- pyridiny MeSH
- ruthenium MeSH
- sírany MeSH
- železnaté sloučeniny MeSH
It has been reported many times that the commercial mixtures of chiral selectors (CS), namely highly sulfated beta-CDs (HS-beta-CDs), provide remarkable enantioselectivity in CZE when compared with single-isomer CDs, even single-isomer HS-beta-CDs. This enhanced enantioselectivity of multi-CS enantioseparative CZE is discussed in the light of multi-CS model that we have introduced earlier. It is proposed on a theoretical basis and verified experimentally that the two enantiomers of a chiral analyte under interaction with a mixture of CSs are very likely to differ in their limit mobilities, which is opposite to single-CS systems where the two limit mobilities are likely to be the same. Thus while the enantioseparation is usually controlled by different distribution constants between the two enantiomers and CS used in single-CS systems, an additional, electrophoretic, enantioselective mechanism resulting from different limit mobilities may play a significant role in multi-CS systems. This additional mechanism generally makes the multi-CS systems more selective than the single-CS systems. The possible inequality of limit mobilities is also significant for optimization of separation conditions using mixtures of CSs. A practical example supporting our considerations is shown on enantioseparation of lorazepam in the presence of a commercial mixture of HS-beta-CDs and a single-isomer HS-beta-CD, heptakis(6-O-sulfo)-beta-CD.
