1
|
Reddy GNM, Huqi A, Iuga D, Sakurai S, Marsh A, Davis JT, Masiero S, Brown SP. Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State. Chemistry 2016; 23:2315-2322. [PMID: 27897351 PMCID: PMC5396329 DOI: 10.1002/chem.201604832] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Indexed: 11/24/2022]
Abstract
The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G‐quartet‐based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion‐ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G‐quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon‐like assemblies as revealed by fast magic‐angle spinning (MAS) NMR spectroscopy. Distinct N−H⋅⋅⋅N and N−H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon‐like self‐assembly resulting in markedly different 2D 1H solid‐state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible–further demonstrating the changes that occur in the self‐assembly process of a lipophilic nucleoside upon a solid‐state to solution‐state transition and vice versa. A systematic study for complexation with different cations (K+, Sr2+) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid‐state structure may not reflect the stability of the same supramolecular entity in another phase.
Collapse
Affiliation(s)
- G N Manjunatha Reddy
- Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK
| | - Aida Huqi
- Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum, Università di Bologna, 40126, Bologna, Italy
| | - Dinu Iuga
- Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK
| | - Satoshi Sakurai
- JEOL (UK), Silver Court, Watchmead, Welwyn Garden City, AL7 1LT, UK
| | - Andrew Marsh
- Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK
| | - Jeffery T Davis
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA
| | - Stefano Masiero
- Dipartimento di Chimica "Giacomo Ciamician", Alma Mater Studiorum, Università di Bologna, 40126, Bologna, Italy
| | - Steven P Brown
- Department of Physics and Department of Chemistry, University of, Warwick, Coventry, CV4 7AL, UK
| |
Collapse
|
2
|
Przybylski P, Pyta K, Klich K, Schilf W, Kamieński B. 13C and 15N CP/MAS, 1H-15N SCT CP/MAS and FTIR spectroscopy as tools for qualitative detection of the presence of zwitterionic and non-ionic forms of ansa-macrolide 3-formylrifamycin SV and its derivatives in solid state. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2014; 52:10-21. [PMID: 24347399 DOI: 10.1002/mrc.4028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 06/03/2023]
Abstract
(13)C, (15)N CP/MAS, including (1)H-(13)C and (1)H-(15)N short contact time CP/MAS experiments, and FTIR methods were applied for detailed structural characterization of ansa-macrolides as 3-formylrifamycin SV (1) and its derivatives (2-6) in crystal and in powder forms. Although HPLC chromatograms for 2/CH3 OH and 2/CH3 CCl3 were the same for rifampicin crystals dissolved in respective solvents, the UV-vis data recorded for them were different in 300-375 nm region. Detailed solid state (13)C and (15)N CP/MAS NMR and FTIR studies revealed that rifampicin (2), in contrast to 3-formylrifamycin SV (1) and its amino derivatives (3-6), can occur in pure non-ionic or zwitterionic forms in crystal and in pure these forms or a mixture of them in a powder. Multinuclear CP/MAS and FTIR studies demonstrated also that 3-6 derivatives were present exclusively in pure zwitterionic forms, both in powder and in crystal. On the basis of the solid state NMR and FTIR studies, two conformers of 3-formylrifamycin SV were detected in powder form due to the different orientations of carbonyl group of amide moiety. The PM6 molecular modeling at the semi-empirical level of theory, allowed visualization the most energetically favorable non-ionic and zwitterionic forms of 1-6 antibiotics, strongly stabilized via intramolecular H-bonds. FTIR studies indicated that the originally adopted forms of these type antibiotics in crystal or in powder are stable in standard laboratory conditions in time. The results presented point to the fact that because of a possible presence of two forms of rifampicin (compound 2), quantification of the content of this antibiotic in relevant pharmaceuticals needs caution.
Collapse
Affiliation(s)
- Piotr Przybylski
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614, Poznan, Poland
| | | | | | | | | |
Collapse
|