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Fluorescent triazolyl spirooxazolidines: Synthesis and NMR stereochemical studies
摘要： Carbon-heteroatom chemistry is a method of choice for rapid construction of complex molecules. In the recent decade, its various applications flourished thanks to the Click chemistry approach. Herein, we use a combination of C-X formation reactions to complete the synthesis of 1,2,3-triazolyl spirooxazolidines, bearing the fluorenylmethoxycarbonyl (fmoc) substituent. Thanks to the application of 2D-NMR spectroscopic methods and a multilevel computational approach, including a medicinal chemistry – inspired conformational search, PM7 semiempirical and DFT-based geometry optimization finalized with DFT-GIAO NMR shielding constant calculation, we were able to investigate the conformational space and assign cis/trans configuration in complex NMR spectra. For the obtained fmoc derivatives we recorded UV-VIS absorption and emission spectra. The obtained compounds contain pharmacophoric groups characteristic for endocannabinoid system modulators- CB1 receptor ligands or FAAH inhibitors.
关键词： spirooxazolidine,oxazolidine,NMR,Triazole,stereochemistry
更新于2025-09-19 17:15:36
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Stereochemistry controlled supramolecular architectures of novel tetrahydroxy functionalized amphiphilic carbocyanine dye
摘要： The synthesis of novel amphiphilic 5,5',6,6'-tetrachlorobenzimidacarbocyanine (TBC) dye derivatives with amino-propanediol head groups differing in stereochemistry (chiral enantiomers, meso-form, and conformer) is reported. For the achiral meso-form, a new synthetic route towards asymmetric cyanine dyes was established. All compounds form J-aggregates in water whose optical properties were characterized by spectroscopic methods. The supramolecular structure of the aggregates was investigated by cryo-transmission electron microscopy (cryo-TEM), cryo-electron tomography (cryo-ET), and atomic force microscopy (AFM) revealing extended sheet-like aggregates for the chiral enantiomers and nanotubes for the mesomer, respectively, while the conformer forms predominately needle-like crystals. The experiments demonstrate that the aggregation behavior of compounds can be controlled solely by head group stereochemistry which in case of the enantiomers enables formation of extended hydrogen bond chains by the hydroxyl functionalities. In case of the achiral meso-form, however, such chains turned out to be sterically excluded.
关键词： Stereochemistry,cryo-TEM,supramolecular architectures,amphiphilic carbocyanine dye,cryo-ET,J-aggregates,AFM
更新于2025-09-19 17:13:59
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ECCD characterization of monotopically binding guests in host-guest complexes with a bis-(zinc porphyrin) tweezer
摘要： We have investigated the possibility to use a stiff-stilbene linked bisporphyrin tweezer with inherent helicity for Exciton-Coupled Circular Dichroism (ECCD) characterization of a series of monotopically binding amine guest molecules. CD signals were observed for a variety of monoamines at relatively low tweezer:amine (host:guest) ratios between 1:10 to 1:70. For the amines producing the most intense CD signals a binding stoichiometry of 1:2 was found. A likely explanation is the presence of guest-guest interactions in the complexes. This is supported by observing a correlation between CD signal intensity and magnitude of possible non-covalent binding between the guests, which we can divide into three groups showing no, moderate or strong response, respectively. Further support for this rationalization comes from molecular modelling.
关键词： absolute stereochemistry,molecular modelling,bis-porphyrin tweezers,monotopic binding,exciton-coupled circular dichroism
更新于2025-09-09 09:28:46