75172-31-5Relevant articles and documents
Electrostatics Favor PNA : DNA Stability over Stereochemistry in Pyrrolidine-Based Cationic Dual-Backbone PNA Analogues
Sharma, Ashwani,More, Shahaji H.,Ganesh, Krishna N.
, p. 1146 - 1155 (2021/02/09)
Modifications to the peptide nucleic acid (PNA) backbone has been well known to alter the thermodynamical parameters of PNA : DNA complexes to broaden their utility for different applications. Electrostatic interactions between a modified PNA having a positively charged backbone and the negatively charged DNA has been shown to enhance thermal stabilities of PNA : DNA complexes at various instances. On the other hand, chiral introduction in PNA backbone leads to stereochemical preference that affects binding properties. However, the interplay between electrostatics and stereochemistry has not been systematically studied so far. Herein, we report the synthesis and biophysical characterization of cationic PNA named dapPNA, first of its kind, having a dual PNA backbone constituting of a pyrrolidine ring having a β-substitution. One of the aims of this study was to investigate the role of electrostatics over stereochemical preferences. The results show that electrostatic attraction between cationic dapPNA and negatively charged DNA overcomes the unfavorable stereochemical effects and enhances stability of PNA : DNA complexes. Moreover, two different PNA backbones derived from a single PNA monomer expands the repertoire of pyrrolidine based PNA analogues.
Preorganized helical chirality controlled homochiral self-assembly and circularly polarized luminescence of a quadruple-stranded Eu2 L 4 helicate
Cheng, Zhenyu,Gao, Ting,Han, Guoying,Li, Hongfeng,Yan, Pengfei,Yao, Yuan,Zhou, Yanyan
, p. 3312 - 3320 (2020/03/23)
β-Diketones are one of the most widely used ligands for sensitizing the luminescence of lanthanide complexes due to their excellent sensitization abilities. However, the difficulties in introducing chiral groups to take part in the electronic transitions of conjugated systems limit their application in lanthanide circularly polarized luminescence (CPL) materials. In view of the inherent chirality of the helical structure, herein, a pair of homochiral quadruple-stranded helicates, Eu2L4, is assembled based on chiral bis-β-diketonate ligands, wherein the two point chirality centers in the spacer preorganize the helical conformation of the ligand (3S,4S)/(3R,4R)-3,4-bis(4,4′-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenoxyl)-1-benzylpyrrolidine, LSS/LRR. X-ray crystallographic analyses reveal that the R,R configurations of the chiral carbons in the spacer induce the M helical sense of the ligand, while the S,S configurations induce the P helical sense. Through the comprehensive spectral characterization in combination with semiempirical geometry optimization using the Sparkle/RM1 model, it is confirmed that the preorganized ligands successfully control the homochirality of the helicates. Moreover, the mirror-image CD and CPL spectra and NMR measurements confirm the formation of enantiomeric pairs and their diastereopurities in solution. Detailed photophysical and chiroptical characterization studies reveal that the helicates not only exhibit intense circularly polarized luminescence (CPL) with |glum| values reaching 0.10, but also show a high luminescence quantum yield of 34%. This study effectively combines the helical chirality of the helicates with the excellent sensitization ability of the β-diketones, providing an effective strategy for the syntheses of chiral lanthanide CPL materials.
Enantiospecific Synthesis of (3 R,4 R)-1-Benzyl-4-fluoropyrrolidin-3-amine Utilizing a Burgess-Type Transformation
Widlicka, Daniel W.,Gontcharov, Alexander,Mehta, Ruchi,Pedro, Dylan J.,North, Robert
, p. 1970 - 1978 (2019/08/22)
Manufacture of an EGFR inhibitor required the asymmetric synthesis of a key 3,4-trans-substituted pyrrolidine suitable for pilot-plant scale. The initial synthetic route utilized reagents and intermediates that posed safety concerns due to their energetic potential and then required supercritical fluid chromatography to access the desired single enantiomer. Burgess-type reagents provide tremendous utility in organic synthesis but see limited use on large scales because of their high cost and instability. Nevertheless, extensive process development led to a scale-friendly process where in situ formation of a Boc-Burgess reagent enabled access to a chiral cyclic sulfamate from inexpensive materials. ReactIR monitoring was used to study intermediate stability and enabled processing on a multikilogram scale. The sulfamate was converted to trans-3-fluoro-4-aminopyrrolidine 1 with complete stereospecificity. Intermediate crystallinity offered purity control points where byproducts and impurities were rejected, avoiding the need for chromatography.