769-85-7Relevant articles and documents
Red-Emissive Cell-Penetrating Polymer Dots Exhibiting Thermally Activated Delayed Fluorescence for Cellular Imaging
Algar, W. Russ,Christopherson, Cheyenne J.,Hudson, Zachary M.,Paisley, Nathan R.,Xiao, Zhujun
, p. 13342 - 13349 (2021)
Fluorescence imaging in living cells is key to understanding many biological processes, yet autofluorescence from the sample can lower sensitivity and hinder high-resolution imaging. Time-gated measurements using phosphorescent metal complexes can improve imaging, at the cost of potential toxicity from the use of heavy metals. Here, we describe orange/red-emitting polymer dots (Pdots) exhibiting thermally activated delayed fluorescence (TADF) for time-gated imaging. Inspired by the cell invasion mechanism of the HIV TAT protein, the Pdots were formed from block copolymers composed of a hydrophilic guanidine-rich block as a cell-penetrating peptide mimic, and a rigid organic semiconductor block to provide efficient delayed fluorescence. These all-organic polymer nanoparticles were shown to efficiently enter HeLa, CHO, and HepG2 cells within 30 min, with cell viabilities remaining high for Pdot concentrations up to 25 mg mL-1. Pdot quantum yields were as high as 0.17 in aerated water, with the Pdot structure effectively shielding the TADF emitters from quenching by oxygen. Colocalization experiments revealed that the Pdots primarily accumulate outside of lysosomes, minimizing lysosomal degradation. When used for fixed cellular imaging, Pdot-incubated cells showed high signal-to-background ratios compared to control samples with no Pdot exposure. Using time-resolved spectroscopy, the delayed emission of the TADF materials was effectively separated from that of both a biological serum and a secondary fluorescent dye.
Method for preparing single-configuration C-2-position-monosubstituted norbornene derivative
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, (2021/07/01)
The invention discloses a method for preparing a single-configuration C-2-position-monosubstituted norbornene derivative. The method comprises the following steps of: firstly, preparing exo-isomer enriched exo-isomer mixed 5-norbornene-2-carboxylic ester by taking commercial exo-isomer/endoisomer mixed 5-norbornene-2-carboxylic acid and large-steric-hindrance monohydric alcohol as raw materials; separating 5-norbornene-2-carboxylate with a single configuration through common column chromatography separation or fractionation; and finally, preparing the C-2-position-monosubstituted norbornene derivative with the single configuration from the separated 5-norbornene-2-carboxylate with the single configuration. The raw materials used in the invention are easy to obtain, the preparation process is simple, and the C-2-position-monosubstituted norbornene derivative with high purity (greater than 98%) and single configuration can be obtained.
New and facile synthesis of aminobicyclo[22.1]heptane-2-carboxylic acids
Kim, Taek-Soo,Seo, Seung-Yong,Shin, Dongyun
supporting information, p. 1243 - 1247 (2015/03/31)
Abstract A facile approach for the stereoselective synthesis of a- and b-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid is described. Substrate-controlled α-carboxylation of norbonene monoester delivered the asymmetric diester intermediate with high diastereoselectivity (up to 35:1). Sequential chemoselective ester cleavage, Curtius rearrangement, and hydrolysis gave the a- and b-isomers of 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid, respectively.
Diels-Alder reactions in room-temperature ionic liquids
Fischer,Sethi,Welton,Woolf
, p. 793 - 796 (2007/10/03)
The Diels-Alder cycloaddition reaction between methyl acrylate and cyclopentadiene has been investigated in a number of air and moisture stable ionic liquids. The endo/exo ratio of the reaction has been used as an initial probe of the nature of the solvents.
Novel Potassium-Channel Openers: Preparation and Pharmacological Evaluation of Racemic and Optically Active N-(6-Amino-3-pyridyl)-N'-bicycloalkyl-N"-cyanoguanidine Derivatives
Eda, Masahiro,Takemoto, Tadahiro,Ono, Shin-ichiro,Okada, Takehiro,Kosaka, Keigo,et al.
, p. 1983 - 1990 (2007/10/02)
The previous paper reported on the synthesis and pharmacological evaluation of N-(6-amino-3-pyridyl)-N'-bicycloalkyl-N"-cyanoguanidine derivatives, from among which three compounds were selected as potent potassium-channel openers. In the present study, selected compounds were tested for antagonism of potassium-induced contraction of rat aorta, hypotensive activity in normotensive rats, and diuretic activity in spontaneously hypertensive rats. This led to further evaluation of compound (+/-)-10 and selection of (+)-N-(6-amino-3-pyridyl)-N'-hept-2-yl>-N"-cyanoguanidine ((+)-10) (AL0670) for development as an antihypertensive agent. Although AL0670 is regarded as a pinacidil-type K+-channel opener, it showed different pharmacological and conformational profiles from pinacidil.
Stereoselection in Thermal Asymmetric Diels-Alder Reactions. Electronic vs Steric Effects
Stammen, Blanda,Berlage, Ulrich,Kindermann, Richard,Kaiser, Manfred,Guenther, Barbara,et al.
, p. 6566 - 6575 (2007/10/02)
Experimental evidence was found for an electronic contribution favoring the cisoid conformation of α,β-unsaturated carbonyl compounds in thermal Diels-Alder transition states.
Enzymatic optical resolution of norbornanecarboxylic esters using Pig Liver Esterase
Gastel, F. J. C. van,Klunder, A. J. H.,Zwanenburg, B.
, p. 175 - 184 (2007/10/02)
The hydrolysis of a series of norbornane-type carboxylic esters catalyzed by pig liver esterase (PLE) has been investigated.It was found that an exo-ester function (syn to the C7 methylene group) is hydrolyzed with high preference.Enantioselective hydrolysis can be accomplished when a vicinal carbonyl-containing function (ester, formyl, acetyl) is present in a trans position with respect to the exo ester.The regiospecifity of the enzymatic hydrolysis has been used for the separation of exo/endo mixtures of the cycloadducts derived from cyclopentadiene and alkene esters.The regiospecifity and enantioselectivity of the enzymatic hydrolysis of norbornane-type esters were analyzed in terms of Tamm's substrate model and also by Griengl's method.
Transformations of unsaturated acyclic sugars into enantiomerically pure norbornene derivatives
Horton, Derek,Usui, Takayuki
, p. 33 - 49 (2007/10/02)
The C7 acyclic unsaturated-sugar ester 1, derived from L-arabinose, and its enantiomer serve as convenient dieneophiles for chirality transfer for synthesis of optically pure carbocyclic derivatives through cycloaddition reactions.Reaction of 1 with cyclopentadiene may be controlled to give preparative access to the 5,6-disubstituted norbornene adducts 4a, 5a and 7a, according to the conditions used.The distribution of the four possible isomeric products from this cycloaddition was quantitated, and the effect of substitutional variation on the precursor dienophile 1 was also examined.Adducts 4a and 5a were transformed into such substituted carbocycles of known absolute configuration as the methyl esters (11 and 12) of norbornene (bicyclohept-2-ene)-6-carboxylic acid and nortricyclane (tricyclo2,6>heptane)-3-carboxylic acid in optically pure form, specifically through decarbonylation reactions using RhCl(PPh3)3 (Wilkinson's complex) and Cl.The optical purity of 12 was established by the use of a chiral lanthanide shift-reagent.
INFLUENCE OF POLAR GROUPS IN THERMAL AND LEWIS ACID PROMOTED ASYMMETRIC DIELS-ALDER ADDITIONS: LACTIC ACID DERIVATIVES AS PRACTICAL HIGHLY SELECTIVE AND CONFIGURATIONALLY DICHOTOMIC REAGENTS
Poll, Thomas,Helmchen, Guenther,Bauer, Bernd
, p. 2191 - 2194 (2007/10/02)
Diels-Alder reactions of the acrylate of (S)-ethyl lactate with cyclopentadiene proceed with diastereoface-selectivity of up to 85:15 (non catalyzed) and 93:7 (TiCl4-promoted).Depending on the Lewis acid, products of inverse configuration are obtained.In conjunction with facile product analysis by LC, effective means for suppression of the polymerization of diene, and virtually epimerization-free ester hydrolysis these findings constitute a method for large scale practical applications of the asymmetric Diels-Alder reaction.
Stereochemistry of Alkylation of Carboxylic Acid Salt and Ester α Anions Derived from Cyclic Systems.
Krapcho, A.Paul,Dundulis, Edward A.
, p. 3236 - 3245 (2007/10/02)
A stereochemical study of the alkylation of α-lithiated carboxylate salts and esters has been performed.The α anions derived from the bicyclic acids exo-1, endo-1, and 7 (R=H) and the esters 4 and 7 (R=CH3) yield predominantly exo alkylation.As an example, the α anion derived from ester 7 (R=CH3) on treatment with CH3I yields exo-8 (R=R'=CH3) and endo-9 (R=R'=CH3) in a 97:3 ratio, a highly stereoselective reaction.Addition of TMEDA to the reactions involving the α anions derived from exo- or endo-1 did not change the stereochemical alkylation results.The α anions derived from the substituted cyclohexanecarboxylic acids 10, 13, 16, 19, or 22 (where R=H in each case) on methylation yield more axial methylation (axial/equatorial ratios of 0.4-2.7) than the α anions derived from the methyl esters corresponding to these acids.The α anions from the esters yield predominantly equatorial methylated products (e/a ratios varying from 4 to 9).The reasons for the different stereochemical results are discussed.
