scholarly journals A Simple and Efficient Method for the Partial Synthesis of Pure (3R,3’S)-Astaxanthin from (3R,3’R,6’R)-Lutein and Lutein Esters via (3R,3’S)-Zeaxanthin and Theoretical Study of Their Formation Mechanisms

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1386 ◽  
Author(s):  
Eloy Rodríguez-deLeón ◽  
J. Jiménez-Halla ◽  
José Báez ◽  
M. Bah

Carotenoids are natural compounds that have important roles in promoting and maintaining human health. Synthetic astaxanthin is a highly requested product by the aquaculture industry, but natural astaxanthin is not. Various strategies have been developed to synthesize this carotenoid. Nonetheless, these approaches have not only provided limited global yields, but its main commercial source also carries several health risks for humans. In this contribution, the one-pot base-catalyzed reaction of (3R,3’R,6’R)-lutein (1) esters has resulted in a successful isomerization process to easily obtain up to 95% meso-zeaxanthin (2), which in turn is oxidized to (3R,3’S)-astaxanthin (3) with a global yield of 68%. The same oxidation performed with UV irradiation (365 nm) for 5 min provided the highest global yield (76%). These chemical transformations have also been achieved with a significant reduction of the health risks associated with its potential human consumption. Furthermore, this is the first time only one of the configurational isomers has been obtained semisynthetically. The poorly understood formation mechanisms of these two compounds were also investigated using Density-Functional Theory (DFT) calculations. These theoretical studies revealed that the isomerization involves a base-catalyzed deprotonation at C-6’, followed by C-4’ protonation, while the oxidation occurs via free radical mechanisms.

2016 ◽  
Vol 6 (12) ◽  
pp. 4283-4293 ◽  
Author(s):  
Yufeng Ren ◽  
Bo Yang ◽  
Xiali Liao

The one-pot three-component synthesis of 2-amino-4H-chromenes was accomplished by supramolecular catalysis with well-designed amino-appended β-cyclodextrins (ACDs) in water, while the key role of amino side chains in chemoselectivity was determined for the first time.


2021 ◽  
Author(s):  
Majji Shankar ◽  
Arijit Saha ◽  
Somratan Sau ◽  
Arghadip Ghosh ◽  
Vincent Gandon ◽  
...  

An unconventional cobalt(III)-catalyzed one-pot domino double annulation of aryl thioamides with unactivated alkynes is presented. Sulfur (S), nitrogen (N), and o,o'-C-H bonds of aryl thioamides are involved in this reaction, enabling access to rare 6,6-fused thiopyrano-isoquinoline derivatives. A reverse ‘S’ coordination over more conventional ‘N’ coordination of thioamides to Co-catalyst specifically regulates the formation of four [C-C and C-S at first and then C-N and C-C] bonds in a single operation, a concept which is uncovered for the first time. The power of the N-masked methyl phenyl sulfoximine (MPS) directing group in this annulation sequence is established. The transformation is successfully developed, building a novel chemical space of structural diversity (56 examples). In addition, late-stage annulation of biologically relevant motifs and drug candidates are disclosed (17 examples). Preliminary photophysical properties of thiopyrano-isoquinoline derivatives are discussed. Density functional theory (DFT) studies authenticate the participation of a unique 6p-electrocyclization of a 7-membered S-chelated cobaltacycle in the annulation process.<br>


2020 ◽  
Author(s):  
Esra Demir ◽  
Özlem Sarı ◽  
Yasin Çetinkaya ◽  
Ufuk Atmaca ◽  
Safiye Sağ Erdem ◽  
...  

The one-pot reaction of chlorosulfonyl isocyanate (CSI) with epoxides having substituted phenyl, benzyl and fused cyclic alkyl groups in different solvents under mild reaction conditions without additives and catalysts was studied. Oxazolidinones and five-membered cyclic carbonates were obtained with a ratio close to (1:1) in the cyclization reactions. The best reaction conversion for the synthesis of these compounds was carried out in dichloromethane (DCM). The method presented here has distinct advantageous over the existing methods such as one-pot reaction, shorter reaction times, metal-free reagent, good yields and very simple purification method. The mechanism for the cycloaddition reactions has been elucidated using density functional theory (DFT) method at the M06-2X/6-31+G(d,p) level. The investigation of the potential energy surfaces associated with two possible channels leading to oxazolidinones and five-membered cyclic carbonates revealed that the cycloaddition reaction takes place through an asynchronous concerted mechanism in gas phase and in DCM.


2021 ◽  
Author(s):  
Rentian Guan ◽  
Shuai Zhang ◽  
Xiaoyu Fan ◽  
Xiaodong Shao ◽  
Yingying Hu ◽  
...  

Abstract It was the first time to report the aggregation induced emission (AIE) of acetaldehyde (AA) on the surface of carbonized polymer dots (CPDs) with the auxiliary of Tb3+. Based on the AIE of AA, a turn-off-on fluorescence method was established for AA detection using the porous CPDs-Tb3+ system. The one-pot hydrothermal method was used to obtain CPDs, using milk and polyethyleneimine (PEI) as precursors. In the presence of Tb3+, CPDs aggregated immediately, and the fluorescence intensity decreased obviously for the precipitate. AA can effectively embed on the surface of CPDs-Tb3+ due to the porous structure. AA displayed obviously blue fluorescence with excitation wavelength at 370 nm (emission peak at 460 nm), while there was no fluorescence peak when excited at 460 nm. In the CPDs-Tb3+ solution, AA exhibits obvious fluorescence enhancement effect (lex 460 nm, lem 545 nm). And then, AA can be determined by the turn-off-on system based on the linear relationship between fluorescence enhancement and the concentration of AA ranging from 0.04 mM to 42.48 mM. The limit of detection (LOD) was 0.02 mM. The turn-off-on system was successfully applied to determine AA in wine samples. The strategy may be exploited to monitor AA in more drinking or foodstuff samples.


2021 ◽  
Author(s):  
Joaquín García-Álvarez ◽  
Vito Capriati ◽  
Luciana Cicco ◽  
Javier González-Sabín ◽  
Alejandro Presa Soto ◽  
...  

The one-pot/two-step combination of enzymes and polar organometallic chemistry in aqueous media is for the first time presented as a proof-of-concept study. The unprecedented combination of the catalytic oxidation of...


2020 ◽  
Vol 18 (30) ◽  
pp. 5891-5896 ◽  
Author(s):  
Kaushik Chakrabarti ◽  
Kuheli Dutta ◽  
Sabuj Kundu

The Ru(ii) complex catalysed direct transformation of acyl azides into N-methylamines was developed for the first time using methanol via the one-pot Curtius rearrangement and borrowing hydrogen methodology.


Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4252 ◽  
Author(s):  
Rungthip Kunthom ◽  
Nobuhiro Takeda ◽  
Masafumi Unno

The one-pot synthesis of an unsymmetrical double-decker siloxane with a novel structure via the reaction of double-decker tetrasodiumsilanolate with 1 equiv. of dichlorotetraphenyldisiloxane in the presence of an acid is reported herein for the first time. The target compound bearing all phenyl substituents on the unsymmetrical siloxane structure was successfully obtained, as confirmed by 1H-NMR, 13C-NMR, 29Si-NMR, IR, MALDI-TOF, and X-ray crystallography analyses. Additionally, the thermal properties of the product were evaluated by TG/DTA and compared with those of other siloxane cage compounds.


RSC Advances ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 4671-4681 ◽  
Author(s):  
Ewa Janiszewska ◽  
Agnieszka Held ◽  
Krystyna Nowińska ◽  
Stanisław Kowalak

Efficient SBA-3 vanadosilicate catalysts for propene oxidation obtained for the first time by the one-pot synthesis.


2021 ◽  
Author(s):  
Baogang Wang ◽  
Lilong Zhang ◽  
Na Wang ◽  
Wenmeng Duan ◽  
Weiwei Tang

A series of carbon dots modified by ionic liquids with various anion species (CDs-ILs-X) were facile synthesized by the one-pot pyrolysis method and subsequent anion exchange processes, where the X-...


RSC Advances ◽  
2021 ◽  
Vol 11 (37) ◽  
pp. 22751-22755
Author(s):  
Vahid Khakyzadeh ◽  
Ahmad Reza Moosavi-Zare ◽  
Sahra Sheikhaleslami ◽  
Amir Ehsani ◽  
Salbin Sediqi ◽  
...  

Water was magnetized via an external magnetic field and employed, for the first time, as a solvent in green preparation of 3,4-dihydropyrimidin-2(1H)-ones by the one-pot three-component condensation reaction using boric acid as a catalyst.


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