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1.
Chemistry ; 30(40): e202401564, 2024 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-38797716

RESUMO

We report on the elastic and photodynamic properties of (E)-1,2-bis(pyridinium-4-yl)ethene dinitrate [H2Ebpe](NO3)2, whose needle-like crystals can be reversibly deformed by applying external mechanical stress. The macro-scale mechanical properties of [H2Ebpe](NO3)2 crystals were quantified by a three-point bending test, which gave a stress-strain curve with an elastic modulus of 1.18 GPa, and its values are lower than those of other flexible elastic organic crystals. It can also be reversibly bent through the [2+2] cycloaddition reaction of the olefin moiety, depending on the direction of UV irradiation.

2.
Chem Pharm Bull (Tokyo) ; 72(3): 294-297, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38462461

RESUMO

Aiming to synthesize a cyclic hexaamide, 4-bromo-3-(isobutylamino)benzoic acid was subjected to self-condensation reactions in the presence of either dichlorotriphenylphosphorane in 1,1,2,2-tetrachloroethane or tetrachlorosilane in pyridine. However, instead of the targeted cyclic hexaamide, the cyclic triamide and the cyclic tetraamide were obtained. The cyclic hexaamide was successfully synthesized via the self-condensation of the dimer, which was synthesized in five steps from 4-bromo-3-(isobutylamino)benzoic acid. A thorough screening of the self-condensation conditions was performed to improve the yield of the target macrocycle. In addition, the linear hexamer was synthesized by stepwise deprotection and condensation, and its cyclization afforded the cyclic hexaamide in good yield.


Assuntos
Benzoatos , Ácido Benzoico , Ciclização , Amidas/química , Benzoatos/química
3.
RSC Adv ; 12(40): 26411-26417, 2022 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-36275098

RESUMO

A coronene amide analogue was synthesized in six steps using an improved method at the final biarylation step. The key to the progress of palladium-mediated biarylation involved the introduction of three methyl groups to suppress the undesired reaction and the use of tri-tert-butylphosphine as the ligand for palladium. Single-crystal X-ray analysis revealed that the core unit of the coronene analogue has a non-planar structure.

4.
Chem Pharm Bull (Tokyo) ; 70(2): 187-191, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35110441

RESUMO

A new pentacyclic monoterpenoid indole alkaloid glycoside named secorubenine (1) was isolated from the heartwood of Adina rubescens, collected in Indonesia. The structure was elucidated by spectroscopic analysis and chemical modification of isolated secorubenine (1). The bioinspired enantioselective total synthesis of 1 was accomplished in 12 steps, whereafter its structure was determined and the absolute stereochemistry was confirmed.


Assuntos
Apocynaceae/química , Indonésia , Estrutura Molecular , Estereoisomerismo
5.
Angew Chem Int Ed Engl ; 59(32): 13414-13422, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32364625

RESUMO

A collective synthesis of glycosylated monoterpenoid indole alkaloids is reported. A highly diastereoselective Pictet-Spengler reaction with α-cyanotryptamine and secologanin tetraacetate as substrates, followed by a reductive decyanation reaction, was developed for the synthesis of (-)-strictosidine, which is an important intermediate in biosynthesis. This two-step chemical method was established as an alternative to the biosynthetically employed strictosidine synthase. Furthermore, after carrying out chemical and computational studies, a transition state for induction of diastereoselectivity in our newly discovered Pictet-Spengler reaction is proposed. Having achieved the first enantioselective total synthesis of (-)-strictosidine in just 10 steps, subsequent bioinspired transformations resulted in the concise total syntheses of (-)-strictosamide, (-)-neonaucleoside A, (-)-cymoside, and (-)-3α-dihydrocadambine.


Assuntos
Alcaloides de Triptamina e Secologanina/síntese química , Ciclização , Oxirredução , Estereoisomerismo
6.
Chemistry ; 25(38): 8996-9000, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-31069870

RESUMO

The first enantioselective total syntheses of (-)-secologanin (1), (-)-5-carboxystrictosidine (2), and (-)-rubenine (3) were accomplished in 10, 9, and 14 steps, respectively. The key transformation in the synthesis of 1 was a sequential anti-selective organocatalytic Michael reaction/Fukuyama reduction/spontaneous cyclization to form an optically active dihydropyran ring. In addition, the secologanin tetraacetate (16), which is a potential key intermediate for the bioinspired divergent syntheses of monoterpenoid indole alkaloids, was prepared in gram-scale in seven steps. The total syntheses of 2 and 3, which are classified as glycosylated monoterpenoid indole alkaloids, were achieved through bioinspired transformations such as a diastereoselective Pictet-Spengler reaction, a site- and stereoselective epoxidation, and a site-selective epoxide ring-opening followed by a lactonization reaction.

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