Syntheses and NMR behavior of calix[4]quinone and calix[4]hydroquinone
摘要:
Calix[4]quinone (7) and calix[4]hydroquinone (6) have been synthesis using three different synthetic pathways. The first pathway to 7 from calix[4]arene (1) consists of six steps: acetylation, Fries rearrangement, Baeyer-Villiger oxidation after acetylation, hydrolysis, and oxidation. The second pathway to 7 from 1 consists of four steps: acetylation, Fries rearrangement, reaction of the product obtained by Fries rearrangement with sodium azide, and oxidation. The third pathway to 7 from 1 is most convenient and consists of three steps: diazo coupling reaction, reduction, and oxidation. The NMR behavior of 6 and 7 is described.
Friedel–Crafts acylation of 25,27-dialkoxycalix[4]arenes has been studied. Direct acylation of de-tert-butylated calixarene using acyl chlorides and AlCl3 in 1,2-dichloroethane provided the corresponding diacyl derivatives regioselectively in high yields. Furthermore, ipso-substitution in the tert-butylated series under the same reaction conditions is possible, albeit in lower yields. As indicated
Energy-Transfer Luminescence of Lanthanide Ions Encapsulated in Calix[4]arenes. Correlation between the Energy Level of Sensitizers and the Quantum Yield
作者:Hitoshi Matsumoto、Seiji Shinkai
DOI:10.1246/cl.1994.901
日期:1994.5
It was shown that the Tb3+ and Eu3+ complexes of 5,11,17,23-tetraacetyl-25,26,27,28-tetrakis(N,N-diethylaminocarbonylmethoxy)calix[4]arene give the high luminescence quantum yields (Φ = 0.164 for Tb3+ and 0.017 for Eu3+). The mechanistic investigations established that the high quantum yields are due to the energy level suitable to the energy-transfer and the presence of the carbonyl groups which mediate the intersystem crossing.
Calixbenoquin: Calixarene-Based Cluster of Monobenzone as a New Anti-Tyrosinase Agent
作者:Fazel Nasuhi Pur
DOI:10.1007/s11094-022-02777-x
日期:2022.12
Tyrosinase, copper-containing glycoprotein, is a key enzyme in the biosynthesis of melanin pigment from L-tyrosine. The excessive production of melanin in the skin due to skin disorders, such as melasma, is of great importance. Therefore, tyrosinase inhibitors are used for treatments of them. One of these inhibitors is monobenzone (benoquin) as a skin whitening agent, which has a phenolic structure. The phenolic structure of this drug, prompted the author to design its novel calix[4]arene-based cluster in a chalice-shaped structure. Therefore, the present study reports the synthesis and in vitro anti-tyrosinase of the chalice-shaped cluster of benoquin (namely calixbenoquin) in comparison to its simple drug unit (benoquin) as the reference medication. The synthetic route included chemical modification of the calix[4]arene structure by grafting four hydroxyl and benzyloxy groups on the upper and the lower rim of the calix[4]arene scaffold, respectively. The in vitro biological results showed an enhanced (about 4.5-fold) anti-tyrosinase activity for the calixarene-based cluster (calixbenoquin) in relation to its phenolic monomer (benoquin). Therefore, compared to benoquin, calixbenoquin with improved bioactivity can be considered as a new melanogenesis inhibitor with low dose range. These improved pharmaceutical effects are probably attributed to the clustering effect and improved interaction of four impacted benoquin units of the cluster with the active site of tyrosinase.