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Komissarova, N. G.; Belenkova, N. G.; Спирихин, Л. В.; Shitikova, O. V.; Yunusov, M. S.

doi:10.1023/a:1015733832373

Cited by 19 publications

(10 citation statements)

References 6 publications

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“…Protocols for betulin oxidation into its corresponding C(28)‐aldehyde 2 are readily available in literature [31–44] . Among these there are mostly Anelli [31–36] and Jones [31,34,37–43] type oxidations employed, both coming along with several drawbacks.…”

Section: Resultsmentioning

confidence: 99%

“…Protocols for betulin oxidation into its corresponding C( 28)aldehyde 2 are readily available in literature. [31][32][33][34][35][36][37][38][39][40][41][42][43][44] Among these there are mostly Anelli [31][32][33][34][35][36] and Jones [31,34,[37][38][39][40][41][42][43] type oxidations employed, both coming along with several drawbacks. In particular, the Jones oxidation and related transformations suffer from the use of highly toxic/mutagenic chemicals and a poor discrimination between the primary and the secondary alcohol moieties, [31,34,[37][38][39][40][41][42][43] whereas N-oxyl radical-mediated oxidation frequently employs expensive terminal oxidizers [36] and co-catalysts [32] or reagents incompatible with the betulin 20(29)double bond (namely bleach).…”

Section: Resultsmentioning

confidence: 99%

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Electrosynthesis of Stable Betulin‐Derived Nitrile Oxides and their Application in Synthesis of Cytostatic Lupane‐Type Triterpenoid‐Isoxazole Conjugates

et al. 2021

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Novel lupane‐type triterpenoid‐isoxazole conjugates were designed by direct placing of isoxazole linker at C(17) of triterpenoid. The suggested synthetic sequence demonstrates successful combination of electro‐organic synthesis and conventional approaches. TEMPO‐mediated electrooxidation of betulin to betulinal was developed and optimized at boron‐doped diamond anodes with potassium acetate as inexpensive supporting electrolyte. Betulinal‐derived oxime was further selectively electro‐oxidized at a graphite anode to nitrile oxide, which proved to be stable and isolable species. The same reaction sequence was performed with 3β‐lupane‐3,28‐diol. Nitrile oxides were characterized by 15N NMR and X‐ray crystallography. The isolable nitrile oxides allowed creation of isoxazole library by 1,3‐dipolar cycloaddition reactions with various alkynes. Some of the title conjugates exhibit cytostatic properties against breast cancer cell line MCF7, glioblastoma multiform cell line U‐87 MG and lung carcinoma cell line A549 with growth inhibition (GI50) concentrations up to 11 μm, while being harmless to immortalized human fibroblasts hTERT (GI50 >100 μm).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Electrosynthesis of Stable Betulin‐Derived Nitrile Oxides and their Application in Synthesis of Cytostatic Lupane‐Type Triterpenoid‐Isoxazole Conjugates

et al. 2021

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“…The main method for the preparation of oxo-derivatives of betulin is its oxidation with toxic compounds: chromium (the Jones reagent [31], complexes with pyridinium chromates [32], etc. ), manganese (two-stage Swern-type oxidation of betulin and then with a solution of KMnO4 in a mixture 1,4-dioxane in water [33]), as well as mixtures of 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) with NaClO2-NaOCl [34].…”

Section: Introductionmentioning

confidence: 99%

Supported Silver Nanoparticles as Catalysts for Liquid-Phase Betulin Oxidation

et al. 2021

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Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver catalysts in betulin oxidation, silver was deposited on various alumina supports (γ-alumina and boehmite) using deposition–precipitation with NaOH and incipient wetness impregnation methods, followed by treatment in H2 or O2. Silver catalysts and the corresponding supports were characterized by X-ray diffraction, nitrogen physisorption, inductively coupled plasma optical emission spectroscopy, photoelectron spectroscopy and transmission electron microscopy. It was found that the support nature, preparation and treatment methods predetermine not only the average Ag nanoparticles size and their distribution, but also the selectivity of betulin oxidation, and thereby, the catalytic behavior of Ag catalysts. In fact, the support nature had the most considerable effect. Betulin conversion, depending on the support, increased in the following order: Ag/boehmite < Ag/boehmite (calcined) < Ag/γ-alumina. However, in the same order, the share of side reactions catalyzed by strong Lewis acid centers of the support also increased. Poisoning of the latter by NaOH during catalysts preparation can reduce side reactions. Additionally, it was revealed that the betulin oxidation catalyzed by nanosilver catalysts is a structure-sensitive reaction.

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“…Betulinic acid was synthesized by the oxidation of betulinic aldehyde with potassium permanganate. 24 A method for selective oxidation of betulin with pyridinium dichromate (PDC), pyridinium chlorochromate (PCC) or K 2 Cr 2 O 7 -9 M H 2 SO 4 in the presence of tetrabutylammonium bromide (TBAB) to betulinic aldehyde, or its mixture with betulonic aldehyde and ketol was developed by Komissarov et al 25 The yield of oxidation products did not exceed 75%. The method of obtaining betulonic acid by oxidation of betulin, in the first step with the Jones reagent in acetone, should also be mentioned.…”

Section: Introductionmentioning

confidence: 99%