1114-34-7Relevant articles and documents
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Glatthaar,Reichstein
, p. 80 (1935)
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Two new dammarane monodesmosides from Centella asiatica
Weng, Xiao-Xiang,Shao, Yan,Chen, Yun-Yan,Gao, Wen,Cheng, Liang,Kong, De-Yun
, p. 749 - 755 (2011)
Two new dammarane monodesmosides centellosides A (1) and B (2), and two new natural products ginsenosides Mc (10) and Y (11), together with 11 known compounds (3-9 and 12-15) reported for the first time from this genus, were isolated from the whole plants of Centella asiatica. All structures were elucidated by spectroscopic techniques and chemical methods, and compared with literature values. All the isolated compounds were evaluated in vitro for cytotoxicity.
An Effective Heterogeneous Catalyst of [BMIM]3PMo12O40 for Selective Sugar Epimerization
Bayu, Asep,Yoshida, Akihiro,Karnjanakom, Surachai,Zuo, Zhijun,Hao, Xiaogang,Abudula, Abuliti,Guan, Guoqing
, p. 383 - 389 (2018)
The development of heterogeneous catalysts for the epimerization of sugars has received much less attention than that for the isomerization of sugars. To date, molybdates are the most effective catalysts for the epimerization of sugars, although they lack stability toward hydrolysis of their active sites in water. To solve the issue of the formation of a highly water-soluble heteropolyblue (PMored) for phosphomolybdates (PMos) in aqueous reaction systems, herein, a 1-butyl-3-methylimidazolium phosphomolybdate ([BMIM]3PMo12O40) was synthesized through an ion-exchange method. This catalyst was effective and selective for the C2-epimerization of sugars under mild reaction conditions (red was detected by means of UV/Vis spectroscopy. Moreover, the catalyst can be simply separated by filtration and reused for at least eight cycles without a drop in catalytic activity. XRD, FTIR, and X-ray photoelectron spectroscopy measurements indicate that the catalyst is stable under the reaction conditions. In a comparison of the catalytic activity and surface wettability with those of other PMo salts, that is, 1-ethyl-3-methylimidazolium phosphomolybdate ([EMIM]3PMo12O40), 1-hexyl-3-methylimidazolium ([HexMIM]3PMo12O40), [choline]3PMo12O40, and cetyltrimethylammonium phosphomolybdate ([CTA]3PMo12O40), it is found that [BMIM]3PMo12O40 has more appropriate hydrophobic–hydrophilic balance, which should be responsible for better catalytic activity and stability.
Xylans are a valuable alternative resource: Production of d-xylose, d-lyxose and furfural under microwave irradiation
Hricovíniová, Zuzana
, p. 1416 - 1421 (2013)
The influence of microwave irradiation on hydrolysis of xylan and simultaneous epimerization of the d-xylose to d-lyxose has been studied. An acidic solution of xylan was treated with catalytic amount of sodium molybdate and the composition of the reaction mixture was analyzed. Short reaction times of hydrolysis and subsequent epimerization reaction provided an equilibrium reaction mixture of d-xylose and d-lyxose (1.6:1) without significant formation of undesirable side products. Obtained pentoses can be reduced to the corresponding alditols (d-xylitol and d-lyxitol) in very good yields (88% and 85%) or can be further dehydrated to furfural (53%). Combined use of Mo(VI) catalyst and microwave irradiation allows better conversions and substantial reduction of reaction times (400-fold) compared to that obtained by conventional heating. Studied stereospecific transformation of xylan proceeds with high selectivity, short reaction times and very good yields that makes this approach attractive also for preparative purposes.
Three new cycloartane triterpenoids from Astragalus bicuspis
Jan, Saleem,Abbaskhan, Ahmed,Musharraf, Syed Ghulam,Sattar, Samina A.,Samreen,Resayes, Saud I.,Al-Othman, Zeid A.,Al-Majid, Abdullah M.,Atta-Ur-Rahman,Choudhary, M. Iqbal
, p. 1829 - 1834 (2011)
Three new cycloartane triterpenoids have been isolated from Astragalus bicuspis Fisch. Their structures were elucidated as 23(R),24(S),25(R),26(S)-16/ 23,23/26,24/25-triepoxy-26-hydroxy-9,19-cyclolanosta-3,6-dione (1), 6,23,24,25-tetraol-16-acetoxy-23(R),24(R)-9,19-cyclanosta-3-one (2), and 6,23,24,25-tetraol-16-acetoxy-23(R),24(R)-9,19-cyclolanosta-3-O-xyloside (3), based on their spectroscopic analysis. All cycloartane tritepenoids exhibited weak cytotoxicities against 3T3 fibroblast cells as compared to the standard drug cycloheximide. Compounds 3 and 4 were also tested for their antileishmanial potential, and a weak activity was observed against promastigotes of Leishmania major. Georg Thieme Verlag KG Stuttgart · New York.
Efficient Epimerization of Aldoses Using Layered Niobium Molybdates
Takagaki, Atsushi,Furusato, Shogo,Kikuchi, Ryuji,Oyama, S. Ted
, p. 3769 - 3772 (2015)
Both non-acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24-29 %. The layered mixed oxides functioned as heterogeneous catalysts and could be reused without loss of activity, whereas bulk molybdenum oxide MoO3 was completely dissolved during the reaction. A 13C substitution experiment showed that the reaction proceeds through a 1,2-rearrangement mechanism. The surface Mo octahedra were responsible for the activity. The layered HNbMoO6 could also afford mannose from cellobiose through hydrolysis and successive epimerization.
Tin, molybdenum and tin-molybdenum oxides: Influence of Lewis and Bronsted acid sites on xylose conversion
Meneghetti, Mario R.,Meneghetti, Simoni M. P.,Pryston, Dhara B. A.,da Silva Avelino, Débora Olimpio,dos Santos, Thatiane V.
, (2021/11/16)
In this study, tin oxide (SnO2), molybdenum oxide (MoO3) and a mixed oxide based on tin and molybdenum (respectively, Sn100, Mo100 and SnMo25, synthesized by the impregnation method) were applied in xylose conversion. The best results were obtained employing Mo100 and SnMo25. In the presence of SnMo25, after 0.5 h, xylose conversions of 39.5%, 34.1% and 63.4% were obtained, respectively, at 110, 130 and 150 °C. For Mo100, conversions of 49.6%, 71.8% and 85.3% were attained under the same reaction conditions, showing that Mo100 provided the best conversion results. However, with the use of this catalyst there was an increase in the amount of soluble and insoluble polymeric material. In terms of the soluble products formed from xylose, depending on the reaction condition were detected xylulose (X), lyxose (L) and furfural (FUR), glyceraldehyde (GL), pyruvaldehyde (PYR), glycoaldehyde (GLYC), dihydroxyacetone (DHA), lactic acid (AL), levulinic acid (LA) and acetic acid (AA). However, with the use of Sn100 or without a catalyst (systems with low conversions) there was mainly the formation of lyxose. The use of Mo100 and SnMo25 (systems which exhibit high acidity) leads mainly to isomerization, epimerization and dehydration reactions, as in the case of the retro-aldol pathway and furfural conversion, highlighting the importance of Lewis and Bronsted acid sites in relation to modulating the selectivity of the systems.
