13479-66-8Relevant articles and documents
Triterpene and steroidal glycosides of the genus Melilotus and their genins. VI. Melilotoside A2 and adzukisaponin v from the roots of M. tauricus
Khodakov
, p. 1024 - 1026 (2013/05/09)
Two triterpene glycosides of the oleanane series, melilotoside A 2 and previously known adzukisaponin V, were isolated from the roots of Melilotus tauricus (L.) Pall. (Fabaceae). The structures of the glycosides were proved based on chemical transformations. Melilotoside A2 had the structure soyasapogenol B 3-O-β-D-glucouronopyranoside; adzukisaponin V, soyasapogenol B 3-O-[α-L-rhamnopyranosyl-(1-2)-β-Dglucopyranosyl- (1-2)-β-D-glucuronopyranoside].
Hydroxy group acidities of partially protected glycopyranosides
Matwiejuk, Martin,Thiem, Joachim
scheme or table, p. 2180 - 2187 (2012/06/30)
A comprehensive acidity study of carbohydrate hydroxy groups has been carried out. Relative acidities (Ke) were determined spectrophotometrically for partially methylated methyl α-D- glycopyranosides. Apparently, the acidity is strongly affected by intramolecular hydrogen bonding as well as stereochemistry and solvation. By comparison with pKe and pKa values of aliphatic alcohols and polyols the first estimation of the pKa values for partially protected glycopyranosides was obtained. These findings contribute to the understanding of the relative reactivities of carbohydrate hydroxy groups.
Tandem epoxidation-alcoholysis or epoxidation-hydrolysis of glycals catalyzed by titanium(IV) isopropoxide or Venturello's phosphotungstate complex
Levecque, Pieter,Gammon, David W.,Kinfe, Henok Hadgu,Jacobs, Pierre,De Vos, Dirk,Sels, Bert
body text, p. 1557 - 1568 (2009/07/10)
Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr)4] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H2O 2]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr)4 was only effective in methanol as solvent, but gave methyl glycosides in high yields and high selectivities. The Venturello complex proved to be a very versatile and efficient catalyst. Apart from epoxidation-alcoholysis in alcoholic solvents it also showed activity in biphasic conditions to allow for glycosylation of long-chain alcohols and was very effective in the stereoselective dihydroxylation of benzylated glucal.
Intramolecular vinylsilane-oxocarbenium condensations: Concise assembly of cis-bicyclic ether arrays
Fearnley, Stephen Philip,Lory, Pedro
, p. 3507 - 3510 (2008/02/12)
Lewis acid-mediated intramolecular attack of vinylsilanes at tethered oxonium precursors 1 results in a rapid assembly of the cis-fused bicyclic ether species 3, with complete regio- and stereospecific control, and in some cases near-quantitative yield. C
Naphthyl 3,4,6-tri-O-methyl-β-D-glucopyranoside as a chiral auxiliary in an asymmetric 1,4-addition reaction
Chiappe, Cinzia,Lo Moro, Giacomo,Munforte, Paola
, p. 2311 - 2317 (2007/10/03)
Naphthyl 3,4,6-tri-O-methyl-β-D-glucopyranoside, easily synthesized from tri-O-acetyl-D-glucal, has been applied as a chiral auxiliary in an asymmetric Michael addition to the 2-O-crotonate. A very high facial diastereoselection (>95%) was obtained. No diastereoselection was observed when 1,3,4,6-tetra-O-methyl-β-D-glucopyranoside was used as the chiral auxiliary. A stereochemical model, taking into account steric shielding and π-stacking effects, is proposed on the basis of the observed results.
Chemistry of glucal halohydrins(II): An unusual protecting group effect in the competitive formation of formyl furanosides and methyl glycosides
Kozlowski, John S.,Marzabadi, Cecilia H.,Rath, Nigam P.,Spilling, Christopher D.
, p. 301 - 313 (2007/10/03)
A remarkable protecting group influence was observed in the base-induced reaction of protected halohydrins derived from D-glycals. Tri-O-methyl and tri-O-benzyl halohydrins react with cesium carbonate in methanol at room temperature to give methyl glycosides as the major product and unsaturated formyl furanosides as the minor product. Whereas, the tri-O-tert-butyldimethylsilyl (t-BuMe2Si)-protected halohydrins reacted with cesium carbonate in methanol at room temperature to give a mixture of epimeric formyl furanosides, and at reflux to give an unsaturated formyl furanoside, as the only products. The tri-O-methyl and tri-O-benzyl halohydrins react slowly at elevated temperature to give predominantly furans. In comparison, the tri-O-t-BuMe2Si halohydrins reacted completely after five minutes to give a mixture of epimeric formyl furanosides. The tri-O-t-BuMe2Si iodohydrins were oxidized to the corresponding iodolactones, which also underwent a based-induced ring contraction in methanol to give the furanose 1-methylcarboxylate esters.
The Chemistry of Glucal Halohydrins: The Effect of the Halide on Epoxide Formation
Marzabadi, Cecilia H.,Spilling, Christopher D.,Tyler, Lisa M.
, p. 6783 - 6796 (2007/10/02)
Chlorohydrins, bromohydrins, and iodohydrins, formed by hydroxyhalogenation of tri-O-methyl glucal, undergo base induced cyclization to give glucal epoxides.The mechanism of the cyclization reaction was probed using 1H NMR and deuterium incorporation studies.Cyclization and in situ trapping with Cs2CO3 in MeOD gave deuterated methyl 3,4,6-tri-O-methyl-α-D-mannoside and methyl 3,4,6-tri-O-methyl-β-D-glucoside, and an unsaturated aldehyde.These studies led to optimised stereoselectivity for the epoxide formation.Reaction of gluco bromohydrins with NaH or LiHMDS in THF at 5 deg C gave β-epoxide, and reaction of manno iodohydrins with KH and 18-crown-6 in toluene at -70 deg C gave α-epoxide.The epoxides were opened by reaction with sodium phenylthiolate to give phenyl 3,4,6-tri-O-methyl-1-thio-α-D-mannopyranoside (single isomer), and phenyl 3,4,6-tri-O-methyl-1-thio-β-D-glucopyranoside (>18:1), respectively.
ASTRAILIENIN A FROM ASTRAGALUS ILIENSIS
Yu-Qun, Chen,Guli, Azi,Yong-Rong, Luo
, p. 1941 - 1943 (2007/10/02)
A new triterpenoid glycoside, astrailienin A, was isolated from the roots of Astragalus iliensis.By heterogenous acid hydrolysis an aglycone was obtained which was identified as cycloastragenol.On the basis of spectral analysis and chemical reactions, the structure of the new compound was assigned as the 3-O-2)>-β-D-glucopyranoside of cycloastragenol.
Study on the constituents of Desmodium styracifolium.
Kubo,Hamada,Nohara,Wang,Hirayama,Ikegami,Yasukawa,Takido
, p. 2229 - 2231 (2007/10/02)
Two triterpenoid saponins (1 and 2) were isolated from Desmodii Herba [the dried whole plants of Desmodium styracifolium (Osbeck) Merr. (Leguminosae)] and their chemical structures were characterized as soyasaponin I and a new saponin, 3-O-[alpha-L-rhamnopyranosyl-(1----2)-beta-D-galactopyranosyl- (1----2)-beta-D-glucuronopyranosyl]soyasapogenol E, respectively, by chemical and spectroscopic means.
