- Selective cleavage of methoxy protecting groups in carbohydrates
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The selective cleavage of methoxy protecting groups next to hydroxy groups is achieved using a radical hydrogen abstraction reaction as the key step. Under the reaction conditions, the hydroxy group generates an alkoxyl radical that reacts with the sterically accessible adjacent methoxy group, which is transformed into an acetal. In the second step, the acetals are hydrolyzed to give alcohols or diols. A one-pot hydrogen abstraction-hydrolysis procedure was also developed. Good yields were usually achieved, and the mild conditions of this methodology were compatible with different functional groups and sensitive substrates such as carbohydrates.
- Boto, Alicia,Hernandez, Dacil,Hernandez, Rosendo,Suarez, Ernesto
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p. 1938 - 1948
(2007/10/03)
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- THE STEROIDAL GLYCOSIDES OF THE FLOWERS OF YUCCA GLORIOSA
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Four steroidal compounds were isolated from the fresh flowers of Yucca gloriosa and their structures were elucidated as tigogenin 3-O-β-D-xylopyranosyl-β-lycotetraoside, gitogenin 3-O-β-D-xylopyranosyl-β-lycotetraoside, gitogenin 3-O-α-rhamnopyranosyl-β-lycotetroside and proto-type of gitogenin 3-O-β-D-xylopyranosyl-β-lycotetraoside, on the basis of physical and chemical investigation.Key Word Index - Yucca gloriosa; Liliaceae; tigogenin glycoside; gitogenin glycosides; furostanol glycoside.
- Nakano, Kimiko,Matsuda, Emi,Tsurumi, Kaori,Yamasaki, Tokushi,Murakami, Kotaro,et al.
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p. 3235 - 3240
(2007/10/02)
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- Five Steroidal Components from the Rhizomes of Polygonatum odoratum var. pluriflorum
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Five steroidal components (PO-a(1)-PO-e(5)) were obtained from the methanolic extract or its partial hydrolysate of the fresh rhizomes of Polygonatum odoratum var.Pluriflorum, and their chemical structures were characterized as (25 R and S)-spirost-5-en-3β,14α-diol, 3-O-β-D-glucopyranosyl-(1->2)-3)>-β-D-glucopyranosyl-(1->4)-β-D-galactopyranosyl(=β-lycotetraosyl)-(25 R and S)-spirost-5-en-3β,14α-diol, 3-O-β-lycotetraosyl-22-methoxy-(25 R and S)-furost-5-en-3β,14α,26-triol 26-O-β-D-glucopyranoside, 3-O-β-D-glucopyranosyl-(1->2)-3)>-β-D-glucopyranosyl(1->4)-β-D-galactopyranosyl-22-methoxy-(25 R and S)-furost-5-en-3β,14α,26-triol 26-O-β-D-glucopyranoside and 3-O-β-lycotetraosyl yamogenin, respectively.Moreover, (25 S)-spirost-5-en-3β,14α-diol (7) was isolated from a mixture of the (25 R) and (S) derivatives of PO-a (1) and it was designated as neoprazerigenin A.Keywords - Polygonatum odoratum var. pluriflorum; Liliaceae; neoprazerigenin A; spirostanol glycoside; furostanol glycoside.
- Sugiyama, Mari,Nakano, Kimiko,Tomimatsu, Toshiaki,Nohara, Toshihiro
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p. 1365 - 1372
(2007/10/02)
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- Steroidal glycosides of Tribulus terrestris Linn.
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Besides β-sitosterol-β-D-glucoside and dioscin, two new steroidal glycosides, neohecogenin glucoside and tribulosin, isolated from the aerial part of Tribulus terrestris Linn. were respectively shown to be neohecogenin-3-O-β-D-glucopyranoside (2) and neotigogenin-3-O-β-D-xylopyranosyl(1->2)-3)>-β-D-glucopyranosyl(1->4)-2)>-β-D-galactopyranoside (7).
- Mahato, Shashi B.,Sahu, Niranjan P.,Ganguly, Amar N.,Miyahara, Kazumoto,Kawasaki, Toshio
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p. 2405 - 2410
(2007/10/02)
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