- Beckmann rearrangement within the ring C of oleanolic acid lactone: Synthesis, structural study and reaction mechanism analysis
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Synthesis, spectral and X-ray analysis of three compounds, i.e. 3β-acetoxy-12-hydroxyimino-18β-oleanan-28,13β-olide (substrate) and 3β-acetoxy-12-nitrile-12,13-seco-15(14?→?13)-abeoolean-14(27)-en-28,13β-olide and 3β-acetoxy-12-oxo-12a-aza-C-homoolean-13(18)-en-28-oic acid (Beckmann rearrangement reaction products) are described. Structural analysis revealed that the oxime group in the ring C in substrate molecule had an E-configuration. The nitrile product with retained lactone group was a result of major transformations within rings C and D of oleanane skeleton. In lactam product free carboxyl group and a double bond in ring D instead of lactone system were formed in Beckmann rearrangement reaction.
- Froelich, Anna,Bednarczyk-Cwynar, Barbara,Zaprutko, Lucjusz,Gzella, Andrzej
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p. 173 - 181
(2017/02/15)
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- DDQ-promoted dehydrogenation from natural rigid polycyclic acids or flexible alkyl acids to generate lactones by a radical ion mechanism
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A novel and facile DDQ-mediated dehydrogenation from natural rigid polycyclic acids or flexible alkyl acids to generate lactones is described. The formation of lactones proceeds by a radical ion mechanism, which has been established by DPPH?-mediated chemical identification, ESR spectroscopy and an enol intermediate trapping.
- Ding, Ye,Huang, Zhangjian,Yin, Jian,Lai, Yisheng,Zhang, Shibo,Zhang, Zhiguo,Fang, Lei,Peng, Sixun,Zhang, Yihua
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supporting information; experimental part
p. 9495 - 9497
(2011/10/31)
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- Synthesis and α-glucosidase inhibitory activity of oleanolic acid derivatives
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Glucosidations of oleanolic acid (1) and its dihydroxy-olide derivatives (2) were carried out to provide eight glycosides. All synthesized compounds were evaluated by in vitro α-glucosidase inhibitory activity assay. 3-Acetyl dihydroxy-olide oleanolic der
- Qian, Shan,Hai Li, Jiao,Wei Zhang, Yu,Chen, Xin,Wu, Yong
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scheme or table
p. 20 - 29
(2010/09/18)
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- Oxyfunctionalization products of terpenoids with dimethyldioxirane and their biological activity
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Oxyfunctionalization of the bioactive terpenoids, ursolic acid acetate (1), oleanolic acid acetate (5), lupeol acetate (12), and kaurenic acid (17), with dimethyldioxirane (DMDO) was investigated. Treatment of the terpenoids with DMDO under mild conditions afforded a variety of oxidation and oxydegradation products to yield naturally occurring and/or novel compounds in one step. After chromatographic separation, the structures of the individual isolated products were determined using spectroscopic methods including several homonuclear ( 1H-1H) and heteronuclear (1H-13C) shift-correlated 2D-NMR techniques. The inhibitory activity of the terpenoid derivatives against α-glucosidase was investigated and compounds 1, 3, 7, and 9 were found to exhibit potent activity.
- Ogawa, Shoujiro,Hosoi, Keiji,Ikeda, Noriaki,Makino, Mitsuko,Fujimoto, Yasuo,Iida, Takashi
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p. 247 - 250
(2007/10/03)
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- Partial synthesis of C-ring derivatives from oleanolic and maslinic acids. Formation of several triene systems by chemical and photochemical isomerization processes
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Some triterpenic compounds modified in C-ring were semi-synthesised from oleanolic acid contained in the solid waste of olive-oil pressing. The corresponding esters of oleanolic and maslinic acids rendered products with a diene system, which led to oleantrienes resembling previtamin D2 by an electrocyclic reaction. Chemical and photochemical isomerization of these compounds yielded two different trienes with similar structure to tachysterol and vitamin D2.
- García-Granados, Andrés,López, Pilar E.,Melguizo, Enrique,Parra, Andrés,Simeó, Yolanda
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p. 1491 - 1503
(2007/10/03)
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- OXIDATIVE TRANSFORMATIONS OF TRITERPENOIDS OF THE URSANE AND OLEANANE SKELETA WITH HYDROGEN PEROXIDE. INTRODUCTION OF 11,12-DOUBLE BOND AND 13(28)OXIDE MOIETY IN THE URSANE SYSTEM
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Treatment of oleanolic acid acetate (1b) with H2O2 in boiling HOAc gave the epoxy-γ-lactone 2b and the 12-hydroxy-γ-lactone 3b.The total absence of the 12-ketodihydro acid 4b among the oxidation products of 1b has been rationalised.The results of this reaction with several isomeric pairs of triterpenoids of the ursane and oleanane skeleta bearing functional groups at C-17 other than a carboxyl group show that for any appreciable oxidation involving the intermediacy of a 12β,13β-epoxide 6a or 6b, the 17-carboxyl group is an essential requirement.An intramolecular epoxidation of 12,13-double bond of 1a and 1b by 17-percarboxy acid formed in situ has been envisaged.The reactions aiming at introducing 11,12-double bond and 13(28)-oxide moiety in the ursane system are described.The desired compound 2c was obtained by treatment of the triol 1p with TsOH.With H2O2/TsOH, 1p, however, gave besides 2c, the rearranged product 8a.The difference in the chemical behaviour of 1p and 1q has been explained.Treatment of 2e with H2O2 in boiling HOAc gave the epoxide 2f.The mechanism of formation of 2a and 2b is discussed in the light of this observation.
- Majumder, P. L.,Bagchi, A.
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p. 649 - 656
(2007/10/02)
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- Triterpenoids of the Bark of Pieris japonica D. Don (Japenese Name: Asebi). II. 13C Nuclear Magnetic Resonance of the γ-Lactones of Ursane- and Oleane-type Triterpenes
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Eight triterpenoids and a sterol were isolated from the bark of Pieris japonica D.Don (Japenese name: asebi, Ericaceae) and have been elucidated as 3β-acetoxyurs-11-en-28,13-olide, 3β-acetoxy-12α-hydroxyolean-28,13-olide, 3β-acetoxy-28-hydroxyurs-12-ene, 3β,28-dihydroxyurs-12-ene, 3β-acetoxyurs-12-en-28-al, taraxeryl-acetate, taraxerol, taraxerone and β-sitosterone by a combination of chemical and spectroscopic studies. 13C Nuclear magnetic resonance spectral analysis of several γ-lactones of the ursane and oleanane series was undertaken, and all the carbons were assigned by means of single frequency off-resonance and selective decoupling methods and by comparison of the signals with those of methyl esters of acetyl ursolic acid and acetyl oleanolic acid.Keywords - Pieris japonica; bark; triterpenoid; ursane-type γ-lactone; oleanane-type γ-lactone; 1H-NMR; 13C-NMR
- Katai, Masaaki,Terai, Tadamasa,Meguri, Haruo
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p. 1567 - 1571
(2007/10/02)
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