1896-72-6Relevant academic research and scientific papers
Different pathways for the deoxygenation of the A-ring of natural triterpene compounds
Parra, Andres,Lopez, Pilar E.,Garcia-Granados, Andres
scheme or table, p. 177 - 196 (2010/05/18)
Some deoxygenation pathways were tested to remove the hydroxyl groups of the natural triterpenes oleanolic acid and maslinic acid to obtain a practical starting material for the semisynthesis of other interesting organic synthons. Different deoxygenation processes were carried out starting from these triterpenic acids or from several derivatives such as methyl esters and epoxy derivatives. The hydroxyl groups were transformed into some intermediate compounds including xanthyl, thiocarbonyl or tosyl derivatives. The opening of the oxirane ring between C-2 and C-3 was also achieved through different methods using deoxygenating reagents such as Me3SiCl/NaI, WCl 4/n-BuLi and Cp2TiCl.
Semi-synthesis of Triterpene A-Ring Derivatives from Oleanolic and Maslinic Acids. Theoretical and Experimental 13C Chemical Shifts
Garcia-Granados, Andres,Duenas, Jose,Moliz, Juan N.,Parra, Andres,Perez, Felipe L.,Dobado, J. A.,Molina, Jose
, p. 326 - 339 (2007/10/03)
Oleanolic and maslinic acids were isolated from solid waste from olive oil and several derivatives were semi-synthesised using typical reaction procedures. Rearrangements of methyl oleanate by mesylation or treatment with phosphorus pentachloride were accomplished. Six rearranged products were obtained from these reactions, three of which were 3(4) -> 5-abeo compounds formed by A-ring contraction of the oleanene skeleton. Experimental 13C NMR chemical shifts for 21 compounds are given and a discussion of the substituent effects on their 13C shieldings are also included. Morover, theoretical 13C NMR chemical shifts, with the GIAO method calculated at the MM+ geometries using the B3LYP/6-31G* level, showed good agreement with the experimental, allowing a correct assignment for the experimental shifts.
