Primary and secondary triterpene alcohols were acetylated for the first time using tetraacetylglycoluril (TAGU). Cholesterol, allobetulin, and betulin acetates were obtained in high yields. The acetylation used p-TsOH or TFA in refluxing CHCl3. TFA was found to be an effective acetylation catalyst.
Bismuth triflate-catalyzed Wagner-Meerwein rearrangement in terpenes. Application to the synthesis of the 18α-oleanane core and A-neo-18α-oleanene compounds from lupanes
作者:Jorge A. R. Salvador、Rui M. A. Pinto、Rita C. Santos、Christophe Le Roux、Ana Matos Beja、José A. Paixão
DOI:10.1039/b814448f
日期:——
catalysts for the Wagner-Meerwein rearrangement of lupane derivatives with expansion of ring E and formation of an additional O-containing ring is reported. This process has also been extended to other terpenes, such as the sesquiterpene (−)-caryophyllene oxide. When the reaction was performed with oleanonic acid, 28,13β-lactonization occurred, without Wagner-Meerwein rearrangement. Under more vigorous reaction
Synthesis of 19-(2,6-Dimethylpyrid-4-yl)-20,29,30-trinorlupanes
作者:A. N. Antimonova、N. I. Petrenko、M. M. Shakirov、E. E. Shul’ts
DOI:10.1007/s10600-014-0938-4
日期:2014.5
19-(2,6-Dimethylpyrid-4-yl)-20,29,30-trinorlupanes in addition to triterpenoid derivatives condensed in ring A of the pyran-4-one ring were synthesized for the first time from betulin, betulin diacetate, and methyl esters of 3-acetylbetulinic and betulonic acids.
3-O-substituted allobetulin saponins. This unprecedented migration of the sugar part is driven by the Wagner-Meerwein rearrangement of the betulin core. According to our mechanistic studies an oxocarbenium ion released during the rearrangement reacts with the free 3-OH group of the triterpene affording the final allobetulin saponin. Migration rate depends on the size and configuration of the sugar moiety