Reaction of 2-bromo-3-keto triterpenoids: Deoxygenation and simultaneous debromination by Huang-Minion reduction condition
On heating 2α-bromo/2,2-dibromo lupanone (1/1a) and 2α-bromo/4α-bromo friedelin (2/2a) with diethylene glycol and hydrazine hydrate (Huang-Minlon modified Wolff-Kishner reaction) under reflux produced lupane (3) and- friedelane (4), respectively.
Ghosh, Pranab,Chakraborty, Prasanta
p. 519 - 524
(2013/11/06)
Studies on reaction of 2-bromo-3-ketotriterpenoids: Part IV - Debromination and dehydrobromination of 2α-bromo and 2,2-dibromo derivatives of lupanone and methyl dihydrobetulonate
2α-bromolupanone/methyl 2α-dibromodihydrobetulonate (1/1') and 2,2-dibromolupanone/methyl 2,2-dibromodihydrobetulonate (2/2') on refluxing with dimethylaniline (DMA) for 6 hr afford lupanone/methyl dihydrobetulonate (3/3') whereas 6 hr reflux of 1/1' and 2/2' with LiBr in dimethylformamide (DMF) furnish lup-1(2)-en-3-one/28-carbomethoxylup-1(2)-en-3-one (4/4') and 2-bromolup-1(2)-en-3-one/2-bromo-28-carbomethoxylup-1(2)-en-3-one (5/5'), respectively.On the other hand Wolff-Kishner reduction of 1/2 results in the formation of lupane (6).
Pradhan, Bhim Prasad,Ghosh, Pranab
p. 73 - 75
(2007/10/02)
The synthesis of nor- and bisnorlupanes
In course of our studies on geochemical biomarkers we required a series of lupane standards.We report here an efficient synthesis of lupane (1) in three steps from betulin (3) in an overall yield of 47.2 percent. 17β(H)-28-Norlupane (2) was obtained in 90
Wahhab, Amal,Ottosen, Margaret,Bachelor, Frank W.
p. 570 - 577
(2007/10/02)
HOMOGENEOUS HYDROGENATION AND DEUTERATION OF PENTACYCLIC TRITERPENOIDS: DOUBLE BONDS IN SIDE-CHAINS
The reduction of terminal double bonds in the side chains on the rings A and E of pentacyclic triterpenoids by means of tris(triphenylphosphine)rhodium chloride permits selective reduction of dienes and labelling with deuterium with a low scattering.The effect of the amount of the catalyst and the solvent used on the rate of reduction was studied in the case of 3β,28-diacetylbetulin.