Synthesis of Biologically Active Betulin-based Triterpene Compounds
Paper describes the developed by authors the novel methods of triterpene compounds synthesis from biologically active betulin, which have prospects for the design the new drugs. The improved method of betulinic acid synthesis by sodium betulonate reduction by BH4 in water medium is developed. The method of betulonic acid reduction to betulinic acid at conditions of phase-transfer catalysis was suggested which makes it possible to increase the betulinic acid yield up to 99 %. With the use of carbodiimide methods the next derivatives of betulinic acid were synthesized: cyclohexyl amide (yield 89 %), propyl amide (yield 84 %), tretbuthyl ether of valine (yield 83 %), tretbythyl ether of tyrosine (yield 84 %). The new one-step methods of synthesis of betulin diacetate by acetilation of outer bark and allobetuline synthesis by boiling in toluene or p-xylene of outer birch bark impregnated by sulphonic or ortophosphoric acids were developed.