Synthesis of pyrrol-2-yl- and pyrazol-4-ylmethylidene derivatives of betulin and allobetulin

Abstract

Aldol-crotonic condensation of allobetulone and betulonic aldehyde with N-substituted pyrrole-2and pyrazole-4-carbaldehydes afforded a series of new α,β-unsaturated ketones of lupane series. Their reduction provided 2-ylidene derivatives of allobetulin and betulin, potential chiral components of liquid crystal materials. Structures of 1were established by X-ray diffraction (XRD) study .

The synthesis of α,β-unsaturated 18αH,19βH-ursane methyl ketones

“…Here we additionally confirmed the structure of aldehyde 4 by X-ray diffraction analysis (Figure 1). According to the literature 14 , alkaline hydrolysis of 3,28-diacylderivatives of 30-nitril-, or 30-carboxy-, or 30-carbomethoxy-, or 30-hydroxyheterobetulin leds to the formation of the tetrahydrofuran cycle bonded to ring E via the C17 and C21 carbon atoms. When α,β-unsaturated aldehyde 4 was boiled in an alcoholic solution of KOH, the 21β,28-epoxy aldehyde 5 was also formed.…”

“…The interest indicated by medicinal chemists in triterpenic carbon scaffolds is caused by attractive opportunities of improving physicochemical, pharmacokinetic, and pharmacodynamic properties of triterpenoids through their simple structural transformations, modifications of functional groups or the introduction of new reaction centers [7][8][9][10] . Considering that triterpenic oxo-derivatives are favorable objects for various chemical modifications, including the so-called aldol condensation forming new carbon-carbon bonds 11 , triterpenic α,β-unsaturated ketones were synthesized by a simple reaction of some aromatic and heterocyclic aldehydes as carbonyl component with triterpenic 3-ketones as a methylene component 7,[12][13][14][15][16] , while lupane 28-aldehyde was used as a carbonyl reactant in condensation with acetophenone 17 . The introduction of α,β-unsaturated oxo-fragment into triterpenic structures frequently enables to enhance synthetic 18,19 and biological 20,21 potentials of polycyclic triterpenoids.…”

Synthesis and Characterization of Novel Bio-Chiral Dopants Obtained from Bio-Betulin Produced by a Fermentation Process

“…Betulin itself or its simple ester derivatives, to our knowledge, have not been previously examined as twist agents. However, betulin derivatives such as betulinic aldehyde [10] and allobetulin or allobetulone [11,12] have been examined in different liquid crystal-related applications.…”