Rinat R. Gubaidullin

Synthesis and activity of new triphenylphosphonium derivatives of betulin and betulinic acid against Schistosoma mansoni in vitro and in vivo.

We studied the antischistosomal activity of betulin, betulinic acid and its 9 triphenylphosphonium derivatives characterized by a covalently linkage of the hydrophobic fragment of triterpenoid at C(2)- or C(30)-position with the triphenylphosphonium moiety via a hydrocarbon bridge. The triphenylphosphonium salts showed in vitro antischistosomal activity against newly transformed schistosomula (NTS) and adult worms of Schistosoma mansoni at low micromolar concentrations. In contrast betulin and betulinic acid were inactive against NTS and adult S. mansoni. Of the 9 triphenylphosphonium derivatives tested, the allyl salts 10 (IC50 of 0.76 μg/mL) and 11 (IC50 of 0.64 μg/mL) demonstrated the highest antischistosomal activity against adult S. mansoni. Low worm burden reductions of 22% were observed in vivo for these two compounds. In conclusion, triphenylphosphonium derivatives were obtained from available natural betulin by simple transformations, rendering it practical and useful for large scale application. However, further structural modifications are necessary to translate the promising antischistosomal in vitro activities into in vivo.

Synthesis of lupane triterpenoids with triphenylphosphonium substituents and studies of their antitumor activity

New derivatives of lupane triterpenoids, viz., 20,29-dihydrobetulinic and 3-epi-20,29-dihydrobetulinic acid derivatives containing triphenylphosphonium fragments as substituents were synthesized. These compound considerably exceed betulinic acid in antitumor activity.

Synthesis of tetrasubstituted furans by multicomponent reaction of alkynes with dichloro(ethyl)aluminum and carboxylic acid esters in the presence of Cp2TiCl2

A one-pot procedure has been developed for the synthesis of 3,4-dialkyl-2,5-dicycloalkyl(aryl, hetaryl)furans in 38–82% yield by reaction of symmetrical alkynes with cycloalkane(arene, hetarene)carboxylic acid esters and EtAlCl2 in the presence of Cp2TiCl2 as catalyst.

Triphenylphosphonium cations of betulinic acid derivatives: synthesis and antitumor activity

A series of lupane triterpenoid conjugates with the triphenylphosphonium cation, in which the terpenoid molecules are linked to one or two triphenylphosphonium moieties at the С-2, С-28, or С-30 positions by carbon–carbon or ester bonds, have been designed and synthesized as potential anti-cancer agents. The pharmacological results showed that all of the prepared triphenylphosphonium salts displayed considerable antitumor activities against the tested cancer murine tumor (Ehrlich ascites carcinoma, (Р-815), and human tumor (MCF-7) (IC50 < 2 μg/mL)) cell lines. The presence of the triphenylphosphonium cation in the triterpenoid conjugates markedly enhanced the cytotoxic action as compared to the parent compound (betulinic acid) (IC50 24.7 μg/mL for Ehrlich cells and 18.7 μg/mL for Р-815 cells), while the correlation between the cytotoxic activity and the chemical structure of phosphonium salts was not observed.