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Triterpene bidesmosides are considered as highly cytotoxic saponins, usually less toxic against normal cells than monodesmosides, and less haemolytic. Biological activity of the betulin-type bidesmosides, rarely found in Nature, and seldom prepared due to serious synthetic problems, is poorly recognized. We report herein a protocol for the preparation of disubstituted lupane saponins (betulin bidesmosides) by treatment of their benzoates with potassium carbonate in dichloromethane / methanol solution. Cytotoxicity of all compounds was tested in vitro for a series of cancer cell lines, as well as normal human skin BJ fibroblasts. Presence of l -rhamnose moiety is crucial for cytotoxicity of betulin bidesmosides. On the other hand, l -arabinose fragment connected to lupane C-3 carbon atom significantly decreases activity. Presented results clearly show that betulin bidesmosides have significant clinical potential as anticancer agents.

A concise synthesis of 28a-homo-28a-thiolupane triterpenes and the corresponding saponins containing D-mannose, D-idose, L-arabinose and L-rhamnose moieties was elaborated. New triterpenes were obtained from readily available 3-O-allylbetulinal by elongation of the carbon chain by Wittig reaction, followed by hydrolysis of the enol ether, reduction of the elongated aldehyde and nucleophilic substitution of the corresponding mesylate with thiocyanate ion. Saponins were obtained by glycosylation of triterpenes with classical Schmidt donors. The cytotoxic activities of the new homothiolupane compounds were evaluated in vitro, revealing that some triterpenes and the corresponding saponins exhibited interesting cytotoxic activity profiles against human cancer cell lines. An unexpected influence of the allyl protecting group on the cytotoxicity of homothiobetulin derivatives was revealed. These results open the way to the synthesis of various lupane-type derivatives containing sulfur in the lupane side chain as potential anticancer compounds.

A concise synthesis of 28a-homolupane triterpenes and the corresponding saponins containing d -mannose, d -idose, d -arabinose, and l -rhamnose moieties was elaborated. The overall synthesis of the new triterpenes involved three linear steps starting from readily available 3-O-acetyl-betulinal: elongation of the carbon chain by Wittig reaction followed by enol ether hydrolysis and reduction (or oxidation) of the elongated aldehyde. Saponins were obtained by glycosylation of triterpenes with classical Schmidt donors. Cytotoxic activities of new lupane and homolupane compounds were evaluated in vitro. Several triterpenes and the corresponding saponins exhibited an interesting cytotoxic activity profile against human cancer cell lines. Influence of the side-chain structure and substituents on the cytotoxicity of betulin and homobetulin derivatives was investigated. These results open the way to the synthesis of various lupane-type triterpene and saponin derivatives as potential anticancer compounds.

A concise synthesis of lupane triterpenes with an elongated carbon chain at the C-28 position, as well as saponins containing d -mannose, l -arabinose, and l -rhamnose moieties at the C-3 position is described. The overall synthesis of the new triterpenes involved seven linear steps starting from natural betulin: selective protection of a hydroxyl group, oxidation, elongation of the carbon chain by Grignard reaction, and deoxygenation. O-Glycosides were obtained by glycosylation of triterpenes with classical Schmidt's donors. Additionally, all new compounds were evaluated in vitro for their cytotoxic activities. Several triterpenes and the corresponding saponins exhibited an interesting cytotoxic activity profile against human cancer cell lines. The therapeutical index of active triterpenes is very high, since almost none of them were cytotoxic for normal BJ fibroblasts. These results open the way to the synthesis of various lupane-type saponin derivatives as potentially bioactive compounds.

A series of lupane-type saponins bearing OSW-1 disaccharide unit as well as its regio- and stereoisomers were prepared and used for the structure-activity relationships (SAR) study. Unexpected preference for 1→4-linked regioisomers and an unusual inversion of the conformation of the sugar rings were noted. Cytotoxic activity of new lupane compounds was evaluated in vitro and revealed that some saponins exhibited an interesting bioactivity profile against human cancer cell lines. Influence of the protecting groups on the cytotoxicity was investigated. These results open the way to the synthesis of various lupane-type triterpene and saponin derivatives as potential anticancer compounds.