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Treatment of betulin-type saponins, in which the sugar moiety is connected at the 28-position, with TMSOTf affords 3-O-substituted allobetulin saponins. This unprecedented migration of the sugar part is driven by the Wagner-Meerwein rearrangement of the betulin core. According to our mechanistic studies an oxocarbenium ion released during the rearrangement reacts with the free 3-OH group of the triterpene affording the final allobetulin saponin. Migration rate depends on the size and configuration of the sugar moiety.

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 practical method for the preparation of benzoyl protected allyl and benzyl α-D-idopyranosides, and D-idopyranosyl trichloroacetimidate, from 1,2,3,4,6-penta-O-acetyl-α-D-idopyranose, is described. All derivatives can be prepared on a multigram scale and require only simple chromatographic purification. A concise synthesis of lupane triterpenes bearing an unusual D-idopyranoside fragment is described. All new compounds were evaluated in vitro for their cytotoxic activities. Novel saponins exhibited interesting cytotoxic activity in the micromolar range against human cancer cell lines including T-lymphoblastic leukemia CEM, breast adenocarcinoma MCF7, and cervical carcinoma HeLa, but also against normal human fibroblasts BJ.

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.

A series of new (3,4) β-methylenecepham and carbacepham analogues were synthesised as potential antibacterial agents. The key step of the synthesis included presumed generation of the carbene species from the oxalimide substrate effected by triethylphosphite and its intramolecular addition to the double bond. The stereochemistry of the tricyclic system has been elucidated by NMR and X-ray crystallography. In preliminary screening, two of the synthesised compounds exhibited modest antibacterial activity at 1.5–2.0 mg/mL against a number of bacterial strains.

Reactions of hydrosilanes with 1-hexyne catalyzed by Co 2 Rh 2 (CO) 12 , Rh 4 (CO) 12 , ( t BuNC) 4 RhCo(CO) 4 , and Rh(acac)(CO) 2 at 25°C and atmospheric pressure to 10 atm of carbon monoxide give (Z)-1-silyl-2-formyl-1-hexenes ( 1 ), which are the products of “silylformylation”, and/or ( E )-1-silyl-1-hexenes ( 2 ). The ratio of silylformylation vs. hydrosilylation products depends on the electronic nature of hydrosilane used, e.g., PhMe 2 SiH gives 1 almost exclusively whereas (MeO) 3 SiH favors the formation of 2 . When trialkylsilanes such as Et 3 SiH and EtMe 2 SiH are used, the reaction catalyzed by Co 2 Rh 2 (CO) 12 or ( t BuNC) 4 RhCo(CO) 4 gives 2,5-bis(n-butyl)-3-silylcyclopent-2-en-1-one ( 3 ) as a major product, which is a unique silylcarbocyclization product. Mechanism of the formation of 3 is discussed on the basis of deuterium-labeling experiments. Chemoselective silylformylations of alkenynes, a dialkyne, and an alkynyl nitrile proceed in high yields in which alkene and nitrile functionalities are inert for the reaction. Silylformylation is successfully applied to the syntheses of pyrrolizidine alkaloids, (±)-isoretronecanol and (±)-trachelanthamidine, from 5-ethynyl-2-pyrrolidinone ( 6 ) in combination with amidocarbonylation.

Reactions of hydrosilanes with 1-hexyne catalyzed by Co 2 Rh 2 (CO) 12 , Rh 4 (CO) 12 , ( t BuNC) 4 RhCo(CO) 4 , and Rh(acac)(CO) 2 at 25°C and atmospheric pressure to 10 atm of carbon monoxide give (Z)-1-silyl-2-formyl-1-hexenes ( 1 ), which are the products of “silylformylation”, and/or ( E )-1-silyl-1-hexenes ( 2 ). The ratio of silylformylation vs. hydrosilylation products depends on the electronic nature of hydrosilane used, e.g., PhMe 2 SiH gives 1 almost exclusively whereas (MeO) 3 SiH favors the formation of 2 . When trialkylsilanes such as Et 3 SiH and EtMe 2 SiH are used, the reaction catalyzed by Co 2 Rh 2 (CO) 12 or ( t BuNC) 4 RhCo(CO) 4 gives 2,5-bis(n-butyl)-3-silylcyclopent-2-en-1-one ( 3 ) as a major product, which is a unique silylcarbocyclization product. Mechanism of the formation of 3 is discussed on the basis of deuterium-labeling experiments. Chemoselective silylformylations of alkenynes, a dialkyne, and an alkynyl nitrile proceed in high yields in which alkene and nitrile functionalities are inert for the reaction. Silylformylation is successfully applied to the syntheses of pyrrolizidine alkaloids, (±)-isoretronecanol and (±)-trachelanthamidine, from 5-ethynyl-2-pyrrolidinone ( 6 ) in combination with amidocarbonylation.

The reactions of hydrosilane and/or alkyne as well as isonitriles with rhodium and rhodium cobalt mixed metal carbonyl clusters, e.g., Rh4(CO)12 and Co2Rh2(CO)12, are studied. Novel mixed metal complexes, e.g., CoRh(CO)5 (HC≡CBu n ), (R3Si)2Rh(CO) n Co(CO)4, Rh(R−N≡C)4Co(CO)4, Co2Rh2(CO)10(HC≡CR), and Co2Rh2(CO)9(HC≡CBu n ), are synthesized and identified. The catalytic activities of these rhodium and rhodium-cobalt mixed metal complexes are examined in hydrosilyation, silylformylation, and novel silylcarbocyclization reactions. Possible mechanisms for these reactions are proposed and discussed.

It is well-established that when polymer size exceeds the size of a confining space, the equilibrium partition of polymer between the confined space and the bulk solution is zero. Surprisingly, we found that the long water-soluble polymers with a small hydrophobic group can be efficiently trapped inside the water channels (nanopores) of the hexagonal phase of non-ionic surfactant.

The efficacy of a series of dinitroaniline herbicide derivatives for the treatment of Cryptosporidium parvum infections has been studied. The lead compounds oryzalin (compound 1) and trifluralin (compound 2) have low water solubility (C. parvum assays, a result in direct contrast to earlier work with Leishmania . Enhanced water solubility alone did not overcome the drug availability problem; however, several candidates with similar activities but with toxicities lower than those of the lead compounds were produced.

The catalytic systems containing the zerovalent tungsten complexes W(CO)6 and (arene)W(CO)3, RAICl2 (R = Me,Et) and molecular oxygen have been investigated in the metathesis of internal and terminal olefins. Besides metathesis, double bond migrations have been found to occur, especially when a terminal olefin was employed as the substrate. Some factors affecting the catalysts' activity and the lifetime of the active centres are described.

Reaction of tetralin in the presence of AlCl 3 and its modifications has been reinvestigated and the products identified. 5- and 6-(1-phenylbutyl) tetralins are the primary products, which subsequently form partly hydrogenated tricyclic aromatic compounds and benzene. Further reactions produce ethylbenzene, n-butylbenzene, ethyltetralins and n-butyltetralins. A catalytic system containing AlCl 3 and hydrated salts (CH 3 COONa·3H 2 O and FeCl 3 ·2H 2 O) has been found to convert tetralin to 5- and 6-(1-phenylbutyl)tetralins with high selectivity.

Synthese selective de l'acide N-phenyl formohydroxamique, par reaction du formaldehyde avec le nitrosobenzene en presence de sels de Co(II) dans differents solvants organiques (acetone, acetonitrile, methanol, nitromethane)