Cellular screening of various synthetic triterpenoid compounds formally derived from lupane has identified a number of analogues as potential anticancer drug candidates. Here we describe the synthesis and structure-activity relationships of betulin and betulinic acid derivatives containing an E-ring modified with different oxygen functions. Thus compounds containing the lup-18-en-21-one, lup-18-ene-21,22-dione, 18,19-secolupane, and the highly oxygenated 18,19-secolupane systems, as well as des-E-lupane derivatives, were prepared from the readily available natural pentacyclic triterpene betulin using oxidative procedures. These compounds were named betulinines. We demonstrate that only selected compounds, particularly those containing a lupane E-ring-derived unsaturated ketone or diketone function, possessed in vitro cytotoxic activity against tumor cell lines, suggesting a structure-activity relationship.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Oxidation of 19β,28-epoxy-18α-oleanan-3-one (1) with chromium(VI) oxide in acetic acid leads to the formation of the 1β,3β;19β,28-diepoxy-3-hydroxy-1,2-seco-18α-oleanano- 2,1α-lactone (2). Its structure follows from spectral data, molecular modelling. Lactone 2 was converted to its acetate 3, methyl 19β,28-epoxy-1,3-dioxo-1,2-seco-18α-oleanan-2-oate (4) and to the stereoisomers at C(3) of methyl 1,3;19β,28-diepoxy-1-oxo-1,2-seco-18α-oleanan-2-oate (6 and 7) and dimethyl 19β,28-epoxy-3-hydroxy-1,2-seco-18α-oleanan-1,2-dioate (8 and 9). Lactone 2 reacts slowly with diazomethane which is indicative for its equilibrium with a small amount of free acid. Alkaline hydrolysis of compound 2 leads to compounds 8 and 9; the reaction involves hydride transfer of a Cannizzaro reaction type. A high rotational barriers were found in compounds 8 and 9. A combination of NMR methods and molecular modelling revealed that most sterically hindered bond in both compounds is the C(1)-C(10) single bond.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Depending on the conditions and the acid employed, 18β,19β-epoxy-28-hydroxy- 21-oxolupan-3β-yl acetate ( 2a ) and 18β,19β-epoxy-21-oxolupane-3β,28-diyl diacetate ( 2b ) on treatment with acid gave three types of products: (i) 28-nor derivatives: 21-oxo-28-norlupa-16,18-dien-3β-yl acetate ( 6 ), 19β-hydroxy-21-oxo-28-norlup-17-en-3β-yl acetate ( 7 ) and 17ξ-hydroxy-21-oxo-28-norlup-18-en-3β-yl acetate ( 8 ), (ii) lupa-12,18-dien-21-ones 4a and 4b , and (iii) 22β-substituted lup-18-en-21-one derivatives of the type 5 . The formation of 22β-substituted derivatives of the type 5 probably proceeds in the enol form of epoxy ketone 2 . Opening of the epoxide ring with shift of the double bond to position 19(21) and attack by nucleophilic species at C-22 followed by elimination of water and re-formation of the 22-oxo group leads to derivatives of the type 5 .

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A series of 3- and 28-glucosides and glucosyl esters of betulinic acid (1a), 28-hydroxy-3,4-secolupa-4(23),20(29)-dien-3-oic acid (22a), dimethyl ester of 28-hydroxy-2,3-secolup-20(29)-en-2,3-dioic acid (43a), their 20(29)-dihydro derivatives (1b, 22b, 43b) and several other triterpenes of the lupane (12a, 12b) and 3,4-secolupane series (18a, 18b, 32a) has been prepared by reaction of tetra-O-acetyl-α-D-glucopyranosyl bromide in acetonitrile in the presence of mercury(II) cyanide and subsequent deacetylation of the obtained tetra-O-acetyl-β-D-glucopyranosyl derivatives. In several cases attempted glucosylation in the presence of silver silicate afforded predominantly the corresponding 1,2-orthoacetates of α-D-glucopyranose.

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1 H NMR, 13 C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1 H and 13 C NMR spectra are discussed.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The triterpenoid α-diketone with oxabicyclo[2.2.2]octane system in the ring E (3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (I)) gives isopropylidenedioxy derivative II and dimeric compounds V and IX when submitted to chromatography on silica gel in the presence of acetone. Compounds V and IX were reduced with hydride to hydroxy derivatives VI, X, and XI; on reaction with diazomethane they gave dimeric compounds with spiroepoxide group at the position 21 (compound VII) or 22 (compound XII) which reacted further with diazomethane to give monomeric spiroepoxides VIII, XIII, and XIV. The structure of the compounds obtained was derived from their 1H and 13C NMR, IR, and FAB mass spectra.

Triazene derivatives of estrone and estradiol in positions 2 and 4 were prepared. Their reaction with sodium iodide in an acid medium afforded the corresponding iodo derivatives. The H-1 NMR, C-13 NMR and mass spectra of the compounds prepared are discussed.

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A series of epimeric pairs of 20R and 20S acetylamino derivatives VIII-XI have been prepared by reduction and subsequent acetylation of the oximes I, III, IV and VI. Their absolute configuration at C-20 (20R and 20S for the series a and b, respectively) has been suggested on the basis of their physical and spectral properties. The correctness of this assignment was confirmed by the synthesis of the acetylamino derivatives Xa and Xb from the acids XIIa and XIIb, respectively, with known configuration at C-20.

The structure of anhydrobetulin II and its derivatives, I, III and IV has been solved using H-1 and C-13 NMR spectra, mass spectra and chemical transformations. It has been proven that in addition reactions the trisubstituted double bond is attacked selectively from the alpha-side under formation of D/E cis-annelated derivatives VIII, X and XI. The 22-oxo derivative XIII exhibits an anomalous Cotton effect and, in contrast to its saturated analogue XXVII, it is not epimerized in alkaline medium. Trinordiketone XXI easily epimerizes to a mixture in which the 17-beta-H-epimer XXIb predominates, trinorketone XXIV is stable only if the annelation of rings D and E is trans. These differences are explained in terms of steric interactions of substituents in position 19. The steric course of reduction of ketones XIII and XXIV with sodium borohydride is described.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The structure of anhydrobetulin II and its derivatives I, III and IV has been solved using 1H and 13C NMR spectra, mass spectra and chemical transformations. It has been proven that in addition reactions the trisubstituted double bond is attacked selectively from the α-side under formation of D/E cis-annelated derivatives VIII, X and XI. The 22-oxo derivative XIII exhibits an anomalous Cotton effect and, in contrast to its saturated analogue XXVII,it is not epimerized in alkaline medium. Trinordiketone XXI easily epimerizes to a mixture in which the 17βH-epimer XXIb predominates, trinorketone XXIV is stable only if the annelation of rings D and E is trans. These differences are explained in terms of steric interactions of substituents in position 19. The steric course of reduction of ketones XIII and XXIV with sodium borohydride is described.