Oxidative transformations of cembrane diterpenoids I. Oxidation of cembrene with chromium trioxide

Summary 1. The oxidation of cembrene with chromium trioxide in aqueous sulfuric acid (the Jones reagent) and in aqueous acetone has given norcembra-2,7,11-trien-4-one, norsolanadione, (3E, 8E)-5-isopropyl-8-methyltrideca-3,8-diene-2,12-dione, and five new compounds the structures of which have been established on the basis of their spectra.2. Oxidation with chromium trioxide in aqueous acetone, in contrast to oxidation with the Jones reagent, takes place stereospecifically—the C₁₁-C₁₂ double bond of cembrene is not affected.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 313–320, May–June, 1976.     

Oxidative transformations of cembrane diterpenoids. II. Cembra-2,7,11-triene-4,5-diols

Summary 1. The oxidation of cembrene with chromium trioxide in aqueous acetone forms, together with other compounds, the products of its hydroxylation at the C₄ double bond — cembra-2,-7,11-triene-4,5-diols epimeric at the C₄ double bond.2. On the basis of chemical and spectral characteristics, it has been established that these diols have the 4S, 5R and 4R, 5R configurations, respectively.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR, and Novosibirsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–59, January–February, 1977.     

Stereoselectivity of the exhaustive epoxidation of cembrene by peracetic acid. Crystalline and molecular structure of triepoxycembrene

The epoxidation of the diterpene hydrocarbon cembrene with peracetic acid in methylene chloride in the presence of sodium bicarbonate forms a single triepoxide — 4,5:7,8:11,12-triepoxycembrene with the 4S, 5R, 7S, 8S, 11S, 12S configuration of the asymmetric centers. The structure and stereochemistry of triepoxycembrene have been determined with the aid of x-ray structural analysis.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 174–178, March–April, 1981.     

Photosensitized oxidation of isocembrol. VII. Products of reaction at the C11 double bond

It has been established that in the photooxidation of isocembrol, in addition to other compounds, five products of oxidation at the C₁₁ double bond are formed, and their structures and stereochemistry have been established by chemical transformations and physicochemical methods. In the stereochemical respect, the photooxidation of isocembrol at the C₁₁ double bond is similar to its epoxidation at the same bond.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 48–56, January–February, 1984.     

Oxidative transformations of cembrane diterpenoids. VI. Epoxidation of isocembrol

The stereochemistry of the epoxidation of the diterpene alcohol isocembrol has been studied. The main direction of attack of peracids is the C₁₁ double bond of isocembrol, with the predominant formation of the 11S,12S-epoxide. The ratio of the monoepoxyisocembrols does not change appreciably with a variation in the temperature of the reaction or in the peracid used. 11S,12S-Epoxyisocembrol has been isolated as a natural product from the oleoresin of the Siberian stone pine.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 581–587, September–October, 1983.     

Oxidative transformations of cembrane diterpenoids IV. Photooxidation of cembrene

The photooxidation of cembrene by singlet oxygen is a stereoselective reaction and it is stereochemically similar to the epoxidation of cembrene by peracids. From the mixture of the photooxidation products of cembrene after its treatment with sodium tetrahydroborate four allyl alcohols have been isolated and the structures of two of them, previously undescribed, have been established on the basis of their spectral characteristics. The main component of these alcohols is cembra-2E, 4Z, 7E, 10E-tetraen-12S-ol.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 60–67, January–February, 1981.     

Oxidative transformations of cembrane diterpenoids I. Oxidation of cembrene with chromium trioxide

1. The oxidation of cembrene with chromium trioxide in aqueous sulfuric acid (the Jones reagent) and in aqueous acetone has given norcembra-2,7,11-trien-4-one, norsolanadione, (3E, 8E)-5-isopropyl-8-methyltrideca-3,8-diene-2,12-dione, and five new compounds the structures of which have been established on the basis of their spectra. 2. Oxidation with chromium trioxide in aqueous acetone, in contrast to oxidation with the Jones reagent, takes place stereospecifically—the C₁₁-C₁₂ double bond of cembrene is not affected.     

Composition of the neutral fraction of the resin ofPinus sibirica R. Mayr.

Summary 1. The high-boiling neutral fraction of the resin of the Siberian cedar contains abietinal, a diterpene diol C₂₀H₃₄O₂, and the diterpene alcohol cembrol C₂₀H₃₄O₂ which has a 14-membered ring and three double bonds; the dehydration of cembrol gives the diterpene hydrocarbon cembrene C₂₀H₃₂; the probable structure of cembrol is 14-isopropyl-3, 7, 11-trimethylcyclotetradeca-1, 3, 6-trien-11-ol.2. Besides the diterpene alcohols and abietinal, the high-boiling oxygen containing fraction of the cedar resin contains D--cadinol C₁₅H₂₆O and a lactone C₁₇H₂₆O₃.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 4, pp. 250–256, 1965     

Stereoselectivity of photo-oxidation at the C7 double bond of isocembrol and its derivatives

The products and stereochemistry of the photo-oxidation at the C₇ double bond of isocembrol and two of its derivatives have been investigated. The stereoselectivity of the transformations performed is discussed.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 437–444, July–August, 1984.     

Chemical transformations of lignin during the biodegradation and organosolv pulping of deciduous wood

The lignins from the liquors in the organosolv pulping of aspen wood treated with wood-destroying fungi have been investigated using quantitative¹H and¹³C NMR spectroscopy and exclusion liquid chromatography. It has been shown that the biodegradation of lignin takes place in different ways according to the complex of enzymes produced by the fungi. Phanerochaete sanguinea causes degradation through predominant cleavage at alkyl-phenyl bonds, and Trametes villosus at the C-C bonds of the aliphatic chain. In addition to degradation reactions, polymerization (condensation) reactions also take place with the appearance of new C_ar-O-C and C_ar-C bonds. It has been established that the biological pretreatment of aspen wood ensuring partial degradation of the lignin leads to its more ready extraction in the process of organosolv pulping.Wood Chemistry Division of the Irkutsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 603–610, July–August, 1995. Original article submitted May 23, 1994.     

Cyclization and rearrangements of diterpenoids. IX. Isomerization of (1R,2S,7S,10S,11R,12S,13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.01,10.02,7.011,13]pentadecane by fluorosulfonic acid

It has been shown that the opening of the cyclopropane ring in (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethylpentacyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane takes place under the action of fluorosulfonic acid at all three carbon-carbon bonds, but at low temperatures the main isomerization product is (1R, 2S, 7S, 10S, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-13-ol, and at the ordinary temperature the main products are (1R, 2S, 7S, 11S, 12R, 13R)-2,6,6,11,13-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadeca-9-ene and (1S, 2R, 11S, 12R, 15R)-2,7,7,11,15-pentamethyltetracyclo[10.2.1.0^2,11.0^3,8]pentadeca-3(8)-ene.Institute of Chemistry, Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 497–500, July–August, 1989.     

Fluoroindenes. 13. Transformations of polyfluorinated indenes and 1-alkylideneindans in the H2O2-HF-SbF5 system

The reaction of perfluorinated indene, 3-methylindene, and 1-methylene- and 1-ethylideneindans with hydrogen peroxide in the hydrogen fluoride—antimony pentafluoride medium takes place at the multiple bond of the substrate and leads to the oxo derivatives of indan. The process probably takes place through the electrophilic addition of HO⁺. The C=C bond in perfluoro-3-methylindenone is not affected. In this compound and also in perfluoro-2-indanone and perfluoro-1-methyl-2-indanone the carbonyl group is involved in reaction with hydrogen peroxide in the HF-SbF₅ system, and six-membered oxygen-containing heterocyclic compounds are formed.For Communication 12, see [1].Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1412–1419, June, 1992.     

Cyclization of cembrane diterpenoids. V. Selectivity of the formation of a product of the cyclization of cembrene under the action of N-bromosuccinimide, and the crystal structure of this product

Under the action of N-bromosuccinimide in aqueous acetone, cembrene has given a low yield of a cyclization product, the structure and stereochemistry of the molecule of which have been established by x-ray structural analysis. In contrast to the cyclization of cembrene under the action of formic acid, in the reaction under consideration a 1,5-hydride shift in the last stage dominates substantially over the splitting out of a proton from the methyl group at C-4.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 687–691, September–October, 1993.     

Synthesis of hexylthiols C6H13SH−1/1, 2, 3, 4−14C1/4/' /1-thiol[35S]/ and C6H13SH−2/1, 2, 3, 4−14C1/4/, /2-thiol[35S]/

A synthesis of¹⁴C and³⁵S double labelled hexylthiols: C₆H₁₃SH–1/1, 2, 3, 4–¹⁴C_1/4/, /1-thiol[³⁵S]/ and C₆H₁₃SSH–2/1, 2, 3, 4–¹⁴C_1/4/, /2-thiol[³⁵S]/ based on H₂ ³⁵S and C₆H₁₂–/1, 2, 3, 4–¹⁴C_1/4/ has been developed and described.     

Functionalization of 8-aza-D-homogona-1,3,5(10),13-tetraene-12,17a-diones at positions 11 and 17 under the conditions of the claisen ester condensation. Synthesis and properties of 11- and 17-acylsubstituted 8-aza-d-homogonanes

It was shown that 8-aza-D-homogona-1, 3, 5(10),13-tetraene-12,17a-diones enter into the Claisen ester condensation at the C(₍₁₁₎H₂ and C₁₇H₂ groups, whereas the C₍₁₅₎H₂ group is inert under the investigated conditions. It was established that the direction of the reaction is determined by the structure of the 8-azasteroid substrate. In the presence of a bulky gem-dimethyl group at position 16 the reaction takes place exclusively at the C₁₁H₂ group, while in the absence of this restriction the C₍₁₁₎H₂ and C₍₁₇₎H₂ groups are equivalent. The data from IR, UV, and¹H and¹³C NMR spectroscopy of the initial and synthesized derivatives of 3-aza-D-homogonanes are presented and discussed.Institute of Bioorganic Chemistry, Academy of Sciences of Belarus', Minsk. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 959–965, July, 1995. Original article submitted May 6, 1995.     

Circular dichroism of some carotanes

The circular dichroism method has been used to study the stereochemistry of the carotanes. An analysis of the results obtained has shown that an -oriented ester group at C₆ corresponds to a positive Cotton effect (CE) in the 240–260-nm region. A link has been established between the position of the carbonyl group in the ring B and the sign of a CE in the 340-nm region. Hydrolysis of an ester group at C₆ takes place more readily in an alkaline medium than in an acid medium, and in the case of carbonyl-containing carotanes dehydration takes place as well as hydrolysis.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 45–48, January–February, 1984.     

Formation of C1–C5 Hydrocarbons from CCl4 in the Presence of Carbon-Supported Palladium Catalysts

Along with hydrodechlorination, the formation of C₁ and higher hydrocarbons takes place in a flow system in the presence of catalysts containing 0.5–5.0% Pd supported on a Sibunit carbon carrier at 150–230°C. In the entire range of conditions examined, the reaction products are primarily methane, C₂–C₄ hydrocarbon fractions, and C₅ traces. The catalysts are stable in operation, and a high conversion of CCl₄ was retained for a long time interval. The nonselective formation of linear and branched hydrocarbons is indicative of a radical mechanism of the process.     

Study of the fluorite–pyrochlore–fluorite phase transitions in Ln<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> (Ln=Lu,Yb, Tm)

The ordering processes in Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln₂Ti₂O₇ synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln₂Ti₂O₇ takes place at ~740–800 °C. Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm₂Ti₂O₇, Yb₂Ti₂O₇, and Lu₂Ti₂O₇ in air at T>1,600 °C. The conductivity values are 5·10^–3 S/cm for Tm₂Ti₂O₇, 6·10^–3 S/cm for Yb₂Ti₂O₇, and 10^–2 S/cm for Lu₂Ti₂O₇ at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln₂Ti₂O₇ samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003