Stereochemical features of the structure of germacrane lactones and the applicability of Geissman's rule in this series

Stereochemical features of the structure of the germacrane lactones have been investigated. By correlating the circular dichroism and the results of x-ray structural analyses of the germacranolides with different types of linkage of the lactone ring it has been estabished that Geissman's rule is satisfied in the trans-trans-germacral(10), 4-dienolide series if the lactone ring has the S-conformation and the decadiene ring the chair-chair conformation in the C₆-trans-lactones and, correspondingly, the A and chair-chair conformations in the C₆-cis compounds. The decadiene ring has the boat-boat conformation if there is an exocyclic double bond at C₁₀ in the C₈-trans-germacrolides, and a positive Cotton effect (CE) is observed in the CD spectra in the 220 nm region and a negative one at 200 nm.Institute of Chemistry of Plant Substances Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 742–748, November–December, 1990.     

Spatial structure of the germacrane lactones hanphyllin,salonitenolide, and sachosin

An x-ray structural study has been made of the sesquiterpene lactones hanphyllin, salonitenolide, and sachosin: diffractometer; CuK_α radiation; 997, 950, and 1245 reflections, respectively; direct method; R factors 0.049, 0.099, and 0.081. All three molecules have the chair-chair conformation with configurations of the₁D¹⁴ and¹⁵D₅ types. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 775–780, November–December, 1989.     

Spatial structure of the germacrane lactones hanphyllin, salonitenolide, and sachosin

An x-ray structural study has been made of the sesquiterpene lactones hanphyllin, salonitenolide, and sachosin: diffractometer; CuK radiation; 997, 950, and 1245 reflections, respectively; direct method; R factors 0.049, 0.099, and 0.081. All three molecules have the chair-chair conformation with configurations of the₁D¹⁴ and¹⁵D₅ types.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 775–780, November–December, 1989.     

Spatial structures of the sesquiterpene germacrane lactones tanachin and tamirin

An x-ray investigation has been made of the sesquiterpene lactones tanachin and tamarin: diffractometer, CuK-radiation, 845 and 981 reflections, respectively, direct method, R factors 0.064 and 0.065. The conformations of both molecules are boat-boat with configurations of the¹D₁₄ and¹⁵D₅ types.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Institute of Bioorganic Chemistry, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodynkh Soedinenii, No. 2, pp. 198–204, March–April, 1989.     

Circular dichroism of some sesquiterpene lactones of the germacrane type

The CD spectra of a series of germacranolides have been considered, and the parameters of the Cotton effects observed have been correlated with the stereochemistries of the compounds studied. The applicability for germanocranolides of the Waddell-Stocklin-Geissman rule is discussed.Deceased.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 176–179, March–April, 1986.     

Stereochemical features of the synthesis and the structure of fullerenes

Details of the design of decaplet fullerenes are discussed. A model of the cluster assembly of C₆₀, C₇₀, and C₈₀ monomers from mono-, bi-, and trihexacyclic compounds of carbon was developed on the basis of the described structural and stereochemical concepts. The autoadhesion in the supermolecular structure, the cluster macrorecombination of the π radicals, and the contribution from spin-polymerization effects to regulation of the organic synthesis of C_n fullerenes were examined. V. N. Bakul Institute of Superhard Materials, National Academy of Sciences of Ukraine, 2 Avtozavodskaya ul., Kiev 254074, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 145–149, May–June, 1999.     

Spatial structure of the dimeric sesquiterpene germacrane lactone mikagoyanolide

The dimeric sesquiterpene lactone mikagoyanolide (I) has been isolated from the plantTanacetopsis mucronata. The spatial structure of (I) has been determined by the x-ray structural method (R=0.086, 1161 reflections). The dimeric lactone is formed from cyclodecadienes of the germacrolide and melampolide types having chair-chair and boat-chair conformations. The conformational state of the free molecule of (I) has been calculated by the method of molecular mechanics.Institute of Chemistry of Plant Substances, Uzbekistan Republic of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 213–217, March–April, 1993.     

Conformational analysis of sesquiterpene lactones of the germacrane type 1. 1(10)E,4E-Germacranolides

The structure of 1(10)E,4E-germacranolides was studied by a molecular mechanics method. Possible conformers, the probabilities of their occurrence, and the barriers to conformational transitions were determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp, 2890–2893, December, 1996.     

Stereochemical structure of β-methoxyethylbenzenes

Conclusions For solutions of -methoxyethylbenzenes in nonpolar solvents it was established that the conformation with the gauche-orientated substituents in relation to the bond is preferred and the conformation with close Me and Ph groups is realized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1033–1037, May, 1987.     

Stereochemical features of bromine- and iodine-containing compounds of lanthanides

The Voronoi-Dirichlet (VD) polyhedra and the intersecting spheres method have been used to analyze the features of the environment of lanthanide (Ln) atoms consisting of bromine and iodine atoms in the structures of 94 compounds containing 96 LnBr _n complexes and 41 LnI _n complexes. The lanthanum CN with respect to halogen atoms varies from 6 to 9. The volume of the VD polyhedra of Ln atoms depends only on the oxidation state of the metal atom and the nature of the surrounding atoms.     

Specific features of tetrahydrofuran copolymerization with lactones

Mechanistic features of the cationic copolymerization of lactones with cyclic ethers are studied for β-propiolactone (PL) with tetrahydrofuran (THF) and ?-caprolactone (CL) with THF. It is shown that, in the PL-THF system at [THF]₀ > [THF]_e, the copolymer is considerably enriched with the more basic THF whereas at [THF]₀ < [THF]_e anomalous enrichment of the copolymer with the less basic PL is observed. The mechanism of this phenomenon, which is applicable to many other cases and causes the formation of block copolymers from some heterocyclic monomers, is considered. At concentrations below equilibrium, THF is incorporated in the copolymer as pairs of units due to the effect of the penultimate unit on the thermodynamics of its addition.     

Molecular and crystal structure of jurineolide — A germacrane lactone from Jurinea multiflora

By extraction with chloroform, followed by treatment of the total extractive substances with hexane and chromatography of the resulting precipitate, the epigeal part ofJurinea multiflora has yielded a sesquiterpene lactone of the germacrolide type, jurineolide. The following spatial structure is proposed for jurineolide: 8α-(4′-hydroxytigloyloxy)-6β,7α(H)-germacra-trans-1(10),trans-4(5),11(13)-trien-6,12-olide. Institute of Organic Synthesis and Coal Chemistry, Central Kazakhstan Branch, Academy of Sciences of the Kazakh SSR. Translated from Khimiya Prirodnykh Soedinii, No. 4, pp. 490–494, July–August, 1991.     

Stereochemical features of diterpene alkaloids in acylation and alkaline hydrolysis reactions

Summary Relative difficulty of saponifying an acetoxy group at C₁ and ease of acylation of a hydroxy group in this position as compared with a hydroxy group C₁₀ has been shown for alkaloids with a lycoctonine skeleton.The anomalously easy saponification of a C₁-acetoxy group in karakolidine acetates is due to the influence of the neighboring C₁₃-hydroxy group.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 381–383, May–June, 1975.     

New approach to the synthesis of lactones of the iridane series

A new approach to the synthesis of lactones of the iridane series starting from (±)-linalool was developed. Synthesis of a bicyclic iridoid structurally related to the naturally occurring iridolactone villosol was performed.     

Vapor-phase hydrogenation in the GLC analysis of sesquiterpene lactones of the eudesmane series

The GLC analysis has been carried out of the products of the vapor-phase hydrogenation of the unsaturated lactoens ofInula helenium L. Tetrahydroalantolactone has been detected for the first time in elecampane rhizones and roots. During the vapor-phase hydrogenation of the compounds being analyzed in the presence of a Ni catalyst, a migration of the exocyclic double bond of isoalantolactone and of dihydroisoalantolactone was observed.All-Union Scientific-Research Institute of Drug Chemistry and Technology, Kharkov. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 797–801, November–December, 1991.     

Vapor-phase hydrogenation in the GLC analysis of sesquiterpene lactones of the eudesmane series

The GLC analysis has been carried out of the products of the vapor-phase hydrogenation of the unsaturated lactoens ofInula helenium L. Tetrahydroalantolactone has been detected for the first time in elecampane rhizones and roots. During the vapor-phase hydrogenation of the compounds being analyzed in the presence of a Ni catalyst, a migration of the exocyclic double bond of isoalantolactone and of dihydroisoalantolactone was observed. All-Union Scientific-Research Institute of Drug Chemistry and Technology, Kharkov. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 797–801, November–December, 1991.