Migration of the O-acetyl group in the acetonation of guaianolide rhaposerin

Acetonation of rhaposerin is accompanied by migration of the O-acetyl group. Acetonation of 15-O-deacetylrhaposerin afforded isomeric O-isopropylidene derivatives containing five- and six-membered rings.     

Rhaposerine and rhaserolide, new sesquiterpene lactones fromRhaponticum serratuloides

Two new crystalline guaianolides,viz., rhaposerine and rhaserolide, were isolated from an ethanolic extract of the above-ground part of the plantRhaponticum serratuloides by column chromatography along with sesquiterpene lactones,viz., centaurepensin and acroptilin, which have been found in other plants. The chemical structures of the title lactones were established by¹H and¹³C NMR spectroscopy and 2D¹H−¹H (COSY) and¹³C−¹H (COSY and COLOC) NMR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2010–2014, October, 1999.     

Synthesis and crystal structure of a new methooytrichloro derivative of achillin

A new trichlorometoxy derivative of achillin was isolated from the mixture of chlorination products of achillin in MeOH. The structure of this product was established by X-ray diffraction analysis. This confirmed the previously proposed stereochemistry for the molecules of other two products of this reaction.     

Synthesis of two new chloro derivatives of the guaianolide grossmisin and the crystal structure of one derivative

The reaction of grossmisin (8α-hydroxyachillin,1) with chlorine in benzene afforded a mixture of products. The less polar product readily crystallized after chromatography. According to the X-ray diffraction data, this product has the structure of 1α,10β-dichloro-1,10-dihydrogrossmisin. The second chloro derivative of grossmisin,viz., 8β-chloroachillin, was prepared in good yield by the reaction of lactone1 with PCl₅ in CHCl₃ in the presence of Py. Published inIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 11, pp. 1932–1934, November, 2000.     

Ajanolide A, a new germacranolide fromAjania fruticulosa

A new germacranolide, ajanolide A, was isolated from aerial parts ofAjania fruticulosa by means of extraction with CHCl₃ and adsorption chromatography. This compound was identified as (1(10)E,3S,4Z,6R,7S,11R)-3-acetoxygermacra-1(10),4-dien-12,6-olide ((1S,7S,10R,13R)-7-acetoxy-4,8,13-trimethyl-11-oxabicyclo[8.3.0]trideca-4(E),8(Z)-dien-12-one) by X-ray diffraction analysis. 2D¹H−¹H (COSY) and¹³C−¹H (COSY) NMR spectroscopy was used for assigning the¹H and¹³C NMR signals in the spectra of ajanolide A. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 167–170, January, 1998.     

Structure elucidation and complete NMR spectral assignments of two new sesquiterpene lactone xylosides from Lactuca triangulata

Two new sesquiterpene lactone xylosides, derivatives of the guaianolides 9alpha-hydroxyleucodin and 9alpha-hydroxy-11,13-dehydroleucodin, were isolated from roots of Lactuca triangulata. Their structures were established on the basis of (1)H and (13)C NMR spectra, 2D NMR (HMQC, HMBC, COSY, NOESY) techniques and comparison with the literature data. The compounds represent the first example of sesquiterpene lactone xylosides.     

Crystal and molecular structure of subchrysine (3-O-acetylridentine), a new germacranolide fromArtemisia subchrysolepis

A new sesquiterpenoid lactone was isolated from terrestrial parts ofArtemisia subchrysolepis Filat. and studied by X-ray diffraction analysis and CD spectroscopy. This compound was called subchrysine and identified as (1R,3S,4E,6R,7S)-3-acetoxy-1-hydroxygernmacra-4,10(14), 11(13)-trien-12,6-olide. Pronounced temperature dependence of the¹H and¹³C NMR spectra of subchrysine was observed. The results of conformational analysis of subchrysine by quantum-chemical (PM3) and molecular mechanics (MMX) methods are also presented. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1429–1433, July, 1998.     

Study of alkaloids from the flora of the Siberian and Altai regions. 6. Crystal and molecular structure of songorine Z-oxime

Oximation of songorine afforded a mixture of its Z- and E-oximes. The crystal and molecular structure of the Z-isomer was established by X-ray diffraction analysis. Its structure was also confirmed by the spectral data (2D ¹H—¹H and ¹³C—¹H NMR spectroscopy and mass spectrometry). The structure of isomeric E-oxime was established by comparing its NMR spectroscopic data (¹H and ¹³C) with the data for the Z-isomer.     

Isolation and structure determination of pulicazine, a new sesquiterpene lactone from the Tunisian Pulicaria laciniata (Coss.et Kral.) Thell.

A new naturally occurring pseudo-guaianolide type sesquiterpene lactone named pulicazine along with ent-11β,15β-dihydroxykaur-16-en-19-oic acid is isolated from the Tunisian Pulicaria laciniata (Coss.et Kral.) Thell. flowers. Their structures were elucidated by NMR spectroscopy and their stereochemistries were established by X-ray diffraction.     

Total assignment of 1H and 13C NMR data for the sesquiterpene lactone 15-deoxygoyazensolide

We describe a complete analysis of the 1H and 13C spectra of the anti-inflamatory, schistossomicidal and trypanosomicidal sesquiterpene lactone 15-deoxygoyazensolide. This lactone, with a structure similar to other important ones, was studied by NMR techniques such as COSY, HMQC, HMBC, Jres and NOE experiments. The comparison of the data with some computational results led to an unequivocal assignment of all hydrogen and carbon chemical shifts, even eliminating some previous ambiguities. We were able to determine all hydrogen coupling constants (J) and signal multiplicities and to confirm the stereochemistry. A new method for the determination of the relative position of the lactonization and the position of the ester group on a medium-sized ring by NMR was developed.     

Chlorination of tectochrysin and pinostrobin in methanol

The reactions of the natural flavonoids tectochrysin and pinostrobin with chlorine in methanol afforded for the first time their 6,8-dichloro derivatives. Under the reaction conditions, dichloropinostrobin was transformed further into a tetrachloromethoxy derivative. The molecular structure of the latter was established by X-ray diffraction analysis.     

Xyloccensin X and Y, two new limonoids from xylocarpus molluccensis: NMR investigation in mixture

Two new limonoids, xyloccensin X (1) and xyloccensin Y (2), have been identified in mixture using NMR spectroscopy. Both limonoids were isolated in mixture from the fruit of the plant Xylocarpus molluccensis. The structures of these were proposed after extensive 2D NMR analyses in mixture.     

Triterpenoids fromAbies species 19. (22Z)-3α-Hydroxy-17,14-fridolanosta-7,14,22,24-tetraen-26,23-olide,a new lactone from the needles of the Siberian fir

A new triterpenoid lactone with a reported rearranged lanostane skeleton was isolated from the neutral fraction of the extract from the needles of Siberian fir. Its structure was established on the basis of chemical transformations and NMR spectra using two-dimensional (COSY, COLOC) NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp.2792–2794, November,1996For Part 18 see Ref. 1.     

A 2-phenoxychromone from Artemisia rupestris

A 2-phenoxychromone, 6-demethoxy-4′-O-methylcapillarisin, was isolated from Artemisia rupestris L. The structure of this compound was established by analysis of the spectroscopic data. A single-crystal diffraction analysis was performed in order to confirm the proposed structure. Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 14–15, January–February, 2006.     

Two new coumarin biosides from Angelica dahurica

Two new coumarin biosides, tert-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranosyl-byakangelicin (1) and 2′-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranosyl-peucedanol (2), were isolated from the fresh roots of Angelica dahurica. The structures of the new compounds were elucidated on the basis of spectral analysis. Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2008.     

Selectivity of methylation of some new [1,2,3]triazolo[4,5-d]pyridazines and structure elucidation by H–N NMR spectroscopy

Alkylation of some selected [1,2,3]triazolo[4,5-d]pyridazines having five or more nitrogen atoms capable for alkylation was investigated. Pyridyl derivatives substituted also on the [1,2,3]triazole ring gave quaternary pyridinium salts, whereas in the case of the analogues compounds unsubstituted at the triazole moiety, the alkylation of the triazole ring was also observed. Unambiguous structure elucidation was provided by ¹H–¹⁵N HMBC experiments which also allowed the assignment of the ¹⁵N NMR shifts.     

Physicochemical properties of new cellulosic fibers from the bark of Acacia arabica

With the growing environmental consciousness toward carbon emissions, natural fibers are the best alternative and act as a substitute for synthetic fibers due to their potential properties. New cellulosic fibers were identified from Acacia arabica bark. This study aimed at understanding the characteristics of Acacia arabica fibers (AAFs) extracted from the bark of the A. arabica, and its physicochemical properties were examined by thermal stability analyses, X-ray diffraction, chemical constitutions, and Fourier transform infrared spectroscopy analysis. Cellulose content (68.1 wt%), density (1028 kg m^?3), and crystallinity index (51.72%) properties were identified.     

Synthesis, spectrophotometry, and X-ray diffraction studies of a new salt: p-xylylenebis(tetrahydrothiophenium) bis(triiodide)

A new salt, p-xylylenebis(tetrahydrothiophenium) bis(triiodide) C₁₆H₂₄I₆S₂, was prepared. The molecular structure of the salt was studied by X-ray diffraction; the factors that form the crystal packing represented by...Ct...I₃...I₃...Ct... type chains (Ct is cation) were identified. The stability of p-xylylenebis(tetrahydrothiophenium) diiodochlorides and triiodides was estimated by spectrophotometry using the average iodine number function . Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1341–1344, July, 2007.     

Ti-Co-SBA-15的制备、表征及其选择氧化催化性能

以钛酸丁酯为钛源,分子筛SBA-15为载体,采用水热法合成了一系列不同载钛量的Ti-SBA-15分子筛,用浸渍法将钴负载于其骨架结构上,得到Ti-Co-SBA-15催化剂。采用X射线、N₂吸附-脱附、漫反射紫外-可见光谱和傅里叶变换红外光谱等方法对样品进行了表征,并考察了催化剂在温和条件下对叔丁基甲苯氧气氧化反应中的催化性能。结果表明,所制备的催化剂样品具有较大的比表面积和孔径,钛、钴以四配位体存在,具有较高的催化活性和选择性,可获得较高的对叔丁基苯甲醛收率。