Chemistry and Structure of Diterpene Derivatives of the Kaurane Series: V. Isosteviol Anhydrides

(4,8,13)-13-Methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) anhydride is synthesized, which is a first representative of bisditerpene compounds of the kaurane series. The structures of the anhydride and isosteviol chloride were studies by X-ray diffraction and quantum chemistry (AM1).     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: VI. Isosteviol Esters

Esterification with alcohols and diols of (4,8,13)-13-methyl-16-oxo-17-norkaurane-18-carboxylic acid chloride prepared by treatment of the acid (isosteviol) with thionyl chloride yields the corresponding esters. The molecular and crystal structures of a series of esters were determined by single crystal X-ray diffraction. The diethylene glycol diester in the crystal has a tweezer structure with an intramolecular cavity. The supramolecular structure of some isosteviol derivatives in the crystal is characterized by alternation of lipophilic and hydrophilic regions.     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: VIII. Azomethines Derived from Isosteviol

(4,8,13)-13-Methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) and its methyl ester were reacted with benzylamine and hydroxylamine to obtain the corresponding E-stereoisomeric 16-ketimines. Isosteviol benzylimine and oxime form individual 1:1 H-bonded complexes with methanol and water, respectively.     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: IX. Electrochemical Reactions of Isosteviol and Its Derivatives

The keto group in (4,8,13)-13-methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) is not polarographically reduced in DMF. Isosteviol methyl ester and oximes, too, are not reduced under these conditions. Isosteviol oxime is oxidized electrochemically or with lead dioxide, yielding iminoxyl radical.     

The Crystal Structure of Isosteviol

The title compound was prepared and its crystal structure was determined using X-ray crystallographic method. The crystal is orthorhombic, space group is P212121 with a= 1. 1114(2) nm, b=1.7677(3) nm, c=1.8312(3) nm; Z=8. The geometric structure and conformation of the title compound obtained by MMX molecular mechanics calculation are in agreement with those obtained from X-ray determination.     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: VII. Chiral Complexes of Isosteviol with Aromatic Compounds

(4,8,13)-13-Methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) forms with aniline, dimethylaniline, and toluene individual 2:1 molecular complexes whose crystals are isostructural. According to X-ray diffraction data, the supramolecular crystal structure of these complexes is formed by chiral double helices with a 4₃ screw axis, consisting of isosteviol molecules. The strands of the helices are linked together by intermolecular hydrogen bonds involving the carboxy and carbonyl groups of two isosteviol molecules of neighboring helices. In their turn, the two hydrogen-bonded isosteviol molecules form head-to-tail pseudocage dimers. The aromatic guests occupy fairly large cavities between the strands of isosteviol helices.     

Synthesis and Crystal Structure of Isosteviol Derivatives

Isosteviol (ent-16-ketobeyeran-19-oic acid, I) is a tetracyclic diterpenoid with a beyerane skeleton obtained by acid hydrolysis of stevioside.1 Several tetracyclic diterpenoids, specially the kaurenes, have important biological activities. Recent studies on the microbial transformation of isosteviol have revealed that it is metabolized by Cunninghamella bainieri, Actinoplanes sp., Mucor recurvatus, and Cunninghamella blackesleeana to yield five new metabolites.2 The hydroxylation pattern of these bioactive compounds may influence their binding on to the receptors, as was proposed for the Rabdosia diterpenoids. Therefore, the introduction of hydroxyl groups or unsaturated bonds in saturated and non-hydroxylated diterpenoids, like isosteviol, may enhance existing properties or lead to new biological activities. Although some beyeranes have been subjected to biotransformations by fungi,4 there are few report in the literature related the chemical transformation of Isosteviol. In the present study, we try to develop the chemical transformation of isosteviol and other beyeranes in order to obtaining some bioactive compounds with beyerane skeleton. Seven isosteviol derivatives, Ⅱ-Ⅷ, were therefore synthesized and characterized. The X-ray crystal strcture of H(R = H) was also determined.     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: IV.1 Acylation of Reduction Products of the Isosteviol Keto Group

Acetylation with acetic anhydride of (4,8,13)-16-hydroxy-13-methyl-17-norkaurane-18-carboxylic acid and its methyl ester, obtained by reduction of isosteviol and (4,8,13)-18-methoxycarbonyl-13-methyl-16-oxo-17-norkaurane, respectively, gives rise to (4,8,13)-16-acetoxy-13-methyl-17-norkaurane-18-carboxylic acid and (4,8,13)-16-acetoxy-18-methoxycarbonyl-13-methyl-17-norkaurane. The molecular and crystal structures of the compounds were established by X-ray diffraction.     

Diterpenoids ofPulicaria salviifolia. II. Structure of salvicin

A new diterpenoid acid of the clerodane series, C₂₀H₃₂O₄, [] _D ²⁰ –75.4° (c 0.26; methanol), which has been called salvicin, and the known flavonoid rutin have been isolated from a chloroform extract of the epigeal part ofPulicaria salviifolia. The structure of salvicin has been established on the basis of spectral characteristics and chemical transformations.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 299–301, May–June, 1986.     

中国大戟属植物中二萜成分的化学及生物活性

大约有80种大戟属植物广泛分布于我国,并在民间用来治疗皮肤病、水肿、结核或作为泻药和利尿剂使用.本文综述了近20年来中国产大戟属植物中14个骨架类型共150多个二萜类成分的化学研究,包括最近报道的4个具有新骨架的二萜和2个二聚体.中国产大戟属植物中的一些二萜类成分具有抗肿瘤、抗病毒、促进神经生长因子增长、皮肤刺激、致癌以及镇痛安神的活性.本文还就大戟属中二萜类成分可能的生源代谢途径提出了假设,并对该属未来的研究进行了展望.     

Cationic Bismuth Amides: Accessibility,Structure, and Reactivity

The synthetic access to cationic bismuth compounds based on simple, monodentate, synthetically useful amido ligands, [Bi(NR₂)₂(L)_n]⁺, has been investigated (R=Me, iPr, Ph; L=neutral ligand). With [BPh₄]^? as a counteranion, the formation of contact ion pairs and subsequent phenyl transfer from B to Bi is observed. An intermediate of this reaction, [Bi(NMe₂)₂(HNMe₂)(BPh₄)] ( 1 ), could be isolated and fully characterized. The use of a fluorinated tetraarylborate as a counteranion leads to more stable cationic bismuth amides. The solvent‐separated ion pairs [Bi₂(μ₂‐NMe₂)₂(NMe₂)₂(thf)₆]²⁺ ( 4 ) and [Bi(NiPr₂)₂(thf)₃]⁺ ( 5 ) were fully characterized, with [B(3,5‐C₆H₃(CF₃)₂)₄]^? anions balancing the positive charge. The coordination chemistry, aggregation in solution, and spectroscopic features of these compounds were investigated. Compounds 4 and 5 show an increased reactivity towards diisopropylcarbodiimide compared to their neutral parent compounds. These reactions result in formation of the first cationic bismuth guanidinates. Characterization techniques include ¹H, ¹¹B, ¹³C, ¹⁵N, ¹⁹F, and ³¹P (VT)NMR and IR spectroscopy, single crystal X‐ray diffraction analysis, and DFT calculations.     

Isolation and Structure Determination of New Jatrophane Diterpenoids from Euphorbia platyphyllos L.

Three new, highly functionalized jatrophane diterpenes ( 1 – 3 ) have been isolated from the whole, dried plants of Euphorbia platyphyllos L., together with one known jatrophane polyester ( 4 ). The structures were established by UV/VIS spectroscopy, HR‐ESI‐MS, and advanced two‐dimensional NMR, including ¹H‐NMR, JMOD, ¹H,¹H‐COSY, HMQC, and HMBC experiments. Stereochemical studies and conformational analyses were performed by means of NOESY experiments. Interestingly, compounds 1 – 4 do not represent a stereochemically uniform series because they differ in the orientations of the Me groups at C(2), C(6), and C(13). A similar observation was reported earlier for Euphorbia serrulata, whose diterpenes are related to the compounds obtained from E. platyphyllos. This chemical relationship is of taxonomic importance and supports the botanical similarity of the two species.     

Trifluoroethylene Sultone: Structure and Chemistry

The gas phase structure of trifluoroethylene sultone, ( 1 ) (3,4,4-trifluoro-1,2-oxathietane-2,2-dioxide) was determined by gas electron diffraction, and the four-membered ring was found to be planar. The following ring parameters (r_a distances and ∠_α angles with 3σ uncertainties) were derived in the electron diffraction analysis: C? O = 1.41 Å (ass.), C? C = 1.541(18) Å, S? O = 1.652(5) Å, S? C = 1.822(8) Å, S? C? C = 86.2(15)°, C? C? O = 97.1(28)°, C? O? S = 97.5(21)°, and O? S? C = 79.1(8)°. New spectral data (IR, NMR) of 1 , its acyclic isomer FSO₂CFHC(O)F ( 2 ), and the related anhydride, FSO₂OSO₂CFHC(O)F ( 3 ), are reported. New esters containing the fluorosulfonyl function, FSO₂CFHC(O)OCH₂CF₃ ( 4 ), FSO₂CFHC(O)OCH₂CH = CH₂ ( 5 ), and (FSO₂CFHC(O)OCH₂CH? CH₂? )_n ( 6 ) have been prepared and characterized.     

New Tricyclic Amides. Synthesis,Structure, and Oxidation with Peroxyphthalic Acid

4-Azatricyclo[5.2.1.0^2,6]dec-8-ene was synthesized and brought into reactions with benzoyl, o-chlorobenzoyl, p-bromobenzoyl, p-, m-, and o-nitrobenzoyl, and bicyclo[2.2.1]hept-2-ene-endo-5,endo-6-dicarboximidoacetyl chlorides in chloroform in the presence of pyridine. The tricyclic amides thus obtained were epoxidated with peroxyphthalic acid prepared in situ by reaction of phthalic anhydride with a 35% aqueous solution of hydrogen peroxide. The structure of newly synthesized compounds was confirmed by IR and ¹H and ¹³C NMR spectroscopy and mass spectrometry. Their NMR spectra were compared with those of previously synthesized N-arylsulfonyl-4-azatricyclo[5.2.1.0^2,6]dec-8-enes on the basis of conformational composition of the corresponding p-nitrophenyl-substituted derivatives, which was determined by PM3 semi-empirical quantum-chemical calculations.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 837–845.Original Russian Text Copyright © 2005 by L. Kas’yan, Okovityi, Tarabara, A. Kas’yan, Bondarenko.     

The Structure of Silylated Amides: N-Methyl-N-Trimethylsilyltrifluoroacetamide,a Reassignment of structure

The ²⁹Si and ¹⁴N nmr spectra of some bissilylamides and monosilylamides are reported. The results are compared with those for model silylesters, amines and imines. The compound of formula CF₃CONCH₃Si(CH₃)₃ (MSTFA) is shown to exist as a tautemeric mixture of a silylamide and a silylimidate. This assignment is confirmed by ¹³C nmr. A rationale is proposed for the structure directing effect of substituents on the amide carbon atom.     

Structure Elucidation of Two New Diterpenoids from Isodon phyllostachys: Phyllostacins A and B

Two new ent‐kaurane‐derived diterpene derivatives, phyllostacins A ( 1 ) and B ( 2 ), were isolated from the aerial parts of Isodon phyllostachys, together with two known compounds, irroratin A ( 3 ) and serrin B ( 4 ). Both 1 and 2 were found to be present as diastereoisomers. In the case of 1 , the corresponding diastereoisomeric diacetates 5 and 6 were prepared and separated. The structures of the new compounds were elucidated by extensive 1D‐ and 2D‐NMR spectroscopic methods, in combination with MS experiments. In (D₅)pyridine solution, the two epimers of 1 are present in equal amounts, but in CDCl₃ or CD₃OD, the (S)‐epimer predominates in the mixture of hemiacetals.     

第26届国际化学奥林匹克竞赛理论试题

在剧烈运动时在肌肉里产生乳酸(缺氧代谢)。在血液中,乳酸和碳酸氢盐发生中和反应。可通过如下计算来说明此过程:乳酸是一元酸,用HL表示。它的电离常为:KHL=1。4*-14