Cerium(IV) based oxidative free radical cyclization of active methylene compounds with some cyclic alkenes: A useful annulation method for terpene functionalization

Ceric ammonium nitrate-mediated oxidative cyclizations of CH-acids with terpenes and terpene like substrates were investigated. Dimedone, acetylacetone, and methyl nitroacetate were condensed with pinene, norbornene, nopol, camphene, and carvone and the reaction stereoselectivity was examined. Condensation with endocyclic double bonds in pinene and nopol displayed stereoselectivity, resulting in the formation of pure enantiomers. Condensation with exocyclic double bonds in camphene and carvone produced enantiomer mixtures. The mechanism of the intramolecular annulation in a nopol derivative is discussed with the help of DFT and ab initio calculations.     

Separation of attogram terpenes by the capillary zone electrophoresis with fluorometric detection

An original method based on capillary zone electrophoresis with fluorimetric detection has been developed for the determination of terpenic compounds. The method is based on the separation of a terpenes dynamically labeled by the non-ionogenic tenside poly(ethylene glycol) pyrenebutanoate, which was used previously for the labeling of biopolymers. The background electrolytes were composed of taurine-Tris buffer (pH 8.4). In addition to the non-ionogenic tenside aceton and poly(ethylene glycol) were used as the additives. The capillary zone electrophoresis with fluorometric detection at the excitation wavelength 335 nm and the emission wavelength 463 nm was successfully applied to the analysis of tonalid, cholesterol, vitamin A, ergosterol, estrone and farnesol at level of 10(-17) mol L(-1). Farnesol, is produced by Candida albicans as an extracellular quorum-sensing molecule that influences expression of a number of virulence factors, especially morphogenesis and biofilm formation. It enables this yeast to cause serious nosocomial infections. The sensitivity of this method was demonstrated on the separation of farnesol directly from the cultivation medium.     

Chemomicrobial synthesis of (R)- and (S)-lavandulol

(R)- and (S)-Lavandulol are important compounds in the cosmetics industry and in pheromone research. We have developed syntheses of (R)- and (S)-lavandulol from (S)- and (R)-limonene, respectively, by microbial Baeyer-Villiger oxidation of the intermediate unsaturated hydroxy ketone. It has been found that the same strain of Acremonium roseum can be successfully used in the key step of the synthesis of both enantiomers of lavandulol.     

Synthesis and olfactory properties of unnatural derivatives of lilac aldehydes

Lilac aldehydes are considered as principal olfactory molecules of lilac flowers. We have designed, prepared and evaluated two sets of their unnatural racemic analogues as pure diastereomers. While the synthesis of gem-dimethyl homologues starts from geranyl acetate, the preparation of methylene derivatives commences from linalyl acetate. The key Lewis and/or Brønsted acid catalysed cyclisation furnishes easily separable cis-/trans-tetrahydrofuranyl esters as common advanced intermediates. The subsequent functional group transformations lead to target aldehydes, alcohols, nitriles and olefins. Unlike the homologues possessing similar herbal scents, methylene derivatives exhibit woody and/or flowery odours. In the latter case, the sensory evaluation suggests the importance of relative stereochemistry and/or type of functional group on the odour character of respective compounds.     

Arjunolic Acid in Molecular Recognition: First Synthesis and Cation Binding Studies of a novel Arjuna-18-crown-6

Arjunolic acid, a functionally rich chiral triterpenoid with a rigid pentacyclic backbone, has the potential to be used as a structural framework for the design of molecular receptors and supramolecular architectures. The design and synthesis of the first arjunolic acid-derived 18-crown-6 and its binding studies with metal and tert-butylammonium ions are reported.     

基于天然萜类的可持续性聚合物

随着可持续发展观念的逐步深入,可持续性聚合物已发展成为当今高分子领域的研究热点之一.萜类化合物作为自然界中一类来源广泛的天然资源,具有多种可修饰位点和丰富的功能性,由它出发制备可持续性聚合物,不仅可以简化聚合物的合成步骤,还可以赋予聚合物独特的立体构型、良好的生物活性和生物相容性等特点,进而拓展其在表面涂层、生物医药、组织工程等领域中的应用.本文综述了近年来国内外基于天然萜类可持续性聚合物的研究进展,从萜类化合物的结构特点出发,系统介绍了基于天然萜类可持续性聚合物的合成策略、特性及应用.     

A novel and efficient catalytic epoxidation of olefins and monoterpenes with microencapsulated Lewis base adducts of methyltrioxorhenium

The reactivity of methyltrioxorhenium in the epoxidation of olefins can be tuned by the presence of Lewis bases as ligands of the metal center. Unfortunately, a large excess of ligand is usually required to obtain high yields and selectivities mainly because of the fluxional behaviour that these compounds show in solution. We describe here the microencapsulation technique that can resolve this problem. Microencapsulated Lewis base adducts of methyltrioxorhenium with nitrogen containing ligands are highly efficient and selective catalysts for the epoxidation of several olefins and monoterpenes with hydrogen peroxide even in the case of the most sensitive substrates. These systems show the advantages of the ligand accelerated catalysis and the benefits of heterogeneous compounds. They can be easily recovered from the reaction mixture and used for more transformations.     

Degradation of the Side Chain of (−)‐Sclareol: A Very Short Synthesis of nor‐Ambreinolide and Ambrox

Abstract

The synthesis of nor‐Ambreinolide (8) from (‐)‐sclareol (1) was carried out by treatment with KMnO₄‐Ac₂O and further alkaline hydrolysis. 8 was directly transformed into (‐)‐ambrox (11) by reduction with metal borohydride in the presence of Lewis acids.     

A new approach to A/B ring analogue of eleutherobin and sarcodictyns through a sequence of highly diastereofaceselective Diels-Alder reaction and ring opening-ring closing metathesis (RO-RCM)

An approach to the construction of A/B ring analogue of antitumour compounds eleutherobin and sarcodictyns is described. The key steps involve a highly diastereofaceselective Diels-Alder reaction of a dienophile containing a furanosugar moiety with cyclopentadiene and ring opening-ring closing metathesis of the resulting adduct.     

A simple strategy for the synthesis of optically pure trans-hydrindane systems

A new strategy for the synthesis of optically pure trans-hydrindane systems is reported from an easily available starting material.