An improved synthesis of 5-thio-D-ribose from D-ribono-1,4-lactone

5-Thio-D-ribopyranose was synthesized from D-ribono-1,4-lactone (1) by two approaches: (i) 5-bromo-5-deoxy-D-ribono-1,4-lactone (2) was successively transformed into 5-bromo-5-deoxy, 5-S-acetyl-5-thio or 5-thiocyanato-D-ribofuranose derivatives; appropriate treatment then lead to 5-thio-D-ribopyranose (7) in 46-48% overall yield and; (ii) 2 was transformed into the 5-S-acetyl-5-thio-D-ribono-1,4-lactone derivative (11). Reduction and deprotection of 11 afforded 5-thio-D-ribopyranose (7) in 57% overall yield.     

Tetra-n-propylammonium tetra-oxoruthenate(VII): a reagent of choice for the oxidation of diversely protected glycopyranoses and glycofuranoses to lactones

2,3,4,6-Tetra-O-benzyl- -glucopyranose, 2,3,5-tri-O-allyl- -ribofuranose, 2,3,5-tri-O-allyl- and -tri-O-benzyl- -arabinofuranose, and 2-deoxy-3,5-di-O-allyl- -erythro-pentofuranose were oxidized to their corresponding lactones 6–10 by dimethyl sulfoxide activated by oxalyl chloride, pyridinium dichromate in the presence of molecular sieves and acetic acid, and tetra-n-propylammonium tetra-oxoruthenate(VII) using 4-methylmorpholine N-oxide as cooxidant. With the latter reagent, analytically pure lactones were obtained in 83–98% yield. A multistep preparation of 3,4,6-tri-O-benzyl-2-deoxy- -arabino-hexono-1,5-lactone (14) from 3,4,6-tri-O-benzyl-1,5-anhydro-2-deoxy- -arabino-hex-1 enitol (65% overall yield) is described.     

14-Methylpentadecano-15-lactone (muscolide): a new macrocyclic lactone from the oil of Angelica archangelica L

The chemical composition of seed and root oils from Angelica archangelica L. was investigated. Analyses were performed by GC/MS and GC using two columns of different polarities (polyethylene glycol (DB-Wax) and 5% phenyl/95% polydimethylsiloxane (HP-5)), for the separation of several co-eluting components. A total of 58 compounds were identified, accounting for 96.3% (seed) and 93.5% (root) of the oils, respectively. A high content of beta-phellandrene (74.7%) was found in Angelica seed oil. Root oil contained a larger amount of macrocyclic lactones (1.3%) in comparison to the seed oil (0.4%). Different harvest dates produced only slight changes in the root-oil composition. In root oil harvested in summer, the beta-phellandrene content increased by ca. 36%, but no significant changes in the relative compositions of other components were observed. Fresh root oils were collected in five fractions (constant time intervals) during steam distillation (see Table). The highest-boiling fraction contained 9.3% of macrocyclic lactones such as tridecano-13-lactone (5.0%), 12-methyltridecano-13-lactone (0.4%), tetradecano-14-lactone (0.1%), pentadecano-15-lactone (3.5%), 14-methylpentadecano-15-lactone (1; trace), hexadecano-16-lactone (trace), and heptadecano-17-lactone (0.2%). This is the first report of the occurrence of 14-methylpentadecano-15-lactone (muscolide; 1) in a natural product.     

High-performance liquid chromatography-thermospray mass spectrometry of 5,6-dihydroxyeicosatrienoate-1,5-lactone from tissue homogenates

We have developed a method for the analysis of 5,6-dihydroxyeicosatrienoate-1,5-lactone (5,6-DiHETriE-δ-lactone) in tissue homogenates, supplemented with NADPH and arachidonic acid [20:4(n−6)] as a substrate. During the incubation and the extraction, most of the 5,6-epoxyeicosatrienoic acid (5,6-EpETriE) was converted to 5,6-dihydroxyeicosatrienoic acid (5,6-DiHETriE), and most of the 5,6-DiHETriE was converted to 5,6-DiHETriE-δ-lactone. Consequently, the chief degradation product of 5,6-EpETriE and 5,6-DiHETriE in the incubation mixture was 5,6-DiHETriE-δ-lactone. 5,6-DiHETriE-δ-lactone, corresponding to [20:4(n−6)], was shown to be characterized by a high intensity of quasimolecular ions (MH⁺ and MNH₄⁺), using ion analysis obtained by reversed-phase HPLC-thermospray MS. On selected-ion monitoring (SIM) chromatograms of 5,6-DiHETriE-δ-lactone and with deuterium-labeled 15(s)-hydroxyeicosatetraenoic acid as the internal standard, the regression equation of the peak-area ratio and the amount of 5,6-DiHETriE-δ-lactone was y = 12.2x + 0.7 (r = 0.9996). 5,6-Epoxygenase activity was represented as the sum of the amount of 5,6-DiHETriE-δ-lactone, 5,6-EpETriE and 5,6-DiHETriE per mg protein, after 30 min in an incubation mixture. The activity from rat brain homogenate decreased considerably with growth of the rat.     

Confirmation of the structure of tetra-O-(tert-butyldimethylsilyl)-D-glucono-1,4-lactone formed by silylation of D-glucono-1,5-lactone

The structure of tetra-O-(tert-butyldimethylsilyl)-D-glucono-1,4-lactone made by the silylation of D-glucono-1,5-lactone has been confirmed by single-crystal X-ray analysis.     

The Absolute Configuration of Belactin A,a β-Lactone-Containing Serine Carboxypeptidase Inhibitor: Importance of the β-Lactone Structure for Serine Carboxypeptidase Inhibition

Abstract

The absolute configuration of belactin A, a β-lactone-containing serine carboxypeptidase inhibitor was studied by a crystal X-ray diffraction analysis and its absolute structure was determined to be (2R,3S)-2-{(3S)-3-[(2-amino-5-chlorophenyl)carboxamido]-1, 1-dimethy1-2-oxobutyl}-3-methyl-4-oxooxetane. The importance of the β-lactone structure for inhibitory activity was found by preparing several derivatives of belactin A.     

Sesquiterpene and diterpene lactones from Melampodium leucanthum and the molecular structure of 4(5)-dihydromelampodin B

The aerial parts of Melampodium leucanthum afforded a novel diterpene-γ-lactone, 1,6,7-trihydroxy-17-acetoxymelcantholide, and two new sesquiterpene dilactones, 4(5)-dihydrocinerenin and 4(5)-dihydromelampodin C. The known melampolides, leucanthin A, melampodin A acetate, melampolidin and leucanthinin were also isolated. The structure determinations involved spectral and chemical methods. The molecular structure of 4(5)-dihydromelampodin B, determined by X-ray diffraction, is described.     

The roles of redox processes in pea nodule development and senescence

Nodule senescence is triggered by developmental and environmental cues. It is orchestrated through complex but poorly characterized genetic controls that involve changes in the endogenous levels of reactive oxygen species (ROS) and antioxidants. To elucidate the importance of such redox control mechanisms in pea root nodule senescence, redox metabolites were analysed throughout nodule development in a commercial pea variety ( Pisum sativum cv. Phoenix) inoculated with a commercial rhizobial strain ( Rhizobium leguminosarum bv. viciae ). Although a strong positive correlation between nitrogenase activity and nodule ascorbate and glutathione contents was observed, the progressive loss of these metabolites during nodule senescence was not accompanied by an increase in nodule superoxide or hydrogen peroxide. These oxidants were only detected in nodule meristem and cortex tissues, and the abundance of superoxide or hydrogen peroxide strongly declined with age. No evidence could be found of programmed cell death in nodule senescence and the protein carbonyl groups were more or less constant throughout nodule development. Pea nodules appear to have little capacity to synthesize ascorbate de novo . l -galactono-1, 4-lactone dehydrogenase (GalLDH), which catalyses the last step of ascorbate synthesis could not be detected in nodules. Moreover, when infiltrated with the substrates l -galactono-1, 4-lactone or l -gulonolactone, ascorbate did not accumulate. These data suggest that ROS, ascorbate and glutathione, which fulfil well recognized, signalling functions in plants, decline in a regulated manner during nodule development. This does not necessarily cause oxidative stress but rather indicates a development-related shift in redox-linked metabolite cross-talk that underpins the development and aging processes.     

Synthesis and Topoisomerase I inhibitory properties of klavuzon derivatives

Klavuzon is a naphthalen-1-yl substituted α,β-unsaturated δ-lactone derivative, and is one of the anti-proliferative members of this class of compounds. Asymmetric and racemic syntheses of novel α,β-unsaturated δ-lactone derivatives are important to investigate their potential for the treatment of cancer. In this study, asymmetric and racemic syntheses of heteroatom-substituted klavuzon derivatives are reported. The syntheses were completed by a well-known three-step procedure. Anti-proliferative activity of seven novel racemic klavuzon derivatives were reported against MCF-7, PC3, HCT116 p53+/+ and HCT116 p53−/− cancer cell lines. Topoisomerase I inhibitory properties of 5,6-dihydro-2H-pyran-2-one derivatives were also studied.     

过量表达GLOase导致转基因拟南芥中维生素C含量和抗逆能力提高

L-古洛糖酸-1,4-内酯氧化酶（L-gulono-1,4-lactone oxidase,GLOase）是维生素C合成途径中最后一步关键酶,小鼠（Musmusculus）编码GLOase的gulo基因转化拟南芥（Arabidopsis thaliana）的转基因株系中维生素c含量最高为5．74μmol·g^-1（FW）,是野生型的3．46倍、转p2301空载体对照的3．19倍。30％聚乙二醇（PEG-6000）模拟干旱胁迫的不同时间梯度中,幼苗期转基因拟南芥丙二醛含量低于同样处理下野生型和对照组拟南芥。不同NaCl浓度的盐胁迫下,转基因拟南芥在子叶期比野生型、对照组平均根长更长、侧根发育更好;幼苗期莲座叶长势更好、丙二醛含量更低。结果显示过量表达GLOase的转基因拟南芥在维生素c含量提高的同时,抗胁迫能力有所增强。     

Two new diterpenoids from the roots of Pygmacopremna herbacea

Two new diterpenoids, neobharangi-δ-lactone (1) and bharangi quinone (2) along with two known compounds neobharangin (3) and bharangin (4) were isolated from the ethyl acetate extract of root nodules of Pygmacopremna herbacea. The structures of the new compounds were established by 1D and 2D NMR spectroscopic data.     

粗枝崖摩中一个新的三萜

从粗枝崖摩(Amoora dasyclada (How et T.Chen)C.Y.Wu)中分离到5个化合物.通过波谱方法鉴定为:24,25-epoxy-tirucall-7-ene-3,23-dione(1),24,25,26,27-tetranortirucall-7-ene-3-oxo-23(21)-lactone(2),taraxerone(3),taraxerol(4)andβ-sitosterol(5).其中化合物1为一个新的三萜,3～5为首次从该植物中分离得到.化合物2是首次从天然植物中分离得到的一个四降三萜,对它的碳谱和氢谱数据进行了全归属.此外化合物2在碳7位上的双键和14位上的甲基并未发生变化,以前文献中没有报道过与此类似的四降三萜,据此进一步讨论了四降三萜的生物合成路径.     

Effects of lycorine on growth and effects of L-galactonic acid-gamma-lactone on ascorbic acid biosynthesis in strains of Cryptococcus laurentii isolated from Narcissus pseudonarcissus roots and bulbs

The alkaloid lycorine, which is considered to inhibit the last step in ascorbic acid biosynthesis, is produced by Narcissus pseudonarcissus. The growth of two strains (C1 and C3) of Cryptococcus laurentii isolated from root tips of N. pseudonarcissus is inhibited by lycorine, as is the in vivo production of ascorbic acid from -galactonic acid-γ-lactone. In contrast, C. laurentii strain C4, isolated from the lycorine-containing bracts of the bulb, was not inhibited by lycorine and did not contain ascorbic acid when cultivated with or without -galactonic acid-γ-lactone. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of polyhydroxy amino acids based on D- and L-alanine from D-glycero-D-gulo-heptono-1,4-lactone

2-Amino-2,3-dideoxy-D-manno-heptonic acid (7) has been synthesized from 2,5,6,7-tetra-O-acetyl-3-deoxy-D-gluco-heptono-1,4-lactone (1), which was readily prepared from D-glycero-D-gulo-heptono-1,4-lactone. O-Deacetylation of 1 followed by treatment with 13:1 (v/v) 2,2-dimethoxypropane/acetone in the presence of p-toluenesulfonic acid gave methyl 3-deoxy-4,5:6,7-di-O-isopropylidene-D-gluco-heptonate (3) as a crystalline product (80% yield). The free hydroxyl group (OH-2) of 3 was mesylated and substituted by azide to give the corresponding azide derivative 5. Hydrogenolysis and further hydrolysis of the ester function of 5 afforded alpha-amino acid 7 (43% overall yield from 1). Compound 7 is an analog of L-alanine having a polyhydroxy chain attached to C-3. The diastereoisomer of 7 at C-2, 2-amino-2,3-dideoxy-D-gluco-heptonic acid (12) was also prepared from 3, by a route that involved 2,3-dideoxy-2-iodo derivative 8 as a key intermediate.     

A new δ-lactone from the flowers of Grewia asiatica

The structure of 3, 21, 24 trimethyl-5,7-dihydroxyhentriacontanoic acid δ-lactone, a new δ-lactone, isolated from the flowers of Grewia asiatica has been deduced on the basis of physico-chemical studies.     

Synthesis and evaluation of a series of 1-(3-alkyl-2,3-dideoxy-alpha,beta-D-erythro-pentofuranosyl)thymines

A series of 1-(3-alkyl-2,3-dideoxy-alpha,beta-D-erythro-pentofuranosyl)thymines (3'-alkyl-3'-deoxythymidines) has been prepared from 5-O-(tert-butyldiphenylsilyl)-2,3-dideoxy-D-glycero-pent-2- enono-1,4-lactone ((S)-5-[(tert-butyldiphenylsilyl)oxymethyl]-2(5H)- furanone) by Michael addition of the appropriate organocopper reagent, followed by reduction of the lactone, acetylation of the resulting hemiacetal, and trimethylsilyl triflate-catalyzed coupling with 2,4-di-O-(trimethylsilyl)thymine. The protected nucleosides were desilylated by using tetrabutylammonium fluoride to give anomeric mixtures of the free nucleosides. The unsubstituted 2',3'-dideoxynucleoside analog was similarly prepared from 5-O-(tert-butyldiphenylsilyl)-2,3-dideoxy-D-glycero-pentono- 1,4-lactone ((S)5-[(tert-butyldiphenylsilyl)-oxymethyl]-dihydro-2(3H)-fu r anone).     

The application of ascorbate or its immediate precursor, galactono-1,4-lactone, does not affect the response of nitrogen-fixing pea nodules to water stress

Nitrogen fixation in legumes is dramatically inhibited by abiotic stresses, and this reduction is often associated with oxidative damage. Although ascorbate (ASC) has been firmly associated with antioxidant defence, recent studies have suggested that the functions of ASC are related primarily to developmental processes. This study examines the hypothesis that ASC is involved in alleviating the oxidative damage to nodules caused by an increase in reactive oxygen species (ROS) under water stress. The hypothesis was tested by supplying 5 mM ASC to pea plants (Pisum sativum L.) experiencing moderate water stress (ca. −1 MPa) and monitoring plant responses in relation to those experiencing the same water stress without ASC. A supply of exogenous ASC increased the nodule ASC+dehydroascorbate (DHA) pool compared to water-stressed nodules without ASC, and significantly modulated the response to water stress of the unspecific guaiacol peroxidase (EC 1.11.1.7) in leaves and nodules. However, ASC supply did not produce recovery from water stress in other nodule antioxidant enzymes, nodule carbon and nitrogen enzymes, or nitrogen fixation. The supply of the immediate ASC precursor, galactono-1,4-lactone (GL), increased the nodule ASC+DHA pool, but also failed to prevent the decline of nitrogen fixation and the reduction of carbon flux in nodules. These results suggest that ASC has a limited role in preventing the negative effects of water stress on nodule metabolism and nitrogen fixation.     

Chemical Constituents from Fruits of Rosa davidii

From the fruit of Rosa davidii Crep., eleven compounds were isolated and identified by spectral evidence, viz. 2α,3β,19β-trihydroxyl-olean-12-en-28-oic acid (1), 2α,3β-dihydroxyl-urs-28(13)-lactone (2), arjunic acid (3), euscaphic acid (4), 2α,3β-dihydroxyl-urs-12-en-28-oic acid (5), oleanolic acid (6), kaempferol (7), tiliroside (8), quercetin (9), daucosterol (10) and β-sitosterol (11). Among them, 1 and 2 were new compounds.     

Concerning the presence and formation of ascorbic acid in yeasts

The selective, sensitive method of analysis of ascorbic acid by high performance liquid chromatography with electrochemical detection (HPLC/EC) has been used to determine the ascorbic acid content of cell extracts from yeasts grown in glucose-free medium, 0.3 M D-glucose, and 0.112 M L-galactono-1,4-lactone. Saccharomyces cerevisiae (strain G-25 and its tetraploid) and a commercial baker's yeast contained less than 2 μg ascorbic acid g^?1 wet wt. of cells when grown for 22 h in glucose-free medium. In 0.3 M D-glucose, only the commercial baker's yeast gave a slight increase (2–50 μg g^?1 wet wt. in 22 h). In 0.112 M L-galactono-1,4-lactone, all three strains produced ascorbic acid (372–587 μg g^?1 wet wt. in 22 h). Lypomyces starkeyi, a species previously reported to contain a significant amount of ascorbic acid (Heick et al., Can. J. Biochem., 47 (1972) 752), was essentially devoid of ascorbic acid under all three conditions of incubation although it did contain an HPLC/EC reactive peak (R_T = 0.87 relative to ascorbic acid) that was readily oxidized by charcoal in the presence of oxygen. The identity of this new compound remains to be determined.     

Synthesis of 2,3,4,5-tetra-O-methyl-D-glucono-1,6-lactone as a monomer for the preparation of copolyesters

2,3,4,5-tetra-O-methyl-D-glucono-1,6-lactone has been prepared as a crystalline compound in acceptable yield by two different routes. An initial assay of copolymerization with L-lactide by ring-opening polymerization was carried out. The incorporation of the carbohydrate monomer into the polymer chain was about 2%.