Efficient Synthesis of (22R,23R,24S)-22,23-Isopropylidenedioxy-5α-ergost-2-en-6-one,a Key Intermediate in the Preparation of Brassinolide

(22R,23R,24S)-22,23-Isopropylidenedioxy-5α-ergost-2-en-6-one 2b is an important intermediate of brassinolide. We found that the enone 2b can be prepared by transformation of (22R,23R,24S)-3α,5-cyclo-22,23-isopropylidenedioxy-5α-ergostan-6-one 5b with catalytic amount of both p-TsOH and NaBr in DMF under reflux. 5b was prepared from (22R,23R,24S)-3α,5-cyclo-22,23-dihydroxy-6β-methoxy-5α-ergostane 9b or a 6β-benzyloxy compound 9c, which was obtained in a manner similar to Mori’s brassinolide synthesis. The enone 2b was eventually prepared via a benzyl ether 9c from stigmasterol 3a in a 15.5% yield in 11 steps.     

Brassinolide application to Lepidium sativum seeds and the effects on seedling growth

Brassinosteroids have been reported to accelerate plant growth when applied to seeds. We examined the effects of seed treatment with brassinolide on early growth of Lepidium sativum (cress). Submicromolar and micromolar concentrations of brassinolide inhibited root growth within 48 h after seed treatment. Germination of cress was not affected by brassinolide. The inhibition of cress root growth by brassinolide was time specific in terms of eliciting the response. Untreated germinated seeds transferred to filter paper moistened with brassinolide solution did not exhibit the same level of root inhibition as treated seeds. Brassinolide (2 m) had no effect on ethylene levels, suggesting that at this concentration brassinolide is acting independently of ethylene to inhibit cress root elongation. Also, brassinolide had no effect on DNA synthesis within 24 h after seed treatment, but synthesis was reduced after 48 h. The results of this study illustrate a significant specific effect on very early cress root growth by seed treatment with brassinolide.Abbreviations BR brassinosteroid(s) - SDS sodium dodecyl sulfate - TCA trichloroacetic acid - ACC 1-aminocyclopropane-1-carboxylic acid     

Synthesis of 3, 5-Di-sec-butylphenol

Synthesis of 3, 5-di-sec-butylphenol, an intermediate in the synthesis of auxin b lactone, was described. Hydrogenation of 3, 5-di-sec-butylphenol afforded 1, 3-di-sec-butylcyclo-hexane.     

Synthesis and Antimalarial Activity of Some New 1,2-Dioxolane Derivatives

The synthesis of 1,2-dioxolane derivatives in two different acetophenone series, as simplified models of natural coumarins is described. 2-Acetyl-3-acetoxy-4-(3-hydroperoxy-3-methylbut-1-enyl)phenyl acetate and 2-acetyl-5-acetoxy-4-(3-hydroperoxy-3-methylbut-1-enyl) phenyl acetate synthons are used as precursors to these structures. In vitro antimalarial activity of the 1,2-dioxolane derivatives has been investigated.     

Benzylidene acetal structural elucidation by N.M.R. Spectroscopy: Application of carbon-13. N.M.R.-Spectral parameters

The ₁₃C-n.m.r. spectra of 19 2-phenyl-1,3-dioxolane, -1,3-dioxane and -1,3-dioxopane derivatives were examined and it was found that both the ₁₃C-n.m.r. chemical shift for the acetal carbon atom and the one-bond coupling constant between the acetal carbon atom and the acetal proton had values that could be used to distinguish between acetals having different ring sizes. In addition, the presence of axial substituents at positions 4 or 6 in substituted 2-phenyl-1,3-dioxane rings and 4 or 7 in substituted 2-phenyl-1,3-dioxepane rings could be readily detected. The structures of a number of carbohydrate examples were determined by using these two parameters and also the chemical shift of the acetal proton from ₁H-n.m.r. spectra. The use of all three parameters made assignment of benzylidene acetal ring-size unambiguous.     

Accumulation and secretion of exoglucanase activity in yeast secretory mutants

Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37°C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (<65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t 1/2=150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.Non-standard abbreviations p-NPG p-nitrophenyl--d-glucopyranoside - Con A concanavalin A - Tris tris(hydroxymethyl)-amino-methane     

PHOTOSYNTHETIC PATHWAYS OF HESPERALOE FUNIFERA AND H. NOCTURNA (AGAYACEAE): NOVEL SOURCES OF SPECIALTY FIBERS

Hesperaloe funifera and H. nocturna are currently being studied as potential new sources of fibers for specialty papers. This study investigated canopy architecture and light interception in H. funifera, and gas exchange in both species. H. funifera is an acaulescent rosette species with stiff, upright leaves. Mean leaf angle for 3-year-old plants was 70° from horizontal, and more than 90% of the leaf surface was at angles greater than 50°. Vertical orientation of leaves reduced seasonal variation in light interception and midday light interception during summer months. High leaf angles are interpreted as an adaptation to arid habitats that could reduce this species' suitability for cultivation in more humid areas. Both H. funifera and H. nocturna had leaf-tissue water contents and mesophyll-succulence values intermediate between previously investigated Agavaceae known to be either C₃ or Crassulacean acid metabolism (CAM) plants. Both species proved to have CAM, however. Gas exchange characteristics varied with leaf age, with older leaves having higher assimilation rates, greater water-use efficiency, and a higher proportion of nighttime CO₂ uptake. Interestingly, these older leaves had mesophyll succulence values closer to those of typical C₃ species. These Hesperaloe species can thus be characterized as nonsucculent CAM plants. Both species showed CO₂ uptake rates of 5–8 μmol m^-2 sec^-1 expressed on a total-surface-area basis and 10–18 μmol m^-2 sec^-1 expressed on a projected-leaf-area basis. Expanded cultivation of species possessing CAM in marginal areas has been recommended recently; the physiological studies reported here along with previous studies of their economic botany identify these Hesperaloe species as good crop candidates for dry regions.     

LEAF GAS EXCHANGE IN QUERCUS MACROCARPA (FAGACEAE): RAPID STOMATAL RESPONSES TO VARIABILITY IN SUNLIGHT IN A TREE GROWTH FORM

Responses in net photosynthesis (A), stomatal conductance to water vapor (g), and leaf xylem pressure potential (ψ) were measured in the deciduous tree Quercus macrocarpa during alternating periods of sun (photosynthetic photon flux, PPF > 1,500 μmol m^-2 sec^-1) and shade (ca. 350 μmol m^-2 sec^-1 simulating cloud cover). Measurements were made on trees growing at the gallery forest-prairie edge on the Konza Prairie Research Natural Area in northeast Kansas. The region is near the westernmost extension of the range of Q. macrocarpa where this species experiences significant seasonal water stress (minimum ψ < -2.9 MPa). Quercus macrocarpa was chosen for study because it has relatively high A (15 μmol m^-2 sec^-1) and g (300 mmol m^-2 sec^-1) in contrast to the deciduous and evergreen subalpine trees previously studied. Both trees and large saplings of Q. macrocarpa responded to alternating several minute periods of sun and shade with relatively rapid changes in A and g. Reductions in g (110 mmol m^-2 sec^-1) during shade periods lowered transpirational water losses (E) by 13% (and reduced A by 5%) relative to estimates of A and E made assuming g remained constant. Partial stomatal closure during shade was correlated with moderate enhancement in ψ (0.31 MPa) in Q. macrocarpa. However, greater increases in ψ were measured in adjacent prairie grasses exposed to similar periods of shade (0.72 MPa in Andropogon gerardii, 0.61 MPa in Sorghastrum nutans). Reduced variability in ψ in tree growth forms may reflect greater buffering of water relations associated with the large size of trees, the amount of tissue devoted to water storage, and differences in hydraulic resistance relative to herbs. Nonetheless, the gas exchange and water relations responses in Q. macrocarpa were much more similar to those previously measured in herbaceous subalpine and grassland species than to those documented for subalpine trees. Thus, rapid gas exchange responses to variable PPF may also occur in tree growth forms.     

The application of toluene dioxygenase in the synthesis of acetylene-terminated resins

Summary A biotransformation procedure has been developed to prepare intermediates for the synthesis of 3-hydroxyphenylacetylene (3-HPA), a high-value specialty chemical used in the manufacture of acetylene-terminated resins. Pseudomonas putida F39/D containing toluene dioxygenase was used to oxidize a series of substituted benzenes to their respective cis-2,3-dihydroxydihydrobenzene(cis-dihydrodiol) derivatives which in turn could be converted to 3-HPA via a meta-phenol intermediate obtained by acid-catalyzed dehydration. The cis-dihydrodiols derived from the oxidation of phenylacetylene, styrene, acetophenone, and bromobenzene dehydrated to yield predominantly ortho-phenols. Three different phenyl-1,3-dioxolanes were oxidized by P. putida F39/D to three previously undescribed cis-dihydrodiols. Unlike mono-substituted cis-dihydrodiols, phenyl-1,3-dioxolane cis-dihydrodiols were dehydrated to form meta-phenols exclusively. The dehydration products, 3-hydroxyacetophenone and 3-hydroxybenzaldehyde, are suitable precursors for the chemical synthesis of 3-HPA. Offprint requests to: L. P. Wackett     

Physiological and molecular effects of brassinosteroids on Arabidopsis thaliana

We examined the effects of brassinosteroids on Arabidopsis thaliana (L.) Henyh. ecotype Columbia in order to develop a model system for studying gene regulation by plant steroids. Submicromolar concentrations of two brassinosteroids, brassinolide and 24-epibrassinolide, stimulated elongation of Arabidopsis peduncles and inhibited root elongation, respectively. Furthermore, brassinolide altered the abundance of specific in vitro translatable mRNAs from peduncles and whole plants of Arabidopsis. Root elongation in the auxin-insensitive Arabidopsis mutant axr1 was inhibited by 24-epibrassinolide but not by 2,4-D, indicating an independent mode of action for these growth regulators in this physiological response.Abbreviations BR brassinolide - EBR 24-epibrassinolide; 2.4-D,2,4-dichlorophenoxyacetic acid - KPSC 10 mM potassium phosphate, pH 6.0, 2% sucrose, 50 g/ml chloramphenicol - PAGE polyacrylamide gel electrophoresis     

Cation regulation in Anacystis nidulans

Summary Anacystis nidulans accumulates K⁺ in preference to Na⁺. The majority of the internal K⁺ exchanges with ⁴²K by a first order process at rates of about 1.3 pequiv·cm^-2·sec^-1 in the light and 0.26 pequiv·cm^-2·sec^-1 in the dark. Although the K⁺/K⁺ exchange was stimulated by light and inhibited by 10^-4 M CCCP and 10^-5 M DCMU there are several indications that this cation is passively distributed in Anacystis. Inhibition of the exchange by CCCP and DCMU occurred at concentrations greater than those required to inhibit photosynthesis and the K⁺ fluxes were stimulated by low temperatures. Moreover, although valinomycin stimulated the exchange this compound did not induce a net K⁺ leak. Assuming K⁺ is passively distributed and in free solution within the cytoplasm, as indicated by osmotic studies, would imply that there is an active Na⁺ extrusion pump operating in this organism. As yet there are no firm conclusions about the nature of the energy source for this efflux pump.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea     

Isolation and characterization of a novel 2-<Emphasis Type="Italic">sec</Emphasis>-butylphenol-degrading bacterium <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain MS-1

A novel bacterium capable of utilizing 2-sec-butylphenol as the sole carbon and energy source, Pseudomonas sp. strain MS-1, was isolated from freshwater sediment. Within 30 h, strain MS-1 completely degraded 1.5 mM 2-sec-butylphenol in basal salt medium, with concomitant cell growth. A pathway for the metabolism of 2-sec-butylphenol by strain MS-1 was proposed on the basis of the identification of 3 internal metabolites—3-sec-butylcatechol, 2-hydroxy-6-oxo-7-methylnona-2,4-dienoic acid, and 2-methylbutyric acid—by gas chromatography-mass spectrometry analysis. Strain MS-1 degraded 2-sec-butylphenol through 3-sec-butylcatechol along a meta-cleavage pathway. Degradation experiments with various alkylphenols showed that the degradability of alkylphenols by strain MS-1 depended strongly on the position (ortho ≫ meta = para) of the alkyl substitute, and that strain MS-1 could degrade 2-alkylphenols with various sized and branched alkyl chain (o-cresol, 2-ethylphenol, 2-n-propylphenol, 2-isopropylphenol, 2-sec-butylphenol, and 2-tert-butylphenol), as well as a dialkylphenol (namely, 6-tert-butyl-m-cresol).     

Castasterone is a likely end product of brassinosteroid biosynthetic pathway in rice

Brassinolide is known to be the most biologically active compound among more than 50 brassinosteroids identified to date. However, brassinolide has not been detected in rice. To determine if this is due to the lack of the brassinolide synthase function in the rice CYP85A enzyme, we performed analyses to study metabolic conversion using a yeast strain harboring the rice CYP85A1 gene. In repeated feeding tests where the substrates were used, the biosynthetic pathway progressed only up to the synthesis of castasterone, not of brassinolide. Phylogenetic analysis of the CYP85 amino acid sequences revealed that duplication of the CYP85 gene has occurred in most dicotyledonous plant genomes; further, 1 of the 2 copies of CYP85 is evolving to develop a brassinolide synthase function. However, only a single copy of this gene is found in the currently available genome sequences of graminaceous plants; this is a likely explanation for the absence of an endogenous pool of brassinolide in rice plants.     

The effect of immersion cleansers on gloss,colour and sorption of acetal denture base material

doi: 10.1111/j.1741‐2358.2012.00657.x The effect of immersion cleansers on gloss, colour and sorption of acetal denture base material Objective: To study the effect of peroxide and hypochlorite cleansers on gloss, colour and sorption of acetal denture resins. Materials and methods: Pink acetal and thermoplastic acrylic resins were evaluated. Thirty‐five specimens 39 × 39 × 1.8 mm of each resin were prepared. Each group of specimens (n = 7) was then immersed into cleansers for 100 days. Group I immersed in tap water, Group II in Corega Extradent for 5 min, Group III in Corega Extradent for 8 h, Group IV in NitrAdine? Seniors for 15 min and Group V in NaOCl 5.25%. Gloss, colour and weight measurements were taken initially and after 100 days. Data subjected to two‐way anova and Tukey’s test at α = 0.05. Results: Acrylic resin showed reductions of glossiness from ?5 to ?15 and acetal from ?0.2 to ?6. Colour changes (ΔΕ*) ranged from 2.64 to 7.64 for acrylic and 2.77 to 26.54 for acetal resin. Sorption for acrylic ranged from 11.64 to 17.06 μg/mm³ and 9.18 to 24.79 μg/mm³ for acetal resin. The results of (ΔΕ*) and sorption showed an interaction between denture resins and cleansers. Conclusions: The gloss of acetal resin was less affected by water, peroxides and NaOCl 5.25% compared with acrylic resin. Acetal resin showed clinically acceptable (ΔΕ*) whereas acrylic resin unacceptable ones for water and peroxide solutions. The immersion of acetal resin in NaOCl 5.25% showed clinically unacceptable (ΔΕ*) and higher sorption and should be avoided or should be managed with care.     

Stereoisomeric flavour compounds XLV: Structure analysis of 2-alkoxy-5-alkyl-tetrahydrofurans

The synthesis of several 2-alkoxy-5-alkyl-tetrahydrofurans is of interest in our investigations of structure–function relationships of chiral flavour compounds. For the preparation of the enantiomeric acetals the unambiguous configurational assignment of the cis and trans series of these compounds is indispensable. By means of crystalline acetal derivatives the absolute structure of a model compound in the cis and the trans configuration is revealed by X-ray measurement and correlated with the corresponding cis and trans configurated aroma compounds. The first complete structure elucidation of the class of 2-alkoxy-5-alkyltetrahydrofurans has been carried out.     

Degradation of dioxane,tetrahydrofuran and other cyclic ethers by an environmental Rhodococcus strain

Summary By enrichment and isolation techniques bacterial strains with the capacity to grow on aliphatic cyclic ethers (dioxane, tetrahydrofuran, 1,3-dioxolane) have been isolated. Six strains that degrade tetrahydrofuran were classified as belonging to the genus Rhodococcus. One of two strains that degrade dioxane instead of or in combination with tetrahydrofuran was further characterized and a hypothetical catabolic pathway comprising an initial 2-hydroxylation and several oxidation steps is postulated. Offsprint requests to: H. Diekmann     

Effect of brassinosteroids on growth and proton extrusion in the alga Chlorella vulgaris Beijerinck (Chlorophyceae)

Brassinolide, as a plant hormone, promotes growth of a number of plant species. Similar effects are induced by its epimer 24-epibrassinolide. In this paper we discuss the effects of brassinosteroids on the growth and proton extrusion in the green alga Chlorella vulgaris (Chlorophyceae). At concentrations between 10^–15 and 10^–8 m, brassinolide and 24-epibrassinolide induce a significant stimulation of growth and H⁺ extrusion. The growth was associated with an increase in the capability of algal cells to acidify the medium, where brassinolide is biologically more active than 24-epibrassinolide.Abbreviations BL brassinolide - BR(s) brassinosteroid(s) - epiBL 24-epibrassinolide - DW dry weight - IAA indole-3-acetic acid     

Azaphilones from the Fungus Penicillium multicolor LZUC-S2 and Their Antibacterial Activity

Two new azaphilones, penimultiones A and B, together with seven known analogs were isolated from the culture of Penicillium multicolor LZUC-S2. Their structures were elucidated by detailed spectroscopic data analysis and chemical transformation. Penimultiones A and B belong to a rare class of azaphilones possessing a 1,3-dioxolane moiety. In addition, all compounds were evaluated for their antibacterial activity against five clinically bacterial strains in vitro, and three compounds showed potent antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 12.5 to 50.0 μg/mL.     

Kinetic Analysis of the Inhibitory Effect of Glibenclamide on KATP Channels of Mammalian Skeletal Muscle

We investigated the block of K_ATP channels by glibenclamide in inside-out membrane patches of rat flexor digitorum brevis muscle. (1) We found that glibenclamide inhibited K_ATP channels with an apparent K _i of 63 nm and a Hill coefficient of 0.85. The inhibition of K_ATP channels by glibenclamide was unaffected by internal Mg²⁺. (2) Glibenclamide altered all kinetic parameters measured; mean open time and burst length were reduced, whereas mean closed time was increased. (3) By making the assumption that binding of glibenclamide to the sulphonylurea receptor (SUR) leads to channel closure, we have used the relation between mean open time, glibenclamide concentration and K _D to estimate binding and unbinding rate constants. We found an apparent rate constant for glibenclamide binding of 9.9 × 10⁷ m ⁻¹ sec⁻¹ and an unbinding rate of 6.26 sec⁻¹. (4) Glibenclamide is a lipophilic molecule and is likely to act on sulfonylurea receptors from within the hydrophobic phase of the cell membrane. The glibenclamide concentration within this phase will be greater than that in the aqueous solution and we have taken this into account to estimate a true binding rate constant of 1.66 × 10⁶ m ⁻¹ sec⁻¹. Received: 7 July 1996/Revised: 4 October 1996