A Stereoselective Synthesis of Antimycinone A3 and Its Stereoisomers

Antimycinone A₃, which is a neutral fragment of mild alkaline hydrolysate of antimycin A₃, and its stereoisomers were synthesized stereoselectively from methyl trans-2-n-butylpent-3-enoate or methyl cis-2-n-butylpent-3-enoate, and natural antimycinone A₃ was proved to possess Hα-Hβ and Hβ-Hγ trans configuration.     

Studies on Abscisic Acid

Oxidation of methvl 2-trans-β-ionylideneacetate with X-bromosuccinimide afforded methyl 2-cis and trans-3′-hydroxy-β-ionylideneacetates. NaBH₄ reduction of methyl 2-cis-3′-keto-β-ionylideneacetate and ethyl 4′-keto-α-ionylideneacetate gave methyl 2-cis-3′-hydroxy-β-ionylideneacetate and ethyl 4′-hydroxy-α-ionyiideneacetate respectively. Further, methyl 4′-methoxy-epoxy-α-ionylideneacetate was prepared by epoxidation of methyl 4′-methoxy-α-ionylideneacetate. And then methyl 4′-hydroxy-l′, 2′-dihydro-β-ionylideneacetate was synthesized from ethyl 4-keto-α-cyclogeranate. Growth inhibitory activities of the above compounds on rich seedlings were examined.     

Minor Constituents of Japanese Ho-Leaf Oil

The main component of Japanese Ho-leaf oil has been shown to be (?)-linalool (80~90%), and the following twenty minor constituents newly have been identified; methyl vinyl ketone, methyl isobutyl ketone, mesityl oxide, β-pinene, myrcene, (+)-limonene, cis- and trans-ocimene, n-hexanol, cis-3-hexenol, cis- and trans-linalool oxide, (?)-1-terpinen-4-ol, (+)-cis and (+)-trans-2,6,6-trimethyl-2-vinyl-5-hydroxytetrahydropyran, citronellol, nerol, (+)-β-selinene, (+)-tagetonol and (?)-trans-hotrienol. (+)-Tagetonol and (?)-trans-hotrienol have been demonstrated to be (+)-3,7-dimethyl-3-hydroxy-1-octen-5-one (III) and (3R)-(?)-trans-3,7-dimethyl-3-hydroxy-1,5,7-octatriene (IX), respectively.     

Studies on Abscisic Acid

Methyl α-ionylideneacetates were oxidized with selenium dioxide to a mixture of methyl 3′-keto-β-ionylideneacetates and a small amount of methyl 4′-keto-α-ionylidene-acetates followed by treatment with active manganese dioxide. By a similar oxidation methyl 3′-keto-β-ionylideneacetates were prepared from methyl β-ionylidene acetates. Methyl 4′-keto-α-ionylideneacetates were obtained by oxidation of methyl α-ionylideneacetates with tert-butyl chromate. Dehydrobromination of methyl bromoionylideneacetate, obtained by bromination of methyl 2-trans-α-ionylideneacetate with N-bromosuccinimide, gave a mixture of methyl 2-trans-dehydro-β-ionylideneacetate and methyl 2-cis-dehydro-β-ionylideneacetate. The growth inhibitory activities of these sesquiterpene carboxylic acids and keto esters on rice seedlings were tested.     

Conversion of Farnesol into Methyl dl-12-Homo-10-trans-juvenate,the 10-trans-lsomer of dl-C17-Cecropia Juvenile Hormone

Methyl dl-12-homo-10-trans-juvenate (III) was synthesized from farnesol (IV) in eight steps involving stereoselective conversion of the trans-terminal methyl group to an ethyl group. The product (III) was less active than dl-C₁₇-Cecropia juvenile hormone on both Tenebrio molitor and Galleria mellonella.     

Induction of pumpkin glutathione S-transferases by different stresses and its possible mechanisms

Induction of pumpkin (Cucurbita maxima Duch.) glutathione S-transferases (GSTs) by different stresses and endogenous trans-2-hexenal content were determined in search of a common signal for GST induction. All of the stresses showed significant induction, As₂O₃ causing the highest induction followed by trans-2-hexenal. The trans-2-hexenal content was highest in trans-2-hexenal-treated seedlings and next-highest in methyl jasmonate-treated seedlings, whereas high temperature- and As₂O₃-treated seedlings had trans-2-hexenal contents lower than that of control seedlings. Induction of GST, lipoxygenase (LOX) and hydroperoxide lyase (HPL) was compared, since trans-2-hexenal and methyl jasmonate are the products of the LOX pathway. All four stresses showed weak LOX induction, high temperature causing the highest induction. However, only methyl jasmonate caused weak HPL induction. Both antioxidants or oxidants induced GST to different degrees. Glutathione contents of reduced glutathione (GSH) or oxidized glutathione (GSSG)-treated seedlings were significantly higher than the content of control seedlings, whereas those treated with other antioxidants or oxidants had contents similar to or less than control seedlings. The GSH:GSSG ratio was lowest in GSSG-treated seedlings and next-lowest in GSH-treated seedlings. The results of this study suggest that pumpkin GSTs are not induced through a common signalling pathway and that redox perturbation plays a role in pumpkin GST induction.     

Studies on Chrysanthemic Acid

Synthesis of (±)-trans-chrysanthemic acid from (±)-1′-hydroxydihydro-trans-chrysanthemic acid by the dehydration with p-toluene-sulfonic acid was attempted. However, the attempt was found to be unsuccessful giving a compound believed to be methyl methyl 2,6 dimethylhepta-3.6-diene-5-carboxylate upon dehydration.

A cleavage upon cyclopropane ring was confirmed by deriving the acid obtained by the hydrolysis of the above ester to already known 2,6-dimethyl-heptane-5-carboxylic acid.

Analogous mode of dehydration and cleavage upon the ester of (±)-2,2-dimethyl-3-trans-hydroxylbenzyl-cyclopropane-l-carboxylic acid was also observed to give 1-phenyl-4-methyl-penta-1,3-diene-3-carboxylic acid. On the other hand, (±)-trans-caronic acid being derived to (±)-1′-oxo-2′-hydroxy-dihydro-trans-chrysanthemic acid, the synthesis of (±)-trans-chrysanthemic acid from (±)-trans-caronic acid became possible using (±)-1′-oxo-2′-hydroxy-dihydro-trans-chrysanthemic acid as a relay substance.     

Stereospecific assignments of 1H-nmr methyl lines and conformation of valyl residues in the lac repressor headpiece

Two-dimensional ¹H-nmr methods are described to obtain information on the sidechain conformation of valyl residues of the lac repressor headpiece and to assign the resonances of their methyl groups stereospecifically. The spin–spin coupling constants (J_αβ) between C^αand C^β protons are obtained from two-dimensional correlated spectroscopy experiments. Large values for J_αβ(10–12 Hz) corresponding to trans orientations for these protons (g⁺ conformation) are found for all valyl residues in α-helical segments. For these valyl residues, the distance between one methyl group (γ₁)and the valyl amide proton is much shorter than for the other methyl group, so that stereospecific resonance assignments follow from relative intensities of the corresponding cross peaks in a two-dimensional nuclear Overhauser enhancement spectrum. Thus, streospecific assignments could be made for the methyl groups of Val 9, 20, 23, and 38 (of a total of eight valyl residues).     

Studies on Abscisic Acid

Oxidation of 2-cis-α-ionylidene-ethanol (II) with active MnO₂ afforded a mixture of 2-cis and 2-trans-α-ionylideneacetaldehydes (III and IV). Reduction of methyl epoxy-α- and -β-ionylideneacetates (Vb, Xb XXIb and XXIIb) with LiAlH₄ gave the diols (VI, XI, XXIII and XXIV). The Wittig reaction of the hydroxyketones (XIII and XVIII) with carbethoxymethylenetriphenylphosphorane, followed by alkaline hydrolysis, yielded 5-(1′-and 2′-hydroxy-2′,6′,6′-trimethyl-1′-cyclohexyl)-3-methylpentadienoic acids (XIVa, XVa, XIXa and XXa). The reaction of α-cyclocitrylideneacetaldehyde (XXVII) and dihydro-α-ionone (XXXIII) with carbethoxymethylenetriphenylphosphorane afforded ethyl 3-demethyl-α-ionyli-deneacetate (XXVIIIb) and ethyl dihydro-α-ionylideneacetates (XXXIVb and XXXVb). Physiological activities of the above synthesized compounds on rice seedlings were examined.     

Microbial Allyl Rearrangement and Resolution of Acetates of Unsaturated Cyclic Terpene Alchols by Pseudomonas sp. NOF-5 Strain

Microbial hydrolysis of the acetates of unsaturated cyclic terpene alcohols by Pseudomonas sp. NOF-5 isolated from soil was investigated. (±)-trans-Carveyl acetate ((±)-trans-3) was enantio-selectively hydrolyzed with NOF-5 strain to give ( – )-trans-carveol (( – )-trans-2 of 86.6% optical purity). However, the hydrolysis of (±)-cis-3 was less enantioselective, while (±)-piperitylacetate ((±)-6, a cis and trans mixture) was hydrolyzed to give the ( – )-trans- and ( – )-cis-piperitols (( – )- trans-5 and ( – )-cis-5) in a poor optical yield. In this case, other tert-alcohols, ( + )-trans- and ( – )- ds-2-p-menthen-1-ols ((±)-trans-7 and ( – )-cis-7), were also produced. Furthermore, microbial and enzymic allyl rearrangements of ( + )-trans-6 and ( – )-trans-verbenylacetate (( – )-trans-11) were studied. Biological treatment of (+)-trans-6 and ( – )-trans-11 with NOF-5 or its esterase gave (+)-trans- and (-)-cis-1 and ( + )-cis-3-pinen-2-ol (( + )-cis-12), respectively.     

Proton and phosphorus NMR studies of d-CpG(pCpG)n duplexes in solution. Helix-coil transition and complex formation with actinomycin-D.

The Watson–Crick imino and amino exchangeable protons, the nonexchangeable base and sugar protons, and the backbone phosphates for d-CpG(pCpG)_n, n = 1 and 2, have been monitored by high-resolution nmr spectroscopy in aqueous solution over the temperature range 0°–90°C. The temperature dependence of the chemical shifts of the tetramer and hexamer resonances is consistent with the formation of stable duplexes at low temperature in solution. Comparison of the spectral characteristics of the tetranucleotide with those of the hexanucleotide with temperature permits the differentiation and assignment of the cytosine proton resonances on base pairs located at the end of the helix from those in an interior position. There is fraying at the terminal base pairs in the tetranucleotide and hexanucleotide duplexes. The Watson–Crick ring imino protons exchange at a faster rate than the Watson–Crick side-chain amino protons, with exchange occurring by transient opening of the double helix. The structure of the d-CpG(pCpG)_n double helices has been probed by proton relaxation time measurements, sugar proton coupling constants, and the proton chemical shift changes associated with the helix–coil transition. The experimental data support a structural model in solution, which incorporates an anti conformation about the glycosyl bonds, C(3) exo sugar ring pucker, and base overlap geometries similar to the B-DNA helix. Rotational correlation times of 1.7 and 0.9 × 10^?9 sec have been computed for the hexanucleotide and tetranucleotide duplexes in 0.1 M salt, D₂O, pH 6.25 at 27°C. The well-resolved ³¹P resonances for the internucleotide phosphates of the tetramer and hexamer sequences at superconducting fields shift upfield by 0.2–0.5 ppm on helix formation. These shifts reflect a conformational change about the ω,ω′ phosphodiester bonds from gauche-gauche in the duplex structure to a distribution of gauche-trans states in the coil structure. Significant differences are observed in the transition width and midpoint of the chemical shift versus temperature profiles plotted in differentiated form for the various base and sugar proton and internucleotide phosphorous resonances monitoring the d-CpG(pCpG)_n helix–coil transition. The twofold symmetry of the d-CpGpCpG duplex is removed on complex formation with the antibiotic actinomycin-D. Two phosphorous resonances are shifted downfield by ～2.6 ppm and ～1.6 ppm on formation of the 1:2 Act-D:d-CpGpCpG complex in solution. Model studies on binding of the antibiotic to dinucleotides of varying sequence indicate that intercalation of the actinomycin-D occurs at the GpC site in the d-CpGpCpG duplex and that the magnitude of the downfield shifts reflects strain at the O-P-O backbone angles and hydrogen bonding between the phenoxazone and the phosphate oxygens. Actinomycin-D is known to bind to nucleic acids that exhibit a B-DNA conformation; this suggests that the d-CpG(pCpG)_n duplexes exhibit a B-DNA conformation in solution.     

Synthesis of esters of saturated and unsaturated sixteen-carbon acids deuterated at the terminal or penultimate carbons

General syntheses of saturated and unsaturated fatty acids, specifically trideuterated at the terminal carbon or dideuterated at the penultimate carbon, from ω-hydroxy esters, have been developed. Methyl [16-²H₃]hexadecanoate was synthesized from methyl 16-hydroxyhexadecanoate. The hydroxyl group was protected as the tetrahydropyranyl ether and the ester group reduced with lithium aluminum deuteride, first to an alcohol and then, by way of the derived mesylate, to a trideuteromethyl group. The new ester group was formed by oxidation of the hydroxyl group. Methyl 16-hydroxy[2-²H₂]hexadecanoate was prepared, from 16-hydroxy-hexadecanoate, by exchange of the α protons and, by the reductive route above, with lithium aluminum hydride, gave methyl [15-²H₂]hexadecanoate. Methyl 16-hydroxy-7-hexadecynoate was synthesized from 6-chlorohexanol and was converted, by means of the above reactions, to methyl [16-²H₃]- and [15-²H₂]-9-hexadecynoates. Lindlar reduction gave methyl [16-²H₃]- and [15-²H₂]cis-9-hexadecenoates. Overall yields ranged from 30% to 38%.     

Biosynthesis of methyl chloride in the fungusPhellinus pomaceus

The biosynthetic origin of themethyl group in the methyl chloride produced by cultures ofPhellinus pomaceus (Pers.) Maire has been investigated using stable isotope labeled substrates. Feeding ofd-[6,6-²H₂] glucose,Dl-[3,3-²H₂] serine andl-[methyl-²H₃] methionine led to the production of deuterated methyl chloride in which the major labeled species contained 2, 2, and 3 deuterium atoms, respectively. The data are consistent with the methyl chloride produced by this organism being derived solely from methionine with retention of all of the methyl protons.Abbreviation SAM S-adenosylmethionine - FH₄ tetrahydrofolate - N⁵-CH₃FH₄ N⁵-methyltetrahydrofolate - B₁₂ cobalamin     

Pentalenene biosynthesis and the enzymatic cyclization of farnesyl pyrophosphate: Proof that the cyclization is catalyzed by a single enzyme

A cell-free preparation from Streptomyces UC5319 has been developed which catalyzes the conversion of trans, trans-farnesyl pyrophosphate (1) to pentalenene (2), the parent hydrocarbon of the pentalenolactone family of sesquiterpene antibiotics. Incubation of [9-³H₂, 12,13-¹⁴C]farnesyl pyrophosphate with the pentalenene synthetase gave [1,8-³H₂, 14,15-¹⁴C]pentalenene, as established by a combination of chemical and microbial degradation methods. The retention of both equivalents of tritium in the enzymatically derived pentalenene establishes that the cyclization of trans, trans-farnesyl pyrophosphate to 2 is catalyzed by a single enzyme.     

Ribonucleic Acid Metabolism in Germinating Soybeans

A stereoselective synthesis of methyl trans, trans-farnesoate (I) from isoprenyl bromide and geraniol is described. dl-C₁₇-Cecropia juvenile hormone (IV) was synthesized from it in a stereoselective manner.     

High-performance liquid chromatography of p-nitrophenacyl esters of selected prostaglandins on silver ion-loaded microparticulate cation-exchange resin

A silver ion-loaded microparticulate cation-exchange resin column has been used for high-performance liquid chromatographic (HPLC) separation of the p-nitrophenacyl esters of several series of closely related prostaglandins: 8-iso-PGE₂, 11-epi-PGE₂, 5-trans-PGE₂, PGE₂, PGF_1α, PGE₁, and PGF_2α, PGA₂ and PGB₂; 15 (R)-methyl-PGE₂ and 15 (S)-methyl-PGE₂; 5-trans-PGA₂ and PGA₂; and 5-trans-PGF_2α and PGF_2α. The properties of this column are compared with those of silica-gel and reversed-phase columns.     

Three Previously Undescribed Chlorophenyl Glycosides from the Bulbs of Lilium regale

Three previously undescribed chlorophenyl glycosides, (2,4,6-trichloro-3-hydroxy-5-methoxyphenyl)methyl β-D-glucopyranoside ( 1 ), (2,4-dichloro-3,5-dimethoxyphenyl)methyl 6-O-β-D-glucopyranosyl-β-D-glucopyranoside ( 2 ) and 4-chloro-3-methoxy-5-methylphenyl 6-O-(6-deoxy-β-L-mannopyranosyl)-β-D-glucopyranoside ( 3 ) were obtained from Lilium regale. The absolute configurations of these new finds were elucidated by comprehensive analyses of spectroscopic data combined with acid hydrolysis derivatization. (2,4-dichloro-3,5-dimethoxyphenyl)methyl 6-O-β-D-glucopyranosyl-β-D-glucopyranoside ( 2 ) can inhibit the proliferation of lung carcinoma A549 cells with an IC₅₀ value of 29 μΜ.     

Simultaneous CT-13C and VT-15N chemical shift labelling: Application to 3D NOESY-CH3NH and 3D 13C,15N HSQC-NOESY-CH3NH

Based on the HSQC scheme, we have designed a 2D heterocorrelated experiment which combines constant time (CT) ¹³C and variable time (VT) ¹⁵N chemical shift labelling. Although applicable to all carbons, this mode is particularly suitable for simultaneous recording of methyl-carbon and nitrogen chemical shifts at high digital resolution. The methyl carbon magnetisation is in the transverse plane during the whole CT period (1/J_CC=28.6 ms). The magnetisation originating from NH protons is initially stored in the 2H_zN_z state, then prior to the VT chemical shift labelling period is converted into 2H_zN_y coherence. The VT -¹⁵N mode eliminates the effect of ¹ J _N,CO and ^1,2 J _N,CA coupling constants without the need for band-selective carbon pulses. An optional editing procedure is incorporated which eliminates signals from CH₂ groups, thus removing any potential overlap with the CH₃ signals. The CT-¹³CH₃,VT-¹⁵N HSQC building block is used to construct two 3D experiments: 3D NOESY-CH₃NH and 3D ¹³C,¹⁵N HSQC-NOESY-CH₃NH. Combined use of these experiments yields proton and heteronuclear chemical shifts for moieties experiencing NOEs with CH₃ and NH protons. These NOE interactions are resolved as a consequence of the high digital resolution in the carbon and nitrogen chemical shifts of CH₃ and NH groups, respectively. The techniques are illustrated using a double labelled sample of the CH domain from calponin.     

Volatile oil constituents of sagebrush

The volatile oil of Artemisia arbuscula arbuscula contained a new irregular monoterpene, 2,5-dimethyl-4-vinyl-1,5-hexadiene-3-ol (isolyratol), which was isolated and identified by spectral means. The optically pure furanoid (2S,5S)-trans-5-methyl-5-vinyltetrahydrofur-2-yl methyl ketone (arbusculone), was also characterized by transformation to known (2S,5S)-trans-linalyl oxide. The former component has never been isolated from natural sources prior to this study. The neutral pentane extract also contained several previously characterized non-head-to-tail monoterpenes including artemiseole, artemisia ketone, artemisyl acetate, methyl santolinate, and santolina triene, as well as the regular monoterpenes 1,8-cineole, camphor, p-cymene, camphene and the C₆ fragment, terelactone.     

Novel Antioxidants Isolated from Perilla frutescens Britton var. crispa (Thunb.)

Two novel antioxidants (vinyl caffeate and trans-p-menth-8-en-7-yl caffeate) and seven known antioxidants (3,4-dihydroxybenzaldehyde, methyl 3,4-dihydroxy-benzoate, methyl caffeate, 3′,4′,5,7-tetra-hydroxy-flavone, caffeic acid, 6,7-dihydroxycoumarin, and rosmarinic acid) were isolated from Perilla frutescens Britton var. crispa (Thunb.). The redox potentials of the novel isolated antioxidative compounds were comparable to those of known antioxidants. trans-p-menth-8-en-7-yl caffeate was effective to prevent the oxidative degradation of perillaldehyde in the essential oil of P. frutescens.