Search

Controlling the sequence of the three consecutive reactive carbon centres of Cu-allenylidene remains a challenge. One of the impressive achievements in this area is the Cu-catalyzed annulation of 4-ethynyl benzoxazinanones, which are transformed into zwitterionic Cu-stabilized allenylidenes that are trapped by interceptors to provide the annulation products. In principle, the reaction proceeds via a preferential γ-attack, while annulation reactions via an α- or β-attack are infrequent. Herein, we describe a method for controlling the annulation mode, by the manipulation of a CF3 or CH3 substituent, to make it proceed via either a γ-attack or an α- or β-attack. The annulation of CF3-substituted substrates with sulfamate-imines furnished densely functionalized N-heterocycles with excellent enantioselectivity via a cascade of an internal β-attack and an external α-attack. CH3-variants were transformed into different heterocycles that possess a spiral skeleton, via a cascade of an internal β-attack and a hydride α-migration followed by a Diels−Alder reaction. Copper-catalysed annulation of allenylidenes provides an opportunity to target the alpha, beta, or gamma positions of the allenylidene, but achieving this control is challenging. Here substrate control allows selectivity between these three positions in the enantioselective cyclisation of ethynyl benzoxazinanones and sulfamate-derived cyclic imines.

The reduction of bis(acetylacetonato)platinum(II), nickel(II) acetate tetrahydrate and molybdenum(II) acetate dimer in a mixed solvent of oleylamine and diphenyl ether using 1,2-hexadecanediol resulted in the production of oleylamine-protected ternary alloy nanoparticles (nickel–molybdenum–platinum ternary alloy nanoparticles (NiMoPtNPs)). A ligand-exchange reaction with 50% N-methylated linear poly(ethyleneimine-co-N-methylethyleneimine) (poly(EI-co-NMEI)) in chloroform yielded poly(EI-co-NMEI)-protected NiMoPtNPs. The resultant nanoparticles had average diameters of 1.9–2.5 nm and could be dispersed in water at pH levels ranging from −1 to 14. The average radii of the NiMoPtNPs decreased when the protecting polymer was changed from oleylamine to poly(EI-co-NMEI). Energy-dispersive X-ray spectroscopy of the poly(EI-co-NMEI)-protected NiMoPtNPs was performed to confirm the formation of polymer-protected alloy nanoparticles of nickel, molybdenum and platinum. Novel nickel–molybdenum–platinum ternary alloy nanoparticles (NiMoPtNPs) stabilized by oleylamine were prepared by a hot-soap method. The following ligand-exchange reaction of oleylamine with 50% N-methylated linear poly(ethyleneimine-co-N-methylethyleneimine) (poly(EI-co-NMEI)) provided poly(EI-co-NMEI)-protected NiMoPtNPs. The average radii of poly(EI-co-NMEI)-protected NiMoPtNPs were 1.9–2.5 nm and were decreased as compared with oleylamine-protected NiMoPtNPs. Poly(EI-co-NMEI)-protected NiMoPtNPs were dispersed in methanol, ethanol and water in the range of pH −1 to 14. The energy-dispersive X-ray spectrometric analysis showed that poly(EI-co-NMEI)-protected NiMoPtNPs are a ternary metal alloy.

Platinum nanoparticles stabilized by linear polyethyleneimine (LPEI) were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The average radii of particles were 3.26 and 1.76 nm when the molecular weights of LPEI were 25 000 and 2150, respectively. These nanoparticles were well dispersed in water in the pH range of 1–6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the pH range of 0–8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the pH range of −1 to 15. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group. Platinum nanoparticles stabilized by linear polyethyleneimine (LPEI) were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The averaged radii of particles were 3.26 and 1.76 nm when the molecular weights of LPEI were 25 000 and 2150, respectively. These nanoparticles were well dispersed in water in the range of pH 1–6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the range of pH 0–8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the range of pH −1 to 15.

4,8-Dihydroxy-5-methoxy-2-naphthaldehyde (Compound I) was isolated from blackened heartwood of Diospyros kaki and was methylated with diazomethane. Antioxidant and cytotoxic activities of Compound I and two methylated derivatives [4-hydroxy-5,8-dimethoxy-2-(2-oxopropyl)-naphthalene (D-1) and 2-glycidyl-4-hydroxy-5,8-dimethoxy naphthalene (D-2)] were evaluated. Compound I showed higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and reducing power than D-1 and D-2. However, D-1 and D-2 exhibited slightly stronger 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)+ (ABTS+) radical scavenging activity than Compound I. Compound I also exhibited stronger cytotoxic activity than D-1 and D-2 against the growth of HT-29 colon cancer cells. The results supported the hypothesis that methylation of naphthalene derivatives slightly increased ABTS+ radical scavenging activity, but significantly decreased DPPH radical scavenging activity, reducing power, and cytotoxic activity.

A detailed chemical investigation of the extractives of the blackened heartwood of Diospyros kaki was carried out to understand their chemical characteristics and to obtain chemotaxonomic information. Three novel naphthalene derivatives were isolated, i.e., 4-hydroxy-5,6-dimethoxy-2-naphthaldehyde (1), 5,6,8-trimethoxy-3-methyl-1-naphthol (2), and 4,8-dihydroxy-5-methoxy-2-naphthaldehyde (3), in addition to two previously reported 2-naphthaldehydes: 4-hydroxy-5,8-dimethoxy-2-naphthaldehyde (4) and 4-hydroxy-5-methoxy-2-naphthaldehyde (5) Their structures were identified by 1D and 2D nuclear magnetic resonance spectroscopy, as well as by high-resolution mass spectrometry.

Heartwood extracts from Amazonian trees cumaru-ferro (Dipteryx odorata), jatoba (Hymenaea courbaril), and guarita (Astronium lecointei) exhibit antioxidant activities comparable with that of α-tocopherol, a well-known antioxidant. This article reports the characterization of the antioxidant compounds in the extracts of the three heartwoods. Silica gel column chromatography of the cumaru-ferro EtOAc extract yielded (−)-(3R)-7,2′,3′-trihydroxy-4′-methoxyisoflavan and (+)-(3R)-8,2′,3′-trihydroxy-7,4′-dimethoxyisoflavan. Silica gel column chromatography followed by preparative high-performance liquid chromatography of the jatoba EtOAc extract yielded (−)-fisetinidol and (+)-trans-taxifolin. Chemical structures were assigned using electron-ionization mass spectrometry, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy including nuclear Overhauser effect spectroscopy (NOESY), as well as optical rotation and circular dichroism. Gas chromatography-mass spectrometry demonstrated that the isolated compounds were predominant in the EtOAc extracts. In the guarita EtOAc extract, catechin and gallic acid were identified by comparing their retention times and mass fragmentation patterns with those of authentic samples. Antioxidant activity determined by the 1,1-diphenyl-2-picrylhydrazyl assay demonstrated that all these compounds had activities comparable with that of α-tocopherol.

The heartwood and sapwood characteristics of 11 Amazonian trees were investigated. Whereas 7 of the specimens had densities greater than 0.7 g/cm3, the heartwood density of ipe amarelo (Tabebuia serratifolia), macaranduba (Manilkara huberi), cumaru-ferro (Dipteryx odorata), and guarita (Astronium lecointei) exceeded 1.0 g/cm3. Jatoba contained small amounts of Klason lignin and α-cellulose, and large amounts of holocellulose and alkali extract, suggesting that it has a high polysaccharide content that can be dissolved in an alkaline medium. The difference in the syringyl/guaiacyl (S/G) ratios of the samples before and after alkali extraction suggests that alkali extracts contain syringyl-type polyphenols. In all of the samples, the heart-wood methanol extracts were larger in volume than the sapwood methanol extracts, and the sapwood alkali extracts were larger in volume than the heartwood alkali extracts. The antioxidant activities of the methanol and alkali extracts were assayed by measuring the levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and super oxide dismutase (SOD)-like activity, respectively. The heart-wood methanol extract of jatoba (Hymenaea courbaril) exhibited the highest level of activity (EC50 = 44 mg/l), which exceeded that of α-tocopherol (EC50 = 48 mg/l), and the heartwood alkali extracts of jatoba and ipe amarelo had high SOD-like activity comparable with red wine.

To study the behavior of hardwood sulfuric acid lignin (SAL) during phenolization, we compared the product yield, average molecular weight, methoxy content, and reactions of simple model compounds with those of softwood SAL, focusing on the difference between syringyl and guaiacyl units. The beech SAL reacted with phenol more readily than red pine SAL and yielded a larger soluble fraction of phenolized SAL. To investigate the difference in the phenolization activity of the syringyl and guaiacyl units in beech lignin, we prepared syringyl-nucleus-rich sulfuric acid lignin (S-rich-SAL) and guaiacyl-nucleus-rich sulfuric acid lignin (G-rich-SAL) from beech, which were subjected to phenolization. The results suggest that the syringyl unit in SAL had greater phenolization activity and its phenolized products were more soluble in acidic aqueous medium and introduced less phenol than the guaiacyl unit. Using model compounds, the study also showed that the syringyl unit had higher phenolization reactivity than the guaiacyl unit.

We investigated the relationship between turgor pressure and diurnal differences in secondary wall formation of differentiating tracheids. Saplings of Cryptomeria japonica were grown in a growth chamber with 12-h light:12-h dark cycles, and the tangential strain on the inner bark surface was measured as an indicator of the volumetric changes of differentiating cells. The innermost surface of developing secondary walls was then observed using field emission scanning electron microscopy at 1-h intervals after both light and dark periods. Dramatic changes in the aspects of the innermost surface of developing secondary walls occurred 3h after the light was switched on and 4h after the light was switched off. The amorphous material containing glucomannans became evident when the differentiating cells became fully turgid during the dark period. Conversely, cellulose microfibrils became clearly visible when the cell volume was low during the light period. These results suggest that the diurnal periodicity in the supply of hemicellulose-containing matrix to developing secondary walls is associated with the changes in turgor pressure of differentiating tracheids that result from the change in light conditions during the photoperiodic cycle.

To establish an experimental approach for studying the biosynthetic pathway of agatharesinol, a norlignan, induction of the formation of agatharesinol in Cryptomeria japonica (Japanese cedar, sugi) was attempted. Wood sticks were prepared from the sapwood immediately after cutting a sugi tree down, and they were allowed to stand in desiccators in which the humidity was adjusted to 76% and 88%, and in a room. When the wood sticks were allowed to stand in 76% humidity and in a room, they dried rapidly and no formation of agatharesinol was demonstrated by gas chromatography-mass spectrometry. These results suggest that in the sapwood dried rapidly, the cells that were biologically active in the sapwood, probably ray parenchyma cells, die rapidly and completely before the biosyntheses of secondary metabolites including agatharesinol was wholly established. The wood sticks allowed to stand in 88% humidity, on the other hand, dried gradually compared with the sticks placed in 76% humidity and in a room, and agatharesinol was formed as one of the predominant ethyl acetate extractives. These results suggest that delaying the drying of the sapwood sticks can control the dying period to an appropriate length for the ray parenchyma cells, during which the biosynthesis of agatharesinol is induced.

This article describes the effect of day length during the photoperiodic cycle on the diurnal differences in the innermost surface of developing secondary walls. Saplings of Cryptomeria japonica D. Don. were grown in growth chambers at constant temperature and relative humidity, but with different photoperiods. Samples of differentiating xylem were collected during the light and dark periods. The innermost surface of developing secondary walls in differentiating tracheids were observed using field emission scanning electron microscopy, and observations made during the light and dark periods were compared. In the saplings grown under long-day or short-day conditions, diurnal differences in aspects of the innermost surface of developing secondary walls were observed. Cellulose microfibrils were observed on the innermost surface of developing secondary walls during the light period when the volumes of differentiating cells were low, and amorphous material was observed during the dark period, when differentiating tracheids were turgid. The amorphous material was labeled with antiglucomannan antiserum. These results suggest that the range of day-length conditions set in this study does not affect the diurnal periodicity in the supply of cell wall components to the innermost surface of developing secondary walls.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was applied to the investigation of heartwood extractives in Sugi (Cryptomeria japonica). Sugi heartwood tissue generated secondary ions that were not produced from sapwood tissue by TOF-SIMS. Among the peculiar ions generated from heartwood, two positive ions of m/z 285 and 301 were remarkable due to their appearance in a larger mass range and with a high intensity. These two ions were not generated from heartwood tissue preextracted with n-hexane, and the n-hexane extract of Sugi heartwood produced both ions. Gas chromatography-mass spectrometry of the n-hexane extract demonstrated that ferruginol, a diterpene phenol, the molecular weight of which is 286, constituted one of the predominant constituents of the extract. Authentic ferruginol also generated both ions by TOF-SIMS. The molecular formula of the m/z 285 ion generated from Sugi heartwood tissue was estimated to be C(20)H(29)O, which corresponds well with that of ferruginol, i.e. C(20)H(30)O, by peak identification. All these results strongly suggest that the m/z 285 ion generated from Sugi heartwood tissue originated significantly from ferruginol in Sugi heartwood. By TOF-SIMS imaging, the m/z 285 ion was detected uniformly in the tracheid cell walls, in the cell walls of the axial parenchyma cells and ray parenchyma cells, and also inside these parenchyma cells. These results indicate that ferruginol was distributed almost evenly in Sugi heartwood tissue.

The reactivity of previously prepared antiserum against agatharesinol, a norlignan, was determined by competitive inhibition–ELISA (enzyme-linked immunosorbent assay) using several natural compounds that are representative of plant extractives as competitive inhibitors. The antiserum strongly reacted with some norlignans (i.e., agatharesinol, hinokiresinol, and metasequirin C), each of which has a common chemical-structural unit. This result suggests that the antiserum recognizes the specific chemical-structural unit composing those norlignans. Moreover, differences in the reactivities of the antiserum with agatharesinol derivatives and synthetic chalcones propose the trans-3-p-hydroxyphenyl-1-phenylpropene structural unit as the major antigenic determinant for the antiserum.

To radiolabel xylan in mature cell walls selectively, magnolia (Magnolia kobus DC.) was administered withmyo-inositol-[2-3H] and allowed to metabolize for 1 month. The radiolabeled xylem tissue was then submitted to sulfuric acid hydrolysis and nitrobenzene oxidation. A large amount of radioactivity was found mainly in xylose, although slight activities were detected in glucose and in vanillin and syringaldehyde. The labeled tissue was submitted to a preparation of holocellulose followed by treatment with 24% potassium hydroxide (KOH). Radioactivity was distributed mainly in the KOH-soluble part of the holocellulose. These results indicate that most radioactivity was incorporated into xylan in the cell walls. The distribution of the incorporated radioactivity in the xylem tissue was visualized by microautoradiography. Radioactivities were distributed in the xylem more than 400 μm from the cambium; and an inner layer of a secondary wall had formed at the labeled xylem. Consequently, selective radio-labeling of xylan was visualized in mature cell walls.

myo-Inositol-[2-3H] and d-glucuronic acid-[6-14C] were administered simultaneously to a growing stem of magnolia (Magnolia kobus DC) to label xylan and pectin, respectively, in the cell wall. Determination of the radioactivity of nitrobenzene oxidation products and sulfuric acid hydrolysates of the newly formed xylem indicated that xylan and pectin were labeled with 3H and 14C, respectively. The doubly labeled wood tissue was treated to kraft pulping, and the radioactivity of the pulping black liquor and treated wood tissue were determined at various stages of the pulping to compare the dissolving behavior between pectin and xylan during the pulping. The results showed that pectin was not dissolved as easily as xylan and was not redeposited on pulp fiber at the late stage of the pulping.

Highly condensed lignin can be transformed by three reactions — phenolation, hydroxymethylation, and neutral sulfonation — to water-soluble lignosulfonate. To elucidate reactivities and products in the latter two reactions, simple compounds were selected as lignin model compounds. With hydroxymethylation of creosol at 60°C, the yield of a condensed-type product with the diarylmethane structure was less than 10%. Hydroxymethylation of 1-guaiacyl-1-p-hydroxy-phenylethane (compound VI) as a phenolized guaiacyl lignin model compound gave four compounds. The initial reaction introduced the hydroxymethyl group mainly in the guaiacyl nucleus, and the additional reaction created two hydroxymethyl groups in the p-hydroxyphenyl nucleus. Contrary to our estimation, treatment of the models with 13C-labeled formaldehyde (H13CIIO) did not form any diarylmethane structure. Neutral sulfite treatment of hydroxymethylated products gave corresponding sulfonates in high yields. Phenolized guaiacylglycerol-β-aryl ether (compound XVI) showed a reactivity similar to that of compound VI.

• Introduction In Cryptomeria japonica, heartwood properties are considered to be affected by specific extractives. It remains unclear whether traits of specific heartwood compounds are under genetic control.

During manufacture of plywood from yellow meranti (Shorea spp.) collected in Sarawak, the extractives stick on press boards and on plywood panels in some cases. The stuck material is phenolic and has low solubility in organic and inorganic solvents. Investigation of the methanol extracts of yellow meranti wood suggested that the material is a mixture of biosynthetic compounds and/or their secondary oxidative polymers of resveratrol and its related stilbenes.