The preparation and properties of a stable mercury derivative of transfer RNAs from Escherichia coli

Further investigations into the properties of the mercury derivative formed by the reaction of 4-thiouridine-containing tRNAs and pentafluorophenylmercury chloride have been carried out. tRNA^fMet (which contains only one 4-thiouridine residue) has been isolated by a one-step column Chromatographic procedure from unfractionated Escherichia coli tRNA and has been shown to react with the mercury compound to give a derivative which has similar properties to those previously reported for the corresponding mercury derivative of tRNA^Tyr which contains two adjacent 4-thiouridine residues. The mercury derivative of tRNA^Tyr appears to be a competitive inhibitor of tRNA^Tyr in the aminoacylation reaction (tRNA^TyrK_m = 0.42 μM, mercury derivative of tRNA^TyrK_i = 0.11 μM). The mercury derivative of Tyr-tRNA^Tyr can be made, but only by the reaction of the mercury compound with the aminoacylated tRNA.     

Chemical modification of chitosan under high-intensity ultrasound and properties of chitosan derivatives

Chitosan (CTS), a biocompatible, biodegradable, nontoxic polymer, shows poor affinity for organic solvents. A novel chitosan derivative carrying the p-acetamidobenzoylate group was synthesized by the acylation reaction of chitosan with p-acetamidobenzoylate chloride in an acetic acid system under high-intensity ultrasound. The maximum substitution degree of the derivative was 0.42. The structure of the p-acetamidobenzoylate chitosan was characterized by FT-IR spectrometry, UV spectrometry and elemental analysis. The UV results showed that the derivative had good ultraviolet absorption at 273 nm. The solubility of the derivative was higher than that of chitosan. Taking advantage of the known capacity of solubility and ultraviolet absorption, the new derivative opens new possibilities for use as a sunscreen.     

A physico-chemical and biological study of novel chitosan-chloroquinoline derivative for biomedical applications

This paper describes an elegant cross-linking technique for the preparation of chitosan-chloroquinoline derivative by using a greener technique. Chitosan solution in aqueous acetic acid was treated with 2-chloroquinoline-3-carbaldehyde solution to form hydrogel; the resulting hydrogel was subjected to solvent exchange. Combining the results of FTIR and XRD confirmed that 2-chloroquinoline-3-carbaldehyde have been reacted to chitosan. The morphology of the derivative was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of the derivative was examined by thermogravimetric analysis (TGA). The photoluminescence (PL) spectra of chitosan-chloroquinoline derivative show red-shifted emission maximum. The microbiological screening has demonstrated the antimicrobial activity of the derivative against bacteria viz. Staphylococcus aureus, Escherichia coli and Candida albicans. The obtained results showed that the chitosan-chloroquinoline derivative might be a promising candidate for novel antimicrobial agents for biomedical applications.     

Preparation and anticoagulant activity of a fucosylated polysaccharide sulfate from a sea cucumber Acaudina molpadioidea

A fucosylated polysaccharide sulfate, AMP-2, was purified by DEAE-Sepharose Fast Flow and Sephadex G-100 columns in successive steps from a special sea cucumber in southeastern China. HPLC and cellulose acetate membrane electrophoresis experiments confirmed AMP-2 was a homogenous carbohydrate with a relative molecular weight of ca. 2.4 × 10⁴ Da, and methylation analysis indicated that polysaccharide was composed of 1-substituted-Galp, 1,4-disubstituted-GalNp, 1,2-disubstituted-FucSp, 1,4,6-trisubstituted-Glcp in a molar ratio of ca. 0.5:2.0:1.0:3.0, together with a small amount of different substituted Manp. Sulfated derivative and carboxymethylated derivative were prepared using dry pyridine and chlorosulfonic acid, and chloroacetic acid, respectively. Anticoagulant activities in vitro investigation showed that sulfated derivative showed a stronger ability than native polysaccharide and carboxymethylated derivative, which might be caused by their different percentages and types of functional groups in their structures.     

Riccardin C,a novel cyclic bibenzyl derivative from Reboulia hemisphaerica

Riccardin C, a novel cyclic bibenzyl derivative with a biphenyl ether and biphenyl linkages, and the previously known ent-aristolone have been isolated from the liverwort Reboulia hemisphaerica. Riccardin C trimethyl ether was identical to the dimethoxy derivative of riccardin A isolated from the liverwort Riccardia multifida.     

New germacranolides and other constituents from Trichogoniopsis morii

Trichogoniopsis morii afforded, in addition to known compounds, a new toxol derivative, two diterpenes, a labdane and an ent-kaurane derivative, an eudesmanolide and five germacranolides, a furanoheliangolide and four 1-oxo-germacranolides. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomy of the genus Trichogoniopsis is discussed briefly.     

A labdane derivative from Chromolaena collina and a p-hydroxyacetophenone derivative. From Stomatanthes corumbensis

A new labdane derivative, 7α-acetoxy-trans-communic acid was isolated from Chromolaena collina. Extraction of Stomatanthes corumbensis yielded a new p-hydroxyacetophenone derivative which was identified as 4-methoxy-3- [3′-methyl-4′-angeloyloxy-but-2-en- 1′-yl ]-acetophenone.     

3-O-methyl galactose found in polysaccharides of Lampteromyces japonicus

A polysaccharide fraction from Lampteromyces japonicus contained a sugar (4%), which was identified as 3-O-methyl galactose by demethylation with boron trichloride, periodate oxidation of the methyl glycoside derivative and gas chromatography-mass spectrometry of the alditol acetate derivative.     

Transformation of 3-(3-carboxyphenyl)alanine in iris species An example of diversity in catabolism of secondary plant products

3-(3-Carboxyphenyl)-DL-[2-¹⁴C]alanine has been incorporated into four species of iris. In all species extensive metabolization takes place. In Iris × hollandica, in which both the alanine derivative and 3′-carboxyphenylglycine occur, the products identified are the glycine derivative, 3′-carboxyphenylacetate acid, 3′-carboxymandelic acid, and 3′-carboxyphenylglyoxylic acid. In I. sanguinea, in which the alanine and glycine derivatives also occur, the products identified are the glycine and acetic acid derivatives but the major product is 3-(3-hydroxymethylphenyl)alanine, a naturally occurring amino acid in this species. In I. tectorum, in which only the carboxy-substituted alanine derivative occurs, the products identified are the acetic acid and glyoxylic acid derivatives. In I. pallida, not containing any of the meta-substituted amino acids, the products identified are again the acetic acid and glyoxylic acid derivatives. The results have been further substantiated by incorporation of labelled 3′-carboxyphenylacetic acid and 3′-carboxymandelic acid into I. × hollandica and I. sanguinea.The results demonstrate three different metabolic patterns for the alanine derivative and confirm previous results on the pathway from the alanine to the glycine derivative. Furthermore, the results may be of significance for the elucidation of the catabolism of phenylalanine.     

Eremophilane derivatives and other constituents from Senecio species

The investigation and reinvestigation respectively of 23 Senecio species afforded 11 further cacalol derivatives, a furoeremophilone, 17 eremophilanes, 4 bisabolene derivatives, a shikimic acid derivative, a bis-prenylated p-hydroxybenzaldehyde, menth-2-en- 1,7-diol and a cumol derivative. The configuration of some eremophilanes have been revised. Structures were elucidated by spectroscopic methods. The results are summarized in a table. The chemotaxonomic aspects agree with those of previous investigations.     

Synthesis and properties of a photoaffinity probe for the glucagon receptor in hepatocyte plasma membranes

The reaction of glucagon with 4-fluoro-3-nitrophenylazide has been shown to afford the photosensitive derivative, N^?-4-azido-2-nitrophenyl-glucagon. The structure and properties of this derivative were established by amino acid analysis, absorption and fluorescence spectroscopy, deamination, Edman degradation and photolysis. This photoaffinity derivative of glucagon has been used to label specifically glucagon binding sites on hepatocyte plasma membranes.     

Mass spectra of acetylated derivatives of sialic acids

The fragmentation pattern in electron-impact mass spectrometry has been established for the peracetylated methyl ester methyl glycoside derivative of N-acetylneuraminic acid. The resulting, data allow the interpretation of the mass spectrum of the corresponding derivative of a new sialic acid isolated from the starfish Distolasterias nipon which is shown to be 8-O-methyl-N-acetylneuraminic acid.     

Structure-Plant Phytotoxic Activity Relationship of 7,7′-epoxylignanes, (+)- and (−)-verrucosin: Simplification on the aromatic ring substituents

The synthesized 7-aryl derivatives of (7R,7′S,8S,8′S)-(+)-verrucosin were applied to growth inhibitory activity test against ryegrass at 1 mM. 7-(3-Ethoxy-4-hydroxyphenyl) derivative 12 and 7-(2-hydroxyphenyl) derivative 4 showed comparable activity to those of (+)-verrucosin against the root (−95%) and the shoot (−60%), respectively. The growth inhibitory activity test against lettuce using synthesized 7-aryl derivatives of (7S,7′R,8R,8′R)-(−)-verrucosin at 1 mM showed that the activities of 7-(3-hydroxyphenyl) derivative 20 and 7-(3-ethoxy-4-hydroxyphenyl) derivative 28 are similar to that of (−)-verrucosin against the root (−95%). Against the shoot, 7-(3-hydroxyphenyl) derivative 20 showed higher activity (−80%) than that of (−)-verrucosin (−60%). As the next step, (7S,7′R,8R,8′R)-7-(3-hydroxyphenyl)-7′-aryl-(−)-verrucosin derivatives, in which the most effective 3-hydroxyphenyl group is employed as 7-aromatic ring, were synthesized for the assay against lettuce. In this experiment, 7′-(2-hydroxyphenyl) derivative 37 and 7′-(3-hydroxyphenyl) derivative 38 showed similar activity to that of derivative 20. The effect of 7- and 7′-aryl structures of 7,7′-epoxylignanes on the plant growth inhibitory activity was clarified. The 7- and 7′-aryl structures were simplified to show comparable activity to or higher activity than that of (−)-verrucosin. The plant growth inhibitory activity of a nutmeg component, (+)-fragransin C_3b, was estimated as −80% inhibition at 1 mM against ryegrass roots.     

Sesquiterpenes,guaianolides and diterpenes from Stevia myriadenia

The investigation of Stevia myriadenia afforded in addition to known compounds a new clerodane and a labdane derivative, two guaianolides, a bisabolene and a germacrene derivative. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.     

Monomolar acetalations of methyl α-d-mannosides—synthesis of methyl α-d-talopyranoside

Methyl α-d-mannopyranoside (1 mole) reacts with 2,2-dimethoxypropane (1 mole), to give the 4,6-O-isopropylidene derivative (2) which rearranges to the 2,3-O-isopropylidene derivative (4). Compound4 can also be prepared by graded hydrolysis of methyl 2,3:4,6-di-O-isopropylidene-α-d-mannopyranoside. Successive benzoylation, oxidation, and reduction of4 provides a useful route to a number ofd-talopyranoside compounds. Methyl α-d-mannofuranoside (1 mole) reacts with 1–2 moles of 2,2-dimethoxypropane to give the 5,6-O-isopropylidene derivative (16) in 90% yield.     

Nα-Trinitrophenyl glucagon An inhibitor of glucagon-stimulated cyclic AMP production and its effects on glycogenolysis

N^α-Trinitrophenyl glucagon was prepared by reaction with trinitrobenzene sulfonic acid and purified by ion-exchange chromatography. This derivative has essentially no ability to activate adenylate cyclase from rat liver nor to increase the levels of cyclic AMP in isolated hepatocytes nor to stimulate protein kinase activity. This derivative also can act as a glucagon antagonist with regard to cyclic AMP production and can decrease the degree of stimulation of adenylate cyclase caused by glucagon, as well as lowering the glucagon-stimulated elevation of cyclic AMP levels in intact hepatocytes. Nevertheless, this derivative is capable of activating glycogenolysis.in isolated hepatocytes and in augmenting the effect of glucagon on glycogenolysis. This metabolic effect of the glucagon derivative thus appears to occur independent of changes in cyclic AMP levels. These results suggest that glucagon can also activate glycogenolysis by a cyclic AMP-independent process.     

The stepwise synthesis of an aldopentaouronic acid derivative related to branched (4-O-methylglucurono)xylans

Benzylation of methyl 2,3-anhydro-4-O-[2-O-benzyl-3,4-di-O-(β-D-xylop yranosyl]-β-D-xylopyranosyl]-β-D-ribopyranoside (1) afforded the crystalline. fully benzylated tetrasaccharide derivative 2. The octa-O-benzyl derivative 3, having only HO-2 unsubstituted, obtained by treatment of 2 with benzyl alcoholate anion in benzyl alcohol, was allowed to react in dichloromethane with methyl 2,3-di-O-benzyl- 1-chloro-1-deoxy-4-O-methy]-α,β-glucopyranuronate in the presence of silver perchlorate and triethylamine to give the branched, 4-O-methyl-α-D-glucuronic acid-containing pentasaccharide derivative 4a as the major product. Subsequent debenzylation afforded the aldopentaouronic acid derivative 5a, which contains all the basic structural features of branched, hardwood (4-O-methylglucurono)xylans. The structure of 5a was confirmed by analysis of its ¹³C-n.m.r. spectrum and the mass-spectral fragmentation pattern of the corresponding fully methylated derivative 6a.     

Synthesis and reactions of some hydrazones of dehydro-l-ascorbic acid

l-threo-2,3-Hexodiulosono-1,4-lactone 2-(3-chlorophenylhydrazone) and 4- (2-acetoxyethylidene)-4-hydroxy-2,3-dioxobutano-1,4-lactone 2-(3-chlorophenylhydrazone) were prepared. The two geometric isomers of the corresponding bis(hydrazone) underwent an intramolecular rearrangement to 1-(3-chlorophenyl)- 3-(l-threo-glycerol-1-yl)-4,5-pyrazoledione 4-(3-chlorophenylhydrazone), which gave a tri-O-acetyl derivative upon acetylation and the anticipated formyl derivative upon periodate oxidation. Oxidation of the bis(hydrazone) with cupric chloride afforded the bicyclic compound 3,6-anhydro-3-C-(3-chlorophenylazo)-l- xylo-2-hexulosono-1,4-lactone 2-(3-chlorophenylhydrazone), whose acetylation afforded the mono-O-acetyl derivative.     

The reaction of phosphorus pentachloride with amides,in particular 2-acetamido-2-deoxyaldohexopyranoses

2-acetamido-2-deoxyaldohexopyranose polyacetates are transformed by the action of phosphorus pentachloride into 2-tetrachloroethylideneamino derivatives, the trans-2-acetamido-l-acetate system reacting more rapidly than the cis. A 1-acetamido-pyranosyl polyacetate afforded the 1-tetrachloroethylideneamino derivative and 2-O-trichloroacetyl-β-D-glucopyranosyl chloride. The latter was also observed, amongst other products, from the reaction of β-D-glucopyranosyl azide tetra-acetate with phosphorus pentachloride. Similar reactions on acetamidocyclohexane and its 2-acetoxy derivative afforded dichloroacetamido, trichloroacetamido, and tetrachloroethylideneamino derivatives. Likewise, 1-acetamido-2-acetoxyethane gave the 1-dichloroacetamido derivative.     

Isolation of tuberospironine A,a novel croomine derivative from Stemona tuberosa Lour.

A novel croomine derivative, tuberospironine A (3-epi-tuberospironine) was isolated from the root extracts of Stemona tuberosa Lour. found growing on Seram Island, Moluccas Province, Indonesia. The structure of this novel alkaloid, with unprecedented configuration at C-3 for a croomine derivative, was determined from interpretation of its NMR spectroscopic data.