Kiyoshi Takiura

Stereochemistry of the methoxymercuration of glycal acetates

Abstract The methoxymercuration of the acetates of d -glucal, d -galactal, l -arabinal and d -xylal was studied by n.m.r. spectroscopy, and by stereoselective demercuration with thiourea, as well as by reductive demercuration with sodium borohydride. It is considered to be a trans -addition to the double bond to yield isomeric methyl glycosides having mercury attatched to C-2. The proportion of diaxial to diequatorial addition is strongly affected by the protecting groups at C-4 and C-5.

Fluorometric determination of adenine and its derivatives by reaction with glyoxal hydrate trimer

Abstract A fluorometric determination of adenine has been devised. It was found that adenine gives strong fluorescence when reacting with glyoxal hydrate trimer in an acidic medium. The maximum wavelengths of excitation and emission spectra were 328 and 382 mμ, respectively. This reaction was successfully applied to determination of 0.2–1.0 or 2.0–10.0 mμmoles of adenine and its derivatives, in which the hydrogen atom at position 9 is substituted with ribose or substituted ribose. Other nucleic acid bases, guanine, uracil, thymine, and cytosine, did not interfere with this fluorometric determination of adenine.

Equimolar oxymercuration of D-glucal triacetate with mercuric perchlorate and its application to the synthesis of 2′-deoxy disaccharides

Abstract A search for appropriate reaction conditions for the equimolar methoxymercuration of D -glucal triacetate was made by using various mercuric salts, bases, and reaction solvents. Under optimum conditions with mercuric perchlorate, sym -collidine, and acetonitrile, D -glucal triacetate underwent methoxymercuration with an equimolar amount of methanol to afford methyl 3,4,6-tri- O -acetyl-2-deoxy-2-perchloratomercuri-β- D -glucopyranoside ( 1 , 26%) and its α- D - manno isomer ( 2 , 49%). Equimolar oxymercuration of D -glucal triacetate with partially protected sugars, followed by subsequent demercuration of the products with sodium borohydride, afforded α- and β-linked 2′-deoxy disaccharide derivatives in moderate yields. The partially protected sugars used were 1,2,3,4-tetra- O -acetyl-β- D -glucopyranose and 1,2:3,4-di- O -isopropylidene-α- D -galactopyranose, and the corresponding products were O -(3,4,6-tri- O -acetyl-2-deoxy-α- D - arabino -hexopyranosyl)-(1→6)-1,2,3,4-tetra- O -acetyl- D -glucopyranose( 4 , 23%) and its β-linked isomer ( 5 , 11%) from the former, and O -(3,4,6-tri- O -acetyl-2-deoxy-α- D - arabino -hexapyranosyl)-(1→6)-1,2:3,4-di- O -isopropylidene-α- D -galactopyranose ( 9 , 29%) and its β-linked isomer ( 10 , 10%) from the latter. Deacetylation of these 2′-deoxy disaccharides was effected with methanolic sodium methoxide, but deacetonation was unsuccessful owing to simultaneous cleavage of the glycosidic linkage.

Hydroxy- and acetoxy-mercuration of D-glucal triacetate

Abstract Hydroxy- and acetoxy-mercuration of D -glucal triacetate ( 1 ) afforded 2-acetoxymercuri-3,4,6-tri- O -acetyl-2-deoxy- D -glucose ( 2 ) and 2-acetoxymercuri-1,3,4,6-tetra- O -acetyl-2-deoxy-α- D -glucopyranose ( 3 ), respectively. On demercuration with sodium borohydride, compound 2 gave at first the acyclic 4,6-di- O -acetyl- D - erythro -hex-2-enose ( 4 ), which was further reduced to the corresponding hex-2-enitol derivative ( 5 ). Demercuration of 3 with borohydride gave a mixture of 1 and 1,3,4,6-tetra- O -acetyl-2-deoxy-α- D - arabino -hexopyranose ( 6 ). On the other hand, demercuration of 2 and 3 with thiourea yielded 4 and 1 , respectively. The reaction mechanisms of both oxymercurations are also discussed.

Periodate oxidation analysis of carbohydrates: Part IV. Simultaneous determination of aldehydes in di-aldehyde fragments as 2,4-dinitrophenylhydrazones by thin-layer or liquid chromatography

Abstract A method for the simultaneous determination of aldehydes in dialdehyde fragments, obtained from carbohydrate samples by periodate oxidation, is proposed. Reaction mixtures obtained from the periodate oxidation of carbohydrate samples are deionized by resins, and evaporated to dryness. The syrupy residues are treated with 2,4-dinitrophenylhydrazine hydrochloride in 1.2-dimethoxyethane at 25°C for 3 h. The resultant mixtures of hydrazones are separated by t.l.c. or l.c., and individual hydrazones are determined by spectrophotometric measurement. Reliable analyses of carbohydrate linkages are possible with 50–250-μg samples.

Studies of oligosaccharide linkages by simultaneous determination of component aldehydes in dialdehyde fragments as (2,4-dinitrophenyl)hydrazones

Abstract The component aldehydes in dialdehyde fragments formed by periodate oxidation of oligosaccharides were converted quantitatively into the corresponding (2,4-dinitrophenyl)hydrazones by the simple procedure of treatment with excess (2,4-dinitrophenyl)hydrazine hydrochloride in 1,2-dimethoxyethane. Then, by chromatographic separation of the hydrazones on a small column of silica gel and subsequent spectrophotometric analysis, it was possible to determine the position of glycosidic substitution in μmolar amounts of various types of glucobioses, oligosaccharides of senega, and some synthetic (1→6)-β- D -gluco-oligosaccharides.

Selective micro determination of unconjugated uronic acids by fluorescence reactions with ethylenediamine sulfate

Abstract A simple method for the spectrofluorimetric determination of uronic acids is proposed. The fluorescence at 328 (excitation) and 405 nm (emission) formed by heating sample solutions in acetate buffer containing large amounts of ethylenediamine sulfate, can be used to determine 1.0·10 -2 –3.0·10 -2 or 4.0·10 -2 –4.0·10 -1 μmole of unconjugated uronic acids accurately, without interference from other carbohydrate materials, especially uronides.

Periodate oxidation analysis of carbohydrates : Part I. Spectrophotometr1c determination of glyoxal in dialdehyde fragments formed from glycosides with 2,4-dinitrophenylhydrazine

Abstract A simple procedure for the determination of glyoxal in dialdehyde fragments, formed from glycosides by periodate oxidation, is proposed. By heating sample solutions prepared by dilution of reaction mixtures for periodate oxidation, with an aqueous dimethylsulfoxide solution of 2,4-dinitrophenylhydrazine hydrochloride. followed by addition of an aqueous ethanolic solution of potassium hydroxide, intense color with an absorption maximum at 576 nm developed. The spectrophotoinetric method based on this color reaction makes it possible to determine selectively 1·10 −2 –2·10 −1 μmole amounts of conjugated glyoxal without a prior liberation process. Data for glyoxal content obtained by this procedure are discussed in relation to overoxidation.

Iodinolysis of C-2 mercurated hexose derivatives

Abstract Reaction of the C-2 mercurated methyl hexopyranoside acetates 1–3 with an excess of iodine resulted in nearly quantitative replacement of mercury by iodine with retention and inversion of configuration at C-2. Similar replacement was observed with 2-acetoxymercuri-3,4,6-tri- O -acetyl-2-deoxy-α- d -glucopyranose ( 4 ). In the iodinolysis of 2-acetoxymercuri-1,3,4,6-tetra- O -acetyl-2-deoxy-α- d -glucopyranose ( 5 ) in methanol, however, replacement at C-2 was accompanied to a considerable extent by solvolysis of the 1-acetoxyl group, and a mixture of 1,2- trans isomers of methyl 3,4,6-tri- O -acetyl-2-deoxy-2-iodo-hexopyranosides having the d - gluco and d - manno configurations was obtained, together with 1,3,4,6-tetra- O -acetyl-2-deoxy-2-iodo-α- d -mannopyranose.

Selective colorimetric determination of p-haloaniline in a mixture with o -haloaniline by the reaction with chloranil

Summaryp-Haloanilines react with chloranil to develope an intense color (λmax: 545 nm), whileo-haloanilines do not. This difference in reaction has been applied to the selective determination ofp-haloanilines in a mixture witho-haloaniline.Zusammenfassungp-Halogenaniline geben mit Chloranil eine intensive Farbreaktion (λmax= =545 nm), während die entsprechenden o-Verbindungen dies nicht tun. Auf dieser Grundlage wurde eine selektive Bestimmungsmethode für p-halogenierte Aniline in Gemischen mit o-halogenierten Anilinen ausgearbeitet.