M. A. M. Nassr

Mercuricyclisation in carbohydrate chemistry: a highly stereoselective route to α-D-C-glucopyranosyl derivatives

Mercuricyclisation of an olefin which is prepared from the carbohydrate 2,3,4,6-tetra-O-benzyl-D-glucopyranose using a Witting reaction provides the axial chloromercuri-ether as the only isolated product, thus offering the first stereospecific route to 1,5-trans-(e.g. α-D)C-glucopyranosyl derivatives.

Heterocycles from saccharide hydrazones : Part I. Saccharide 1,3,4-oxadiazoles

Abstract Oxidation, with iodine-mercuric oxide, of acetylated saccharide aroylhydrazones and of aromatic aldehyde hydrazones yields 5-aryl-2-(polyacetoxyalkyl)-1,3,4-oxadiazoles and 2,5-diaryl-1,3,4-oxadiazoles, respectively. On de- O -acetylation, saccharide oxadiazole acetates rearrange to the tautomeric, cyclic iminolactones which, on reacetylation, regenerate the starting oxadiazoles. Attempted dehydration of saccharide acetyl- and benzoyl-hydrazones by treatment with boiling acetic anhydride under reflux resulted in the formation of peracetylated N,N -diacetylhydrazones and- N -acetyl- N -benzoylhydrazones, respectively.

Selective cyclisation of 2,3,4,5-tetra-O-acetylgalactaric acid bis[alkylthio(thiocarbonyl)]hydrazides to saccharide 1,3,4-oxadiazole, thiadiazole, and thiadiazoline derivatives

The syntheses of galactaric acid acetate bis[alkylthio-(thiocarbonyl)]hydrazides (1,2) are described. Selective cyclisation of both hydrazide 1 and 2 was investigated. Using phosphorous oxychloride as a cyclising agent, loss of water produced 1,2,3,4-tetra-O-acetyl-1,4-bis(5-S-methyl or benzyl)-1,3,4-thiadiazol-2-yl)galacto-tetritol (3) or (4). Use of thionyl chloride lead to dehydrosulfurization and gave 1,2,3,4-tetra-O-acetyl-1,4-bis(5-S-methyl or benzyl)-1,3,4-oxadiazol-2-yl)galacto-tetritol (5) or (6). Finally, with triethyl orthoformate as the cyclising agent, compound 1 or 2 gave 3,3′-(2,3,4,5-tetra-O-acetylgalactar-1,6-dioyl)-bis-[(2-ethoxy-2,3-dihydro-5-S-methyl or benzyl)-1,3,4-thia-diazole] (7) or (8).

Cyclization of aldonic acid aroylhydrazides to 1,3,4-oxadiazoline derivatives

Abstract d -Glucono-1,5-lactone reacts with aroylhydrazines to give the corresponding 1-aroyl-2- d -gluconylhydrazines. Condensative cyclization of these compounds using triethyl orthoformate gave the corresponding 5-aryl-2-ethoxy-3- d -gluconyl-2,3-dihydro-1,3,4-oxadiazoles.

Cyclization of 2,3,4,5-tetra-O-acetylgalactaric bis-(aroylhydrazides) to saccharide bis(1,3,4-oxadiazolyl) derivatives

Abstract Condensation of 2,3,4,5-tetra-O-acetylgalactaroyl dichloride with two equivalents of various aroylhydrazines gave the corresponding 2,3,4,5-tetra-O-acetylgalactaric bis(aroylhydrazides). Condensative and dehydrative cyclization of these bis(hydrazides) with triethyl orthoformate and phosphoryl chloride, respectively, gave the corresponding 3,3′-(2,3,4,5-tetra-O-acetylgalactar-1,6-dioyl)-bis(5-aryl-2-ethoxy-2,3-dihydro-1,3,4-oxadiazole) and 1,2,3,4-tetra-O-acetyl-1,4-bis(5-aryl-1,3,4-oxadiazol-2-yl)-galacto-tetritols. The elucidation of the structure of the compounds prepared is discussed and mechanistic pathways for their formation are proposed.

(2-Quinoxalinon-3-YL)glyoxal derivatives from L-ascorbic acid☆

Abstract Reaction of dehydro- L -ascorbic acid with o -phenylenediamine, followed by aroylhydrazines, gave 3-[1-(aroylhydrazono)- L - threo -2,3,4-trihydroxybutyl]-2-quinoxalinones which, upon periodate oxidation, gave 3-[1-(aroylhydrazono)glyoxal-1-yl]-2-quinoxalinones. Various derivatives having substituents on the phenyl ring were also prepared. Reaction of 3-[1-(benzoylhydrazono)glyoxal-1-yl]-2-quinoxalinone with benzoylhydrazine gave 3-[1,2-bis(benzoylhydrazono)glyoxal-1-yl]-2-quinoxalinone, and its reduction gave 3-[1-(benzoylhydrazono)-2-hydroxyethyl]-2-quinoxalinone.

Syntheses of 2-acetamido-2-deoxy-4-O-α-D-glucopyranosyl-α-d-glucopyranose (n-acetylmaltosamine) and 2-acetamido-2-deoxy-4-O-β-d-glucopyranosyl-α-d-glucopyranose

Abstract Condensation of benzyl 2-acetamido-3,6-di- O -benzyl-2-deoxy-α- D -glucopyranoside with 2,3,4,6-tetra- O -benzyl-1- O -( N -methyl)acetimidoyl-β- D -glucopyranose gave benzyl 2-acetamido-3,6-di- O -benzyl-2-deoxy-4- O -(2,3,4,6-tetra- O -benzyl-α- D -glucopyranosyl)-α- D -glucopyranoside which was catalytically hydrogenolysed to crystalline 2-acetamido-2-deoxy-4- O -α- D -glucopyranosyl-α- D -glucopyranose ( N -acetylmaltosamine). In an alternative route, the aforementioned imidate was condensed with 2-acetamido-3- O -acetyl-1,6-anhydro-2-deoxy-β- D -glucopyranose, and the resulting disaccharide was catalytically hydrogenolysed, acetylated, and acetolysed to give 2-acetamido-1,3,6-tri- O -acetyl-2-deoxy-4- O -(2,3,4,6-tetra- O -acetyl-α- D -glucopyranosyl)-α- D -glucopyranose Deacetylation gave N -acetylmaltosamine. The synthesis of 2-acetamido-2-deoxy-4- O -β- D -glucopyranosyl-α- D -glucopyranose involved condensation of benzyl 2-acetamido-3,6-di- O -benzyl-2-deoxy-α- D -glucopyranoside with 2,3,4,6-tetra- O -acetyl-α- D -glucopyranosyl bromide in the presence of mercuric bromide, followed by deacetylation and catalytic hydrogenolysis of the condensation product.

Studies on the products obtained by the periodate oxidation of osazones. II

Abstract The n.m.r. spectra of mesoxalaldehyde 1,2-bis(phenylhydrazone) and tris(phenylhydrazone) suggest chelations as in structures 1 and 2 . Acid reagents convert these two compounds into I -phenyl-4-phenylazopyrazole ( 4 ). A number of substituted 4 were prepared from the corresponding 1 . The conversion of saccharide phenylosazones into I -phenyl-4-phenylazo-2-pyrazolin-5-one ( 5 ) probably proceeds through the formation of a 3,6-anhydro ring.

New Synthesis of Monomeric and Polymeric Saccharide bis-Hydrazide Diamines Salts. Reaction of 2, 3, 4, 5-Tetra-O-acetyl Galactaric Acid bis-Hydrazides with Different Diamines

Abstract Reaction of 1-(2,3,4,5-tetra-o-acetylgalactaroy1)bis-2-[thiomethyl or thiobenzy1(thiocarbony1)]hydrazine 1 or 2 with different bifunctional amines [piperazine (PPZ), tetraethyl-ethylenediamine (TEED), tetramethylethylenediamine (TMED), and tetramethyl propanediamine (TMPD)] at different hydrazide/diamine ratios in methanol, gave the corresponding monomeric and polymeric bis-hydrazide salts. Elucidation of the structures of compounds prepared are discussed and mechanistic pathways for their formation are proposed.

Oxidation of mesoxalaldehyde bis- and tris-(benzoylhydrazones)

Mesoxalaldehyde bis(benzoylhydrazone) was oxidised with iodine and mercuric oxide to 2,2′-bis-(5-phenyl-1,3,4-oxadiazolyl). Mesoxalaldehyde tris(benzoylhydrazone) gave, on similar oxidation, 1-α-benzoyloxybenzylideneamino-1,2,3-triazole-5-carbaldehyde benzolyhydrazone. Saccharide 1-α-benzoyloxybenzylideneamino-1,2,3-triazoles obtained from saccharide bis(benzoylhydrazones) gave on hydrolysis and periodate oxidation 1-benzoylamino-1,2,3-triazole-4-carbaldehyde. The different course in these reactions was attributed to different modes of chelation.