New syntheses and13C NMR spectra of the methyl ethers of methyl α-L-arabinopyranoside

A method is described for obtaining the methyl ethers of methyl -L-arabinopyranoside that is based on the partial methylation of methyl -L-arabinopyranoside followed by the liquid chromatography of the methyl ethers. The¹³C NMR spectra of the methyl ethers of methyl -L-arabinopyranoside have been studied.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 178–181, March–April, 1985.     

Synthesis of methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside

A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers.     

New syntheses of methyl ethers from methyl α-L-fucopyranoside

A method for obtaining methyl esters of methyl -L-fucopyranoside based on the partial methylation of methyl -L-fucopyranoside with the subsequent liquid and gasliquid chromatography of the methyl ethers is described. Their properties are given.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 309–312, May–June, 1985.     

Synthesis of methyl ethers of methyl (methyl α-D-mannopyranosid)-uronate

Methyl (methyl -D-mannopyranosid)uronate (I) has been obtained by the catalytic oxidation of methyl -D-mannopyranoside with oxygen in the presence of platinum carbon with a yield of 20%. The partial methylation of (I) and preparative column chromatography on silica gel has provided a convenient method of obtaining all the methyl ethers of (I) in the individual state.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 203–205, March–April, 1987.     

Synthesis of methyl ethers of methyl (methyl β-D-galactopyranosid)uronate

The oxidation of methyl -D-galactopyranoside with oxygen in the presence of platinum and carbon gave methyl (methyl -D-galactopyranosid)uronate (I) with a yield of 20%. The partial methylation of (I) with methyl iodide in the presence of silver oxide followed by preparative liquid chromatography on silica gel provided a convenient method for obtaining all the methyl ethers in the individual state.Pacific Ocean Institute of Bioorganic Chemistry. Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 37–39, January–February, 1987.     

Synthesis of methyl ethers of methyl (methyl α-D-glucopyranosid)uronate

Methyl (methyl -D-glucopyranosid)uronate (I) has been obtained by the catalytic oxidation of methyl -D-glucopyranoside with oxygen in the presence of platinum on carbon with a yield of 31%. The partial methylation of (I) followed by preparative liquid column chromatography on silica gel has provided a convenient method of obtaining all the methyl ethers of (I) in the individual state.Pacific Ocean Institute of Bioorganic Chemistry, Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 35–37, January–February, 1987.     

Syntheses of methyl α-dl-mycaminoside, methyl α-dl-oleandroside, methyl β-dl-cymaroside, methyl α-dl-tyveloside and methyl α-dl-chromoside C

Five rare hexoses, which are components of antibiotics or cardiac glycosides, have been synthesized as methyl glycosides through a common intermediate methyl 2,3-dehydro-2,3,6-trideoxy-α-dl glucopyranoside (7). Epoxidation and subsequent treatment with dimethylamine of7 afforded methyl α-dl-mycaminoside (9). The addition reaction of MeOH to12 gave methyl α-dl-oleandroside (15) and methyl β-dl-cymaroside (17). The hydroxymercuration and subsequent reduction of12 afforded methyl α-dl-chromoside C (19) and methyl β-dl-tyveloside (25).     

Micropreparative gas-liquid chromatography of the products of the partial methylation of methyl α-L-rhamnopyranoside

Summary A method has been developed for obtaining acetates of the methyl ethers of methyl -L-rhamnopyranoside by the preparative gas-liquid chromatography of the products of the partial methylation of methyl -L-rhamnopyranoside, and the properties of the compounds isolated have been described.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 142–144, March–April, 1979.     

Specific features of the interaction of methyl ethers of methyl (methyl-α-D-galactopyranoside)uronate with trimethylsilyl ions in the gas phase

Specific features of the interaction between trimethylsilyl ions and methyl (methyl-α-d-galactopyranoside)uronate and its methyl ethers were revealed. It was shown that a hydrogen atom is generated when the trimethylsilyl ion is located at hydroxyl group. This atom migrates over the methoxy and hydroxyl groups toward the glycoside methoxy group, resulting in the formation of [Me+SiMe₃−MeOH]⁺ ions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1317–1319, July, 1997.     

Partial methylation of methyl glycosides

Summary The partial methylation of methyl xylo-, arabino-, lyxo- and rhamnopyranosides by Purdie's method has been studied; it is possible to use the results obtained for the isolation of individual methyl ethers by micro-preparative GLC.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 682–686, November–December, 1975.     

Mass spectra of alkenyl methyl ethers

Electron impact ionization mass spectra of numerous alkenyl methyl ethers C_nH_2n-1OCH₃ (n = 3–6) recorded under normal (4 kV, 70 eV, 175°C) and low-energy, low-temperature (8 kV, 12 eV, 75 °C) conditions are reported. The influence of the position and stereochemistry of the double bond on the dissociation of ionized alkenyl methyl ethers is discussed. The mechanisms by which these ethers fragment after ionization have been further investigated using extensive ²H-labelling experiments and by studying the energy dependence of the reactions. Ethers of allylic alcohols show spectra that are distinct from those of the isomeric species in which the double bond is separated by one or more sp³ carbon atoms from the carbon atom carrying the methoxy group. Three principal primary fragmentations are observed. The most common process, especially for ionized ethers of allylic alcohols, is loss of an alkyl group. This reaction often occurs by simple α-cleavage of radical-cations of the appropriate structure; however, alkyl groups attached to either end of the double bond are also readily lost. These formal β- and γ-cleavages are explained in terms of rearrangements via distonic ions and, at least in the case of γ-cleavages, ionized methoxycyclopropanes. Ionized homoallyl methyl ethers tend to eliminate an allylic radical, particularly at high internal energies, with formation of an oxonium ion (CH₃ ⁺O?CH₂ or CH₃ ⁺O?CHCH₃). The ethers of linear pentenols and hexenols show abundant [M - CH₃OH]⁺? ions in their spectra, especially when a terminal methoxy group is present Methanol loss also takes place from ionized ethers of allylic alcohols in which there is a Δ-hydrogen atom; this process is significantly favoured by cis, rather than trans, stereochemistry of the double bond.     

Synthesis of methyl derivatives of uronic acids. I. Synthesis of methyl (methylα-D-galactopyranosid)uronate and its 2-, 3-, and 4-O-methyl ethers

Alternative unidirectional methods for synthesizing methyl (methyl α-D-galactopyranosid)uronate and its mono-O-methyl ethers by the oxidation (with CrO₃-H₂SO₄-acetone) of the corresponding methyl O-benzyl-O-methyl-α-D-galactopyranosides having unsubstituted 6-OH groups to the corresponding methyl O-benzyl-O-methyl-α-D-galactouronic acids followed by esterification with CH₂N₂ and the catalytic hydrogenolysis of the benzyl groups are proposed.     

Synthesis of methyl derivatives of uronic acids II. Synthesis of the 2,3-, 2,4-, and 2,4-di- and 2,3,4-tri-O-methyl ethers of methyl (methylα-D-galactopyranosid) uronate

Unidirectional methods are proposed for the synthesis of the 2,3-, 2,4-, and 3,4-di-, and 2,3,4-tri-O-methyl ethers of methyl (methyl α-D-galactopyranosid) uronate by the oxidation (CrO₃-H₂SO₄-acetone) of the corresponding methyl O-benzyl-O-methyl-α-D-galactopyranosides having unsubstituted 6-OH groups to the corresponding (methyl O-benzyl-O-methyl-α-D-galactosid) uronic acids followed by esterification with CH₂N₂ and catalytic hydrogenolysis of the benzyl groups.     

A total synthesis of the methyl glycoside of ganglioside GM(1)

The total synthesis of the methyl glycoside of GM(1) (1b) has been accomplished. The key step in the synthesis involves the sulfonamidoglycosidation reaction, which is used to create a beta-linkage leading to a GalNAc residue joined to the C4 hydroxyl group of a galactose unit of a C3 sialylated lactosyl moiety. The "proximal hydroxyl" directing effect, which has been postulated before, manifests in this context as well leading to the preponderant formation of the beta-glycoside. Together with asialo GM(1) and other substructures, the GM(1) methyl glycoside has been submitted for biological assays as potential ligands for bacterial and viral infection sites.     

An effective synthesis of α-glycosides of -acetylneuraminic acid derivatives by use of 2-deoxy-2β-halo-3β-hydroxy-4,7,8,9-tetra- -acetyl- -acetylneuraminic acid methyl ester

Condensation of a new glycosyl donor, methyl 5-acetamido-4, 7,8,9-tetra- -acetyl-2,3-dibromo-2,3,5-trideoxy-β- -2-nonulopyranosonate with various acceptors such as methyl 2,3,4-tri- -benzyl-α- -glucopyranoside, cholesterol, methyl 2,4,6-tri- -bonzyl-α- -galactopyranoside, and nethyl 5-acetamido-4,7,9-tri- -acetyl-2,6-anhydro-3,5-dideoxy- -non-2-enopyranosonate gave only the corresponding β-glycosides. The 3α-bromo group of the glycoaides obtained above was reduced with tributylstannane to the corresponding glycosids, which were deprotected to give the free glycoaides in high yields.     

Elimination of β-palladium hydroxide in the Pd-catalyzed reaction of methyl (α-hydroxymethyl)acrylate with alcohols

Exclusive elimination of β-Pd-OH takes place in the oxypalladation intermediate derived from methyl (α-hydroxymethyl)acrylate and alcohols with PdCl₂ catalyst, and no β-Pd-H elimination occurs.     

Structure of Yononin A novel type of spirostanol glycoside

Two isomeric monomethyl ethers of yonogenin (25 ,5β-spirostane-2β,3-diol) have been synthesized and the 3-methyl ether identified as the aglycone of permethyl yononin. Thus, yononin, an - -arabinoside of yonogenin from the rhizome of Dioscorea Tokoro Makino, is shown to be a novel type of spirostanol glycoside in which the sugar moiety is attached to the hydroxyl group at C-2, and not at C-3, of the aglycone.     

Ozonolysis of olefins,V: Emulsion ozonization of methyl linoleate and methyl linolenate in aqueous alkaline hydrogen peroxide

Summary The ozonolysis of methyl linoleate and methyl linolenate in neutral and alkaline aqueous emulsions of hydrogen peroxide was investigated. Besides the expected products such as dimethyl malonate (3b), dimethyl azelate (3h) and methyl hexanoate (2a) further homologous methyl esters of dicarboxylic acids (3a–g), oxo carboxylic acids (4a, b, e–h) and hydroxy carboxylic acids (4c, d) could be detected by GC/MS analysis. Furthermore a method for separation of 8-hydroxyoctanoic acid (4d) by methylation and extraction of the reaction mixture containing the ozonolysis products is described.

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Ozonolyse von Olefinen, V: Ozonolyse von Linol-und Linolensäuremethylester in wäßriger alkalischer Emulsion von Wasserstoffperoxid

Zusammenfassung Die Ozonolyse von Linol- und Linolensäuremethylester wurde in neutraler bzw. alkalischer wäßriger Emulsion von Wasserstoffperoxid untersucht. Dabei wurden im Reaktionsgemisch mittels GC/MS neben Malonsäuredimethylester (3b), Azelainsäuredimethylester (3h) und Hexansäuremethylester (2a) weitere homologe Dicarbonsäuren (3a–g), Oxocarbonsäuren (4a, b, e–h) und Hydroxycarbonsäuren (4c, d) nachgewiesen. Weiters wurde eine Methode ausgearbeitet, mit der es gelang, 8-Hydroxyoctansäure (4d) — eine hinsichtlich ihrer biologischen Aktivität bedeutende Verbindung — durch Methylierung und Extraktion aus dem Reaktionsgemisch abzutrennen.

     

Michael additions to acrylonitrile,methyl acrylate and methyl vinyl ketone to Nb-benzylidenetryptophan methyl ester

Michael addition to methyl acrylate and methyl vinyl ketone of N_b-benzylidene-L-tryptophan methyl ester 1 gave 2-(3-indolylmethyl)glutamic dimethyl ester 2a and α-(3-oxobutyl)tryptophan methyl ester 2b respectively. Addition to acrylonitrile of 1 yielded α,N_a-dicyanoethyltryptophan methyl ester 3 .