Periodate oxidation analysis of carbohydrates: Part IX. Evaluation of the use of pyridine as reaction solvent for oxidation of water-insoluble carbohydrate materials

Oxidation of methyl glycopyranosides with periodic acid in pyridine was studied by analysis of the reaction products by the dithioacetal method. Both C₂—C₃ and C₃—C₄ bonds were cleaved yielding three types of dialdehydes;secondary attack of these dialdehydes by periodic acid did not occur. Oxidation in aqueous pyridine proceeded in normal Malapradian fashion, but more slowly than for oxidation in water. Molar proportions of aldehydes were theoretical, when methyl glycosides were oxidized with periodic acid in a 1:1 ($\text{v}\text{v}$) mixture of pyridine and water. The structures of carbohydrate moieties in a few saponins and glycolipids were confirmed by analysis of the oxidation products obtained under similar conditions.     

Synthesis with an immobilized enzyme of N-acetyl-9-O-acetyl-neuraminic acid,a sugar reported as a component of embryonic and tumor antigens.

Condensation of 2-acetamido-6-$\text{O}$-acetyl-2-deoxy-D-mannose with pyruvic acid in the presence of immobilized acylneuraminate pyruvate lyase (2.8 units) gave 5-acetamido-9-$\text{O}$-acetyl-3,5-dideoxy-D-$\text{glycero}$-D-$\text{galacto}$-2-nonulopyranos-1-onic acid ($\text{N}$-acetyl-9-$\text{O}$-acetylneuraminic acid) on the 0.3 mmole scale.     

13C-NMR spectra of 6-aminohexyl glycosides of O-β-D-galactopyranosyl-2-acetamido-2-deoxy-β-D-glucopyranose

¹³C-NMR spectral data on 6-aminohexyl glycosides of $\text{O}$-β-$\text{D}$-galactopyranosyl-2-acetamido-2-deoxy-β-$\text{D}$-glucopyranose are pr     

The absolute configuration of berberastine and thalidastine

Optical resolution of (±)-tetrahydrojatrorrhizine using (-)-O,O-di-$\text{p}$-toluoyl-$\text{d}$-tartaric acid gave rise to (+)-tetrahydrojatrorrhizine ($\text{6}$ of high optical purity and of known absolute configuration. Oxidation of this enantiomer with lead tetraacetate, followed by acid hydrolysis, furnished alcohols $\text{10}$ and $\text{11}$ in a 2:1 ratio, whose relative stereochemistry was established from their nmr spectra. Iodine oxidation of the major alcohol $\text{10}$ led to protoberberinium salt $\text{14}$ which was found to be dextrorotatory. Since berberastine ($\text{1}$) and thalidastine ($\text{2}$) are also dextrorotatory, they must possess the same absolute configuration as $\text{14}$.     

Synthesis of a chito-tetrasaccharide β-1,4-GlcNAc-β-1,4-GlcN repeating unit

Abstract  

tert-Butyldimethylsilyl (4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl)-(1 → 4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranoside (Kawada and Yoneda [MOCHEM-D-09-00120], 2009), designed as a repeating disaccharide unit in a β-glucan having two different faces, was converted into a glycosyl donor and an acceptor. The glycosyl acceptor was glycosylated with the donor to afford a chito-tetrasaccharide derivative in good yield. Phthalimido and azido groups in the tetrasaccharide were successively converted into acetamido and free amino groups, and all other protecting groups were cleaved to obtain the chito-tetrasaccharide (2-amino-2-deoxy-β-d-glucopyranosyl)-(1 → 4)-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1 → 4)-(2-amino-2-deoxy-β-d-glucopyranosyl)-(1 → 4)-2-acetamido-2-deoxy-d-glucopyranose.     

Novel nucleoside analogues via direct attack of carbon : Nucleophiles on nucleosides containing epoxy-sugars

Direct ring-opening of the epoxide ring in 1-(5′-$\text{O}$-trityl-2′,3′-anhydro-β-D-lyxo-furanosyl) uracil (1) by lithium acetylide or vinylmagnesium bromide/cuprous iodide affords the corresponding 5′-$\text{O}$-trity]-3′-$\text{C}$-substituted-3′-deoxy-$\text{ara}$-uridine species.     

On the steric course of the addition of diallylzinc onto α,β-dialkoxy chiral carbonyl compounds: stereospecific synthesis of 2,6-dideoxysugars of the L-series

The synthesis of the 2,6-dideoxy sugars $\text{L}$-digitoxose (14), 2-deoxy-$\text{L}$-fucose (15) and $\text{L}$-mycarose (16) from the C₄ and C₅ chiral synthons (1), (2) and (3), through the intermediacy of the C₇ adducts (4), (8) and (12), obtained by $\text{erythro}$ addition of diallylzinc onto (1), (2) and (3), is reported.     

Core binding energies of the gaseous elements: the 3d levels of Te2 from X-ray photoelectron spectroscopy

The 3d levels of gaseous Te₂ have been studied by X-ray photoelectron spectroscopy. The binding energies are 580.14 ± 0.10 for the 3d_{$\text{5}\text{2}$} level and 590.45 ≈ 0.10 eV for 3d_{$\text{3}\text{2}$}. Comparison is made with the atomic binding energies of 581.33 (3d_{$\text{5}\text{2}$}) and 591.64 eV (3d_{$\text{3}\text{2}$}), computed using Desclaux's Dirac-Fock program, and with binding energies in ihe solid. The latter are ≈ 2.2 eV lower than those in Te₂.     

Cyanosugars III : The reaction of trimethylsilyl cyanide with keto,epoxy and acetal derivatives of carbohydrates

Reaction of methyl 2-acetamido-4,6-$\text{O}$-benzylidene-2-deoxy-α-$\text{D}$-$\text{ribo}$-hexopyranosid-3-ulose with Me₃SiCN afforded methyl 2-acetamido-4,6-$\text{O}$-benzylidene-3-$\text{C}$-cyano-2-deoxy-3-$\text{O}$-trimethylsilyl-α-$\text{D}$-$\text{allo}$- Reaction of ethyl 4,6-di-$\text{O}$-acetyl-2,3-anhydro-α-$\text{D}$-mannopyranoside with Me₃SiCN gave the corresponding ethyl 4,6-di-$\text{O}$-acetyl-2-$\text{C}$-cyano-2-deoxy-α-$\text{D}$-glucopyranoside. Reaction of methyl 4,6-$\text{O}$-benzylidene-2,3-anhydro-α-$\text{D}$-allopyranoside or methyl 4,6-$\text{O}$-benzylidene-2,3-di-$\text{O}$-tosyl-α-$\text{D}$-glucopyranoside with Me₃SiCN at - 75° or - 50° gave the corresponding methyl 6-$\text{O}$-[(R)-cyano phenyl methyl]-α-$\text{D}$-glyco-pyranosides with high or total regio and stereoselectivity.     

Stereochemical studies — 79 synthesis and kinetic study on the retrodiene decomposition of norbornene-condensed 1,3-oxazin-4-ones

The $\text{cis}$-$\text{cxo}$- amino acid $\text{c}$ with norbornene skeleton was converted into 2-aryvl-$\text{cis}$-$\text{cxo}$-1,3-oxazin-4-ones $\text{5a}$-$\text{d}$. These compounds, similarly to the $\text{diendo}$ isomers $\text{1a}$-$\text{d}$ studied by us earlier, undergo retrodiene decomposition under mild conditions to give 2-aryl-6$\text{2}$-l,3-oxazin-6-ones ($\text{2}$$\text{a}$-$\text{d}$) in 50-60% yield. The ratio of the decomposition rate constants of the tricyclic $\text{diendo}$ and $\text{diexo}$-1,3-oxazin-4-ones, measured in toluene solution, is about 2.     

Facile syntheses of 2,4,6-cycloheptatrienyl ketones

The synthesis of the 2,4,6-cycloheptatrienyl ketones $\text{1a}$–$\text{1e}$ by two alternative routes is reported: Route 1): The adducts $\text{3a–c}$ from the phenyl(trimethylsiloxy)-acetonitriles $\text{2a–c}$, known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones $\text{1a}$–$\text{1c}$. Route 2): the phenyl, methyl, and cyclopropyl ketone ($\text{1a}$, $\text{1d}$, $\text{1e}$) are prepared by treatment of the acid chloride $\text{7}$ with the corresponding organomanganese iodides RMnI ($\text{8a}$, $\text{8d}$, $\text{8e}$). The Fe-catalyzed coupling reaction of the acid chloride $\text{7}$ with a Grignard reagent was also used for the preparation of ketone $\text{1b}$.     

Selection of protecting groups and synthesis of a β-1,4-GlcNAc-β-1,4-GlcN unit

Abstract  

The synthesis of the disaccharide tert-butyldimethylsilyl (4-O-acetyl-2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-β-d-glucopyranoside, designed as a repeating unit appearing in oligo- and polysaccharides, which exhibits a distinguished “obverse–reverse” property in β-1,4-glucan chain, was accomplished. This disaccharide was synthesized by glycosylation of a phthalimido sugar with an azido sugar. A selective removal of the two different protecting groups at C-2 for obtaining 2-acetamido-4-O-(2-amino-2-deoxy-β-d-glucopyranosyl)-2-deoxy-β-d-glucopyranose indicates that the selection and combination, using phthalimido and azido as protecting groups, are an excellent strategy for synthesizing such target disaccharides.     

The isothermal Joule-Thomson coefficient of acetone and of chloroform

Using a flow calorimetric apparatus, measurements of the isothermal Joule-Thomson coefficient of acetone and chloroform have been made over the range 313.15 to 373.15 K. Values of ($\text{B-}\text{T}\text{d}\text{B}\text{d}\text{T}$) obtained from the measurements are found to be consistent with measurements of the second virial coefficient B. For acetone the measurements are also found to be consistent with values of $\text{T}{}^2\text{d}{}^2\text{B}\text{d}\text{T}{}^2$ obtained from the pressure derivative of the heat capacity. Best-fit equations are given, and parameters for the Stockmayer potential are found.     

Stereochemical studies 87saturated heterdcycles 82: Synthesis and steric structure of steredisomeric n-substituted tetrahydro-1,3-oxazines fused with norbornane or norbornene

$\text{diendo}$- and $\text{diexo}$-2-Methylamino and 2-benzylamino-3-hydroxymethylbicyclo [2.2.1]heptanes and the corresponding bicycio [2.2.1] heptenes ($\text{5a}$ -$\text{d}$, $\text{7a}$ -$\text{d}$) were synthesized from β-amino acid esters containing the norbornane or norbornene skeleton ($\text{3a}$-$\text{d}$). The aminoalcohols were converted to 5,8- methano -3,1-benzoxazines by reaction with formaldehyde. As established by ¹H and ¹³C NMR spectroscopy, the predominant conformation is $\text{endo - boat}$ ($\text{B}$) for the $\text{diexo}$, and $\text{exo - boat}$ ($\text{E}$) for the $\text{diendo}$ derivatives.     

Cycloaddition of single oxygen and triazolinedione (TAD) with spirocyclopentadienyl-1,3,5-cycloheptatrienes1: tropilidene versus norcaradiene reactivity

4-Methyl-1,2,4-triazoline-3,5-dione (MTAD) gives with 7-spiro-fluorenyl-1,3,5-cycloheptatriene ($\text{1d}$) initially he norcaradine-type urazole ($\text{N3d}$) which at ambient temperatures rearranges into ($\text{6d}$), while ¹0₂ gives the tropilidene-type endoperoxide ($\text{T4d}$).     

The crystal structure of hexathallium(I) hexatellurodigermanate(III), Tl6[Ge2Te6]

The new compound Tl₆[Ge₂Te₆] was prepared by thermal synthesis from the elements. The material is triclinic, space group $\text{P}\text{1}$, with a = 9.471(2), b = 9.714(2), c = 10.389(2) Å, α = 89.39(1), β = 97.27(1), γ = 100.79(1)°, and Z = 2. The crystal structure was determined from single-crystal intensity data measured by means of an automated four-circle diffractometer and refined to an R value of 0.053 for 1831 observed reflections. Tl₆[Ge₂Te₆] is characterized by Ge₂Te₆ units with GeGe bonds which are linked into a three-dimensional structure by Tl atoms coordinated to essentially six Te atoms. The most important mean distances are $\text{d}\text{GeGe}\text{) = 2.456}$ Å, $\text{d}\text{(}\text{GeTe}\text{) = 2.573}$ Å, and $\text{d}\text{(}\text{TlTe}\text{) = 3.515}$Å. The lone 6s electron pairs of the thallium(I) atoms exhibit significant stereochemical activity. Tl₆[Ge₂Te₆] represents a new structure type.     

Stereo- and regioselective methods for the synthesis of three consecutive asymmetric units found in many natural products

Regio- and stereoselective methods are described for the synthesis of compounds possessing the stereochemistry of type $\text{1a}$, $\text{1b}$, $\text{1c}$, and $\text{1d}$ from the aldehyde $\text{2}$.     

On the mechanism of the formation of benzocyclobutene by flash vacuum pyrolysis of ortho-methylbenzyl chloride

Flash vacuum pyrolysis of $\text{o}$-methylbenzyl chloride-$\text{∝}$,$\text{∝}$-$\text{d}$₂ gives benzocyclobutene-$\text{∝}$,$\text{∝}$-$\text{d}$₂. This finding indicates that the reaction involves net δ-elimination of hydrochloric acid.     

Organoboranes in organic synthesis: IX. Carbonylation products of organoboranes derived from myrcene

Myrcene and thexylborane react in the ratio $\text{2}\text{3}$ to give a mixture of two boranes, only one of which is carbonylated with cyanide/trifluoroacetic anhydride, followed by oxidation, to give 3-hydroxymethyl-6-isopropyl-2-methylcyclohexanone (A). The positions of hydroboration are established by synthesis of the hydroboration/oxidation products. The cyanidation of the organoboranes derived from myrcene and diborane leads to a $\text{2}\text{3}$ mixture of A and 5-(2′-hydroxyethyl)-2-isopropylcyclohexanone, the structures of which are established by independent synthesis. The hydroboration of myrcene is shown to be relatively non-stereospecific.