scholarly journals A MECHANISM FOR THE ANOMERIZATION OF ACETYLATED ALKYL GLYCOPYRANOSIDES

1955 ◽  
Vol 33 (1) ◽  
pp. 120-127 ◽  
Author(s):  
R. U. Lemieux ◽  
W. P. Shyluk
Keyword(s):  
Boron Trifluoride ◽  
Titanium Tetrachloride ◽  
Ion Pair ◽  
Methoxyl Group ◽  
Racemic Mixture ◽  
Unsuccessful Attempt ◽  
Glycosidic Cleavage ◽  
Carbon 14 ◽  
Intramolecular Mechanism

Unequivocal evidence that the anomerization of acetylated alkyl glycopyranosides can proceed by way of an intramolecular mechanism was obtained through the observation that a racemic mixture of methyl β-glucopyranoside tetraacetate with the D-isomer labelled in the methoxyl group with carbon-14 is anomerized both by titanium tetrachloride and boron trifluoride without transfer of radioactive methoxyl groups to the L-isomer. It is submitted that these intramolecular anomerizations are best rationalized as the result of an unsuccessful attempt by the environment to bring about glycosidic cleavage and proceed by way of an ion-pair intermediate in which the anion is derived from the aglycon group.

Synthesis of 5-Substituted 2-Pyrrolidinones by Coupling of Organozinc Reagents with Cyclic N-Acyliminium Ions

Synthesis ◽  
2019 ◽  
Vol 51 (24) ◽  
pp. 4650-4656
Author(s):  
Ivann Zaragoza-Galicia ◽  
Zaira A. Santos-Sánchez ◽  
Yazmín I. Hidalgo-Mercado ◽  
Horacio F. Olivo ◽  
Moisés Romero-Ortega
Keyword(s):  
Diethyl Ether ◽  
Boron Trifluoride ◽  
Titanium Tetrachloride ◽  
Reaction Medium ◽  
Coupling Reaction ◽  
Acyliminium Ions ◽  
Organozinc Reagents ◽  
Ether Complex ◽  
Organozinc Reagent

A coupling reaction between cyclic N-acyliminium ions with organozinc reagents is described. The cyclic N-acyliminium ions, generated in situ from N-substituted-5-hydroxy-2-pyrrolidinones by treatment with boron trifluoride–diethyl ether complex or titanium tetrachloride, are trapped by the organozinc reagent, which is formed from an alkyl bromide in the presence of zinc in the same reaction medium. The N-substituted-5-allyl-2-pyrrolidinones generated using this method serve as versatile intermediates for the synthesis of azabicyclic systems with indolizidine and pyrroloazepinolizidine cores.

HYDROGENOLYSIS OF CARBOHYDRATES: VII. METHYL β-L-ARABOPYRANOSIDE-1-C14

1959 ◽  
Vol 37 (8) ◽  
pp. 1229-1234 ◽  
Author(s):  
Thomas Francis ◽  
A. S. Perlin
Keyword(s):  
Ring Opening ◽  
Oxide Catalyst ◽  
Reductive Cleavage ◽  
Equimolar Mixture ◽  
Methoxyl Group ◽  
Hydroxyl Groups ◽  
Ether Cleavage ◽  
Carbon 14 ◽  
Chrome Oxide ◽  
Cis And Trans

Methyl β-L-arabopyranoside-1-C14 was hydrogenolyzed in the presence of copper chrome oxide catalyst at 250 °C, yielding an approximately equimolar mixture of optically inactive cis- and trans-3,4-dihydroxytetrahydropyran-C14, together with 2,3-dihydroxypentane-C14. The latter was formed by reductive ring-opening of the tetrahydropyrandiols. Ether cleavage of each of the cyclic diols afforded 1,2,3,5-tetrahydroxypentane-C14 in which the tracer was distributed about equally between carbons 1 and 5. Carbon-14 in the pentanediol was distributed in a similar manner. The results show that both the 2- and 4-hydroxyl groups of the original pentoside are prone to reductive cleavage, and that cis- and trans-glycol groups in the cyclic diols are formed by isomerization. They suggest that hydrogenolysis of the methoxyl group takes place initially, accompanied by isomerization, to give a mixture of tetrahydropyrantriols in which the 2- and 4-hydroxyl groups have equivalent reactivity.

A general route to the synthesis of 3-alkylidene derivatives of 4-thiochromanone 1,1-dioxide

1984 ◽  
Vol 62 (11) ◽  
pp. 2535-2539
Author(s):  
Ian W. J. Still ◽  
Fred J. Ablenas
Keyword(s):  
Carbonyl Compounds ◽  
Lewis Acids ◽  
Boron Trifluoride ◽  
Titanium Tetrachloride ◽  
Enol Ethers ◽  
Mild Conditions ◽  
Condensation Products ◽  
Derivatives Of

The reactions of the trimethylsilyl enol ethers of both 4-thiochromanone and 4-thiochromanone 1,1-dioxide with various carbonyl compounds complexed with titanium tetrachloride give moderate yields of the previously unknown 3-alkylidene condensation products under mild conditions. Other Lewis acids, with the exception of boron trifluoride, were found to be ineffective in this transformation.

Determination of carbon-14 in the methoxyl group of organic compounds

1968 ◽  
Vol 40 (8) ◽  
pp. 1183-1186 ◽  
Author(s):  
Mitsuo. Chubachi ◽  
Eiko. Kawano ◽  
Masayuki. Hamada
Keyword(s):  
Organic Compounds ◽  
Methoxyl Group ◽  
Carbon 14

Fine Structure of Cytochalasin Induced Polyploid Cells

1968 ◽  
Vol 26 ◽  
pp. 122-123
Author(s):  
Awtar Krishan ◽  
Nestor Bohonos
Keyword(s):  
Fine Structure ◽  
Cytochalasin B ◽  
Present Report ◽  
Cell Monolayer ◽  
Polyploid Cell ◽  
Specific Cell ◽  
Nuclear Surface ◽  
Unsuccessful Attempt ◽  
Daughter Cells ◽  
Polyploid Cells

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).

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