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.

PREPARATION OF ERUCIC AND NERVONIC ACIDS LABELLED WITH CARBON-14

1957 ◽  
Vol 35 (8) ◽  
pp. 757-760 ◽  
Author(s):  
K. K. Carroll
Keyword(s):  
Enoic Acid ◽  
Nervonic Acid ◽  
Malonic Ester ◽  
Ester Synthesis ◽  
Trans Isomers ◽  
Carbon 14 ◽  
Cis And Trans Isomers ◽  
Cis And Trans

The malonic ester synthesis of nervonic acid (tetracos-15-enoic acid) has been modified so that the product consists of pure cis rather than a mixture of cis and trans isomers. The modified synthesis has been used for the preparation of C14-labelled erucic and nervonic acids.

HYDROGENOLYSIS OF CARBOHYDRATES: V. ISOMERIZATION OF METHYL β-L-ARABOPYRANOSIDE

1958 ◽  
Vol 36 (6) ◽  
pp. 921-925 ◽  
Author(s):  
A. S. Perlin ◽  
E. Von Rudloff ◽  
A. P. Tulloch
Keyword(s):  
Chromium Oxide ◽  
Oxide Catalyst ◽  
Starting Material ◽  
Reaction Conditions ◽  
Copper Chromium ◽  
Cis And Trans

Treatment of methyl β-L-arabopyranoside under hydrogenolytic conditions with copper chromium oxide catalyst induces extensive isomerization. Products formed include glycosides of D-ribose, D-xylose, D-lyxose, and L-lyxose which together represent about an 80–90% conversion of starting material. Isolation of these compounds shows that carbons 2, 3, and 4 undergo isomerization, but no evidence has been obtained of anomerization. These findings possibly explain the formation of an optically inactive mixture of cis- and trans-tetrahydropyran-3,4-diol under slightly more drastic reaction conditions.

Cyclic hydroxycarboxylic acids. III. Tosylation studies on Mono- and Di-hydroxycyclopentanecarboxylates and Mono- and Di-hydroxyprolines

1977 ◽  
Vol 30 (1) ◽  
pp. 131 ◽  
Author(s):  
RP Philp ◽  
AV Robertson
Keyword(s):  
Free Amino ◽  
Heterogeneous System ◽  
Methyl Esters ◽  
Hydroxyl Groups ◽  
Large Excess ◽  
Molar Ratios ◽  
Tosyl Chloride ◽  
Hydroxycarboxylic Acids ◽  
Hydroxy Proline ◽  
Cis And Trans

A large excess of reagent is needed for satisfactory ditosylation of methyl c-2,t-3- and t-2,c-3-di-hydroxycyclopentane-r-1-carboxylates using tosyl chloride-pyridine at 5° overnight. With less reagent, mixtures are produced from which one monotosyl derivative of the t-2,c- 3-series was isolated and its structure proved. By contrast, the methyl cis- and trans-2-hydroxycyclopentanecarboxylates readily tosylate with normal molar ratios of reagent. In the proline series ditosylation of 2,3-trans- 3,4-cis-3,4-dihydroxy-N-tosylproline methyl ester occurs normally in tosyl chloride-pyridine, and so does tosylation of both cis- and trans-4-hydroxy-N-tosylproline methyl esters. On the other hand tosylation of the 3-hydroxy counterparts is very slow, although acetylation of these 3-hydroxyl groups proceeds normally. The O-tosylation results are striking for the lack of pattern. A comparison is also made of O-tosylation accompanying N-tosylation of the free amino acids cis- and trans-3-hydroxy-proline, cis- and trans- 4- hydroxyproline, and the two cis-glycols of 3,4-dihydroxyproline in the heterogeneous system tosyl chloride-ether-aqueous NaOH. Significant O- tosylation occurs in some cases but not in others. This correlation permits assignment of structure to a mono-O-tosyl derivative of a 3,4- dihydroxy-N-tosylproline obtained previously by us.

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