Mannurone 3,6-lactone

Nowadays, no saturated or unsaturated mannuronic acid derivatives are commercially available in a monomeric form, thereby limiting their uses in chemical synthesis. In contrast to o-glucuronic, o-galacturonic, or L-iduronic acids, only the D-mannurone lactone form (D-mannofuranurono-6,3-lactone) was available for... 

In model experiments,205 it was found that concentration of an aqueous solution of the aldonic acids in the presence of hydrochloric acid gives exclusively the 1,4-lactones, which, on subsequent trimethyl-silylation, give only one peak on the chromatogram. This method was successfully employed for the separation of D-galacturonic, D-glucuronic, and D-mannuronic acids. Of the 1,4-lactones examined, only the trimethylsilyl ether of D-mannono-1,4-lactone was obtained in crystalline form. However, all of the derivatives showed characteristic differences in their infrared spectra in the range of 1500 to 600 cm"1. When this method was applied to the determination of uronic acids in a variety of polysaccharides,205 it was impossible to find any hydrolytic conditions under which the uronic acids were quantitatively released and then reduced, a problem experienced by other workers.20 The method was, however, successful in affording a qualitative, microscale procedure for the identification of hexuronic acids (which otherwise are difficult to detect). 

Whereas mannuronic and galacturonic acids exist in both a- and /3-d-pyranoid forms, glucuronic acid is only found in the /3-d form. Glucuronic and mannuronic acids form crystallizable lactones, but that of galacturonic acid has not yet been crystallized. On isolation, D-glucuronic acid appears as needle-like crystals of /3-D-glucopyranuronic acid (I), which is... 

Improvements were made by Frush and Isbell (79) in the sulfuric acid-hydrolysis method of isolating mannuronic acid lactone from alginic acid. Spoehr (236) reported a new method for the isolation of the lactone depending on hydrolysis with formic acid. The authors have found that the formic acid method, with modifications, is adaptable to the production of mannuronic acid lactone. 

Q, How does one get a good yield of mannuronic acid lactone from alginic acid using the Spoehr procedure, which I believe employs formic add for hydrolysis Is alginic acid stable under acid treatment ... 

O-p-D-Mannopyranuronosyl-D-glucose, M-l 12 4-0-p-D-Mannopyranuronosyl-D-mannuronic acid, M-113 Mannourono-6,3-lactone a-D-Pyranose-/< mi Me glycoside, M-122 Mannourono-6,3-lactone p-D-Pyranose-/< mi Me gtycoside, M-122 Mannuronic acid D-form, M-l23... 

D-Glucuronic acid D-Glucurono-y-lactone D-Galacturonic acid D-Mannuronic acid D-Mannurono-y-lactone D-Glucaric acid D-Glucaro-l,4-lactone D-Glucaro-6,3-lactone... 

Mannurone has been shown to have a 1,4-hemiacetal ring and a 3,6-lactone ring with periodic acid, only the unblocked hydroxyls at carbons 1 and 2 are attacked, and D-araburonic acid is the product 117). 

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