D-Galactofuranose

Deoxy-D-jcylo hexose 6-(dihydrogen phosphate) (21) has also been synthesized (2) the reaction sequence makes use of 3-deoxy l 2,5 6-di-O-isopropylidene D-galactofuranose (16), a compound that can be easily prepared from D-glucose (2, 60). The mono-isopropylidene derivative (17) formed by partial hydrolysis of the di-ketal is converted into the 6-tosylate (18) by reaction with one molar equivalent of p-toluenesulfonyl chloride. From this the epoxide (19) is formed by reaction with sodium methoxide. Treatment of the anhydro sugar with an aqueous solution of disodium hydrogen phosphate (26) leads to the 6-phosphate (20)... 

The failure of a compound to undergo periodate oxidation can not be regarded as positive proof that it contains no 1,2-glycol structures. If the glycol is securely locked in a trans position, oxidation has been shown not to occur. This resistance has been encountered in the bicyclic anhydro hexoses, for example, l,6-anhydro-/3-D-glucofuranoseM and 1,6-anhydro-a-D-galactofuranose.54 This work has already been summarized in this... 

Another example of the fact that primary displacement of sulfonic esters is not always facile101,103-105 is the discovery that vigorous conditions were required for fluorination of l,2 3,5-di-0-isopropylidene-6-0-(methylsulfony])-a-D-galactofuranose with potassium fluoride dihydrate in methanol,85,88 and a comparatively long reaction-time was necessary for the fluorination of the 6-O-p-tolylsulfonyl derivative with tetrabutylammonium fluoride in acetonitrile.106... 

O-trityl-D-gaIactono-1,4-lactone (30c). Detritylation of 30c with F3B OEt2 caused 0-5 —> 0-6 acetyl migration, affording 30b, which was used for the preparation of 5-O-methyl-D-galactofuranose (39). 

As the conductivity of the equilibrium mixture in 0.5 M boric acid amounts to about 65 units, the quantities of D-galactofuranoses are smaller than for D-glucose solutions, but on the other hand the mutarota-tion proceeds somewhat more rapidly. It may also be observed that in pure water both isomers also show a gradual increase in conductivity, which however is much less than in 0.5 M boric acid. 

Addition of dichloromethylene to 3-deoxy-l,2 5,6-di-0-isopropyli-dene-a-D-erythro-hex-3-enofuranose gives 3-deoxy-3,4-C-(dichloro-methylene)-l,2 5,6-di-0-isopropylidene-a-D-galactofuranose.51 [The... 

Several routes to 1-deoxygalactonojirimycin (5) have been published to date. l,5-Dideoxy-l,5-imino-D-galactitol (5), the epimer of 1-deoxynojirimycin (1) at C-4, was first synthesized by Paulsen and co-workers in 1980 [24]. These workers employed 1,6-anhydro- a-D-galactofuranose (6) as the starting material. 

The isomeric /3-D-galactofuranose pentaacetate gives rise to fragment E, by cleavage of the C-4 to C-5 bond, and, therefore, the ion has a lower mass number ... 

For the preparation of a 3 -deoxy Lex analogue, an acylated 3-deoxy-D-. v/o-hexopyranose was used. The latter was prepared either from phenyl 1-thio-D-galactopyranoside78 or from l,2 5,6-di-0-isopropylidene-a-D-galactofuranose,79 via the Barton and McCombie deoxygenation method. 

Selective tosylation of 1,6-anhydro-a-D-galactofuranose (167) is favored for position C-3 because of steric accessibility and affords tosylate 51. Treatment of 51 with base results in intramolecular displacement of the tosyloxy group by 5-hydroxyl group with the formation of 1,6 3,5-dianhydro-a-D-gulofuranose (168) the reaction involves closure of the oxetane and not the oxirane ring.246... 

P. Koll, Darstellung der 1,5-Anhydro-u-D-galactofuranose durch Vakuumpyrolyse von D-Galactose, Chem. Ber., 106 (1973) 3559-3564. 

P. Koll, J. Schulz, and U. Behrens, 1,6-Anhydrofuranosen. 9. Selektive Monotosylierung der 1,6-Anhydro-a-D-galactofuranose. Synthese und Bestimmung der Molekulstruktur der l,6 3,5-Dianhydro-a-D-gulofuranose, Chem. Ber., 112 (1979) 2068-2078. 

Since the course of chromogen formation involves 2-acetamido-2-deoxy-D-glucofuranose or 2-acetamido-2-deoxy-D-galactofuranose as an intermediate, the failure of alkali-stable glycopyranosides to respond to the test is understandable. An alkali-stable 4-O-substituent will likewise prevent fu-ranose formation it has been observed that (a) methylated derivatives of... 

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