Deoxy sugars 5.6- dideoxy

A presentation by Webber and co-workers dealing with the synthesis of fluorodeoxy sugars regrettably had to be left out of this monograph because of unexpected difficulties in the preparation of the manuscript. The fourth aspect was represented in the symposium by two presentations involving important aspects of deoxy and dideoxy sugars by Osborn and Heath respectively which unfortunately were not incorporated in this monograph. 

Deoxy-sugars. Part X. Some Methanesulphonyl and Toluene-p-sulphonyl Derivatives of a-Ethyl-2 3-dideoxy-D-glucoside, S. Laland, W. G. Overend, and M. Stacey, /. Chem. Soc., (1950) 738-743. 

The 2,3,2 -tritosylate 6 produced a complex mixture from which the main products, namely, the new unsymmetrical 2,3 -dideoxy and 3-deoxy sugars 104 and 105 were isolated crystalline, each in 20% yield after chromatography. 

With 2-deoxy-D-glucose-6-phosphate 6 as starting substrate and an additional enzymatic step the synthesis of dTDP-2,6 dideoxy-4-ketoglucose 7, an important intermediate of dTDP-deoxy sugars, and dTDP-P-L-olivose 8 was realized (Scheme 5.2) [68]. 

The conversion of 3-amino-3-deoxy sugars into pyrrolidines requires the presence of a leaving group, such as a p-tolylsulfonyloxy group on C-6 this is exemplified by the conversion of 3-azido-3-deoxy-l,2-0-isopropylidene-6-0-p-tolylsulfonyl-a-D-glucofuranose (44) and methyl 3-azido-2-benzamido-2,3-dideoxy-6-0-p-tolylsulfo-nyl-j8-D-glucopyranoside (46) into the respective pyrrolidines, 45 and 47, by reduction of the azido group, followed by cyclization.37... 

The synthesis of a member of this class of deoxy sugars was accomplished in 1950. The then well-known ethyl 2,3-dideoxy-a-D-en/l/iro-hex-2-enopyranoside was reduced and the product was converted into ethyl 2,3,0-trideoxy-4-O- (methylsulfonyl) -a-D-eryfAro-hexopyranoside by way of the 4,6-dimethanesulfonate. During this work, it was found that, when the dimethanesulfonate of the unsaturated derivative is treated with sodium iodide in the cold, a selective displacement at C-4 occurs, no doubt due to the activated allylic system. The resulting 4-iodo derivative could... 

The paper-chromatographic properties of the common deoxy and dideoxy sugars have been treated in several reviews,2 28 a book,829 and individual publications. Common solvent-systems are 6 4 3 1-butanol-pyridine-water (Solvent A) 4 1 5 1-butanol-acetic acid-water (Solvent B) and 1-buta-nol-ethanol-water (4 1 5, upper phase, Solvent C or 3 1 1, Solvent D). The four 2-deoxy-D-hexoses and the 2,6-dideoxyhexoses may be separated as their borate complexes. 0 The use of 1-butanol-water on the one hand, and of 2-butanone-borate buffer on the other, usually provides adequate separation and, by use of a combination of solvents, these deoxy sugars may be identified. 80 The use of buffered systems has proved highly advantageous in the separation and identification of the isomeric 6-deoxy-hexoses.8 1 Other systems, such as Solvent A and 2 1 2 ethyl acetate-... 

For the 2-deoxy sugars, bond cleavage between C-l and C-2 is retarded probably because the neutral fragment produced at C-2 is a primary radical. This makes 2-deoxy, 2,3-dideoxy, 2,6-dideoxy, etc., sugars especially easy to recognize. Fragments B and C are intense in their spectra, but the dithioacetal fragment, [CH SCjHj) 2] , is absent. 

Prior to 1932, a year of some significance in this field (see p. 191), the reaction was, for example, applied to the preparation of methyl 2,3,4-tri-0-acetyl-6-deoxy-6-iodo-a-D-glucoside348 (25 hours at 130°), 2,3,4,2, -3, 4 -hexa-0-acetyl-6,6 -dideoxy-6,6 -diiodo-trehalose347 (24 hours at 130° 89% yield), and methyl 2,3,4,2, 3 -penta-0-acetyl-6,6 -dideoxy-6,6,diiodo-/3-cellobioside348 (60 hours at 100° 94% yield of product 100% yield of sodium p-toluenesulfonate). Such products are valuable in the preparation of other co-derivatives, e.g., co-deoxy sugars (see p. 157). 

Carbohydrate chemistry is engaged in the synthesis and variation of deoxy sugar chains, where a wide set of protective groups and stereoselective glycosylation techniques are required. This contribution centers on stereoselective syntheses of mono-and oligosaccharides in the field of 2,6-dideoxy- and, in particular cases, branched-chain sugars, and summarizes modem synthetic glycosylation reactions which have been developed for this special kind of carbohydrate chemistry. 

Several deoxy sugars, notably 2-deoxy-D-mY/ o-pentose (2-deoxy-D-ribose) the sugar component of DNA, 6-deoxy-L-mannose (L-rhamnose), 6-deoxy-L-galactose (L-fucose), 6-deoxy-D-glucose (quinovose), and their derivatives, occur very widely in natural products. Also relevant are dideoxy and trideoxy sugars, such as 3,6-dideoxyhexoses, components of the antigenic determinants bacterial... 

A convenient synthesis of ascarylose in four steps starting from L-rhamnono-1,5-lactone (121) was reported.202 The deoxy group in C-3 was introduced through stereoselective hydrogenation of the 2-enonolactone 122 as reported for the preparation of 3-deoxy sugars (see Section III.2). A crystalline furanose derivative of ascarylose, 2,5-di-(3-benzoyl-3,6-dideoxy-a-L-arafo>m-hexofura-nose (125) was also obtained (Scheme 35).203... 

It appears probable that the aldimine II, initially formed by hydrogenation of the nitrile group, is itself in the stabilized, cyclic-hemiacetal form as a 1,2-diamino-l, 2-dideoxy derivative (III), the 1-amino group of which is subsequently hydrolyzed to yield the cyclic 2-amino-2-deoxy sugar (IV) directly.10 10a... 

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