Sugars deoxy, preparation

Benzyl 2-acetamido-6-0-benzyl-2,4-dideoxy-4-fluoro-a-D-glucopyrano-side and the corresponding free sugar were prepared from benzyl 2-acet-amido-3-0-allyl-6-0-benzyl- (or -3,6-di-0-benzyl)-2-deoxy-a-D-galacto-pyranoside by treatment with DAST (in diglyme). 

Several 1 -phosphates of deoxyfluoro sugars were prepared, and their acid-catalyzed hydrolysis was studied. 2-Deoxy-2-fluoro- (580), 3-deoxy-3-fluoro- (582), 4-deoxy-4-fluoro- (583), and 6-deoxy-6-fluoro-a-D-gluco-pyranosyl phosphates (584) were prepared by treatment of the corresponding per-( -acetylated )9-D-glucopyranoses with phosphoric acid [the p anomer (581) of 580 was prepared by a different method]. The first and second ionization constants (pA a, and pA a2) of these compounds were determined potentiometrically, as well as by the F-n.m.r. chemical shifts at a series of pH values, and then the rate constants of hydrolysis for neutral (B) and monoanion (C) were decided. The first-order rate-constants (k) for 580-584 and a-D-glucopyranosyl phosphate (in Af HCIO4,25 °) were 0.068, 0.175, 0.480, 0.270, 1.12, and 4.10 (all as x lOVs), respectively. The rate... 

Several enzymatic procedures have been developed for the synthesis of carbohydrates from acyclic precursors. Aldolases appear to be useful catalysts for the construction of sugars through asymmeteric C-C bond formation. 2-deoxy-KDO, 2-deoxy-2-fluoro-KDO, 9-0-acetyl sialic acid and several unusual sugars were prepared by a combined chemical and enzymatic approach. Alcohol dehydrogenases and lipases have been used in the preparation of chiral furans, hydroxyaldehydes, and glycerol acetonide which are useful as building blocks in carbohydrate synthesis. 

M. Cerny, J. Stanek, Jr., and J. Pacak, Syntheses with anhydro sugars. 7. Preparation of 4-deoxy-D-rifto-hexose (4-deoxy-D-allose), 4-deoxy-D-(yvo-hexose (4-deoxy-D-mannose) and of their 1,6-anhydro derivatives, Collect. Czech. Chem. Commun., 34 (1969) 1750-1765. 

The cyclic acetals have been of great assistance in the preparation of, for example, methylated sugars, - deoxy sugars, and amino-deoxy sugars. The specific syntheses of many di- and tri-saccharides have been described - in these, a suitable acetal of the aldose is caused to react with a poly-O-acetylglycosyl halide or a bromo- or chloro-hydrin derivative. 

Fortunately, we were able to regioselectively tosylate the primary hydroxyl in 42 with p-toluenesulfonyl chloride, triethylamine, and DMAP in dichloromethane at room temperature over 14 h tosylate 63 was isolated in 85% yield. The subsequent nucleophilic displacement with iodide also proceeded satisfactorily delivering the 6-deoxy-6-iodopyranoside 41 in 92% yield. With the desired 6-iodo sugar successfully prepared, we examined its Vasella reductive ring cleavage with Zn dust (size <10 pm) in a 4 1 THF / water mixture at reflux (Scheme 13). A single product was formed according to TLC analysis. However, our H-NMR examination of this product revealed that it was in fact a 1 1 mixture of the two anomeric hemiacetals 40a and 40P formed in 80% yield. 

M. Cerny, I. Cerny, and 1. Pacak, Syntheses with anhydro sugars 27. Preparation of 4-amino-l,6-anhydro-4-deoxy-p-D-glucopyranose— isomerization of 4-amino-1,6-2,3-dianhydro-4-de-oxy-p-D-mannopyranose to l,6-anhydro-3,4-dideoxy-3,4-epimino-p-D-altropyranose, Collect. Czech. Chem. Commun., 41 (1976) 2942-2951. 

A. Yamamoto, C. Miyashita, and H. Tsukamoto, Amino sugars. I. Preparation of Y-acyl derivatives of 2-acetamido-2-deoxy-P-D-glucosylamine, Chem. Pharm. Bull, 13 (1965) 1036-1041. 

The branched-chain sugar 9 (prepared by intramolecular cycloaddition of a terminal deoxy-iV-hydroxyaminopentofuranose bearing a 3-C-prop-2-enyl branch) on UV irradiation afforded a radical observed by ESR spectroscopy. The information obtained was used for configurational and conformational assignments. ... 

Barton s radical deoxygenation procedure has been applied to methyl xanthate derivatives of sugars to prepare methyl 2-deoxy-B-D-... 

Anhydromaltose has been converted to the pseudo-disaccharides (25) containing 3-amino-3-deoxy-epz-inositol or 1-amino-l-deoxy-l-L-myo-inositol via the 6-deoxy-6-nitromaltose derivative (26). The branched-chain unsaturated 6-nitro-sugar (27), prepared conventionally from D-glucose, yielded isomeric dithianyl adducts which were similarly cyclized to give the nitro-cyclitols (28) and (29), of interest as potential intermediates for the synthesis of tetrodo-... 

In this way, for example, by addition of NH3 to the 2,3-epoxides and subsequent epimerization, the following sugars were prepared 3-amino-3-deoxy-D-ribose from L-arabinose and D-xylose 2-amino-2-deoxy-D-allose from 2-amino-2-deoxy-D-glucose , and 2-amino-2-deoxygulose from 2-amino-2-deoxy-D-galactose . 

Methyl glycosides of 2 deoxy sugars have been prepared by the acid catalyzed addition of methanol to unsaturated sugars known as glycals... 

Many pyrazine and quinoxaline syntheses yield mono- or di-N-oxides (76H(4)769). The condensation of a-aminooximes with 1,2-diketones results in the direct formation of pyrazine mono-N-oxides. The a-aminooximes themselves are not easily prepared but 2-amino-2-deoxy sugars readily form the oximes, which have been condensed with glyoxal to yield the pyrazine 4-oxides (Scheme 18) (72JOC2635, 80JOC1693). 

An alternative approach to the use of a-aminoketones involves acetals (72JOC221) and pyrazine-2,3-diones have been synthesized by this route (Scheme 58). The acetals are readily available from the phthalimido derivatives via the a-chloroketones. Hemiacetals have also served as a starting point for pyrazine synthesis, although in most cases hemiacetals are too labile to be easily prepared examples are common in the 2-amino-2-deoxy sugar series 2-amino-2-deoxy-D-glucose for example dimerizes to the pyrazine (101) when generated in situ from the hydrochloride salt (68JAP6813469). 

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-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 vicinal diol groups of deoxy sugar phosphates can be cleaved by periodate in the usual conditions without affecting the stability of the phosphate group, so that this reaction can be used for preparative purposes in certain cases. Thus, if 3-deoxy glucose 6-phosphate (23) is... 

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