Sugars 3-deoxy

A new trideoxy disaccharide (1) has been isolated from tenacissima 

Reagents i, p-NOjC H OCHO ii, POClj-EtjN iii, BujSnH 

Photolytic decarbonylation of several 6-deoxy-o -L-/yxo-hex-4-ulopyranosides, and related C-glycosides, yielded mainly the 5-deoxy-j3-D-ribofuranosides.  

Methyl glycosides and the 1,2-0-isopropylidene derivative of 4-deoxy-DL-t/zreo-pentose have been prepared by standard reactions.  

A synthesis of ascarylose (3,6-dideoxy-L-arfl6mo-hexose) from 3,6-dideoxy-L-erythro-hexos-2 lose is reported by base-catalysed rearrangement of the 2-ulose to 3,6-dideoxy-L-iflra6mo-hexono-l,4-lactone followed by reduction with sodium bis(2-methoxyethoxy)aluminium hydride.  

Several references to deoxy derivatives of amino-sugars are given in Chapter 8. 

A new method of preparing deoxy-sugar derivatives involves treatment of a-nitro-epoxides with sodium borohydride in this way, for example, compound (1) gives the 5-deoxy derivative (2), and (3) gives (4). However, 

3-deoxy-phenyl glycosides by direct C—O cleavage of the sulpnonates. Epoxide intermediates were shown not to be involved.  

A series of 3-deoxy compounds derived from methyl a-o-glucopyranoside were obtained via iV,iV-dimethylsulphamoyl esters which underwent efficient reductive cleavage on treatment with sodium in liquid ammonia under conditions in which acetal, ester, acetamide, and azido groups were stable. The required esters were prepared by use of V,A-dimethylsulphamoyl chloride, or with sulphuryl chloride in pyridine, followed by dimethylamine. Other 

Synthesis of D-epiallomuscarine, a 2,S-anhydro-3,6-dideoxyaldonic acid derivative, is detailed in Chapter 23. Paratose (3,6-dideoxy-D-r/i o-hexose) has been prepared from the 3-deoxy compound (13) by selective hydrolysis, tosylation at the primary position, and reduction using lithium aluminium 

Barton and Subramanian have reported a procedure for the synthesis of deoxy-sugars and -nucleosides based on opening of diol thiocarbonates in a radical fashion using tributyltin hydride (c/., Vol. 9, p. 86). For example, the thiocarbonates (197) and (198) were cleaved regioselectively (secondary radical more stable than primary radical) to give, after alkaline hydrolysis, 5-deoxy-1,2-0-isopropylidene-3-O-methyl-a-D-xy/o-hexofuranose (57%) and methyl 4-deoxy- 

3- thiocarbonates (199) and (200) afforded mixtures of the corresponding 2-deoxy-(30% and 60%, respectively) and 3-deoxy-sugars (60% and 40%, respectively). 

An efficient method for the deoxygenation of protected keto-sugars to give deoxy-sugars involved treatment with phosphorus pentasulphide in pyridine and reductive desulphurization of the products, whose nature varied with the 

5-deoxy-L-arabinose into L-fry// ro-biopterin, a naturally occurring pteridine that is widely distributed in micro-organisms, insects, algae, amphibia, and mammals. 6-(D-flrfl6mo-Tetrahydroxybutyl)- and 6-(D-// reo-trihydroxypropy1)- 

The preparation of methyl jS-L-rhamnopyranoside and the synthesis of (I - 2)-linked disaccharides containing non-reducing residues of 6-deoxy-D-glucopyranoseand of 3-0-a-L-rhamnopyranosyl-D-glucose have been noted in Chapter 3. 

Deoxy prefixes with a frontal locant are considered as detachable, therefore ordered alphabetically and used indiscriminately both for trivially and for systematically named sugars. In assigning the pertinent configurational descriptors, interposed CH2 (and also CO) groups are again disregarded. 

Lithium triethylborohydride reductions of tosylate derivatives of methyl 4,6-0-benzylidene-a-D-glucopyranoside were highly regio-selective and gave good yields of deoxy-sugars via epoxide intermediates thus, the 3-mono- and 2,3-dl-O-tosylates gave the same 

2- deoxy-D-rlbo-hexopyranoside, while the 2- -tosylate provided Its 

Carbon radicals are markedly stabilized by oxygen atoms bonded to the S-carbon, so that radical reactions, such as tributyltln hydride reduction of 0-thlocarbonyl and Isonltrile derivatives, proceed in many carbohydrate derivatives to give deoxy-sugars, while not proceeding in model compounds devoid of g-oxygen functionality. That the 3-oxygen could be part of another ring was evident from 

Tertiary hydroxy groups adjacent to formyl groups in branched-chaln sugars can be replaced by hydrogen through free-radical deoxygenation of the benzoate, or even better the 4-cyanobenzoate, 

2-Bromo-2-deoxy-sugars, derived from glycals, can be photo-chemlcally converted into 2-deoxy-sugars on irradiation in 2-propanol thus compound (13) was obtained from bromide (1 ). Photolytic de-iodination was utilized in a synthesis of L-streptose (Chapter 13). 

A novel method for the reductive deamination of amino-sugars has been published by Barton s group. The process involves sequential iV-formylation, dehydration to the isocyano-derivative, and reduction with tributylstannane. Application of the reaction to l,3,4,6-tetra-C -acetyl-2-amino-2-deoxy-/3-D-gluco-pyranose afforded 2-deoxy-D-glucose tetra-acetate in 72% yield. 

A new synthesis of 2-deoxy-D-a/-aZ /no-hexose (6) uses 2,3 4,5-di-0-iso-propylidene-D-arabinitol (7) as starting material. The acetal was converted into the 1-cyano-derivative (8) via the 1-O-triflyl ester (9). Partial reduction of (8) 

Zdlyomi, D. Banfi, and J. Kuszmann, Acta Chem. Acad. Sci. Hung., 1979, 101, 323. 

The acid-catalysed addition of phenol to 3,4,6-tri-O-acetyl-D-galactal afforded phenyl 3,4,6-tri-0-acetyl-2-deoxy-0 -D-/yxo-hexopyranoside which was nitrated with nitric acid in a mixture of acetic acid and acetic anhydride to give the p-nitrophenyl glycoside.  

L-Ascarylose (3,6-dideoxy-L-xy/o-hexose) has been synthesized from L-rhamnono-1,5-lactone, Benzoylation of the lactone in pyridine resulted in elimination of the 3-substituent to give (24). Subsequent hydrogenation of (24) was highly stereoselective, giving the 3,6-dideoxy-lactone (25) in 90% yield from which L-ascarylose and several of its derivatives were prepared.  

The drawback of this method arises from the rearrangement of glycals, under the acidic conditions of the reaction, to the 2,3-unsaturated enoses (Ferrier reaction). The other problem is the incompatibility of some acid-labile protective groups with the relatively strong reaction conditions. These difficulties led to the development of different methodologies with the aim of minimizing the 

Other mild reagents have been introduced, among them BC13, BBr3,35 BF3 Et20,36 a rhenium(V)-oxo complex,37 and palladium complexes.38 Flydroxy-mercuration with mercury(II) acetate in aqueous tetrahydrofuran, followed 

LaCl3 7H20-NaI-benzyl alcohol was also reported for the same reaction, and it was used for the synthesis of 1,6-dideoxynojirimycin.42 

The absence of a substituent at C-2, usually able to influence the course of the glycosylation reaction, impedes control of the a (3 ratio. Marzabadi and Franck have compiled extensive data on the relevant glycosylation methods for 2-deoxy sugars.3 

Several methods were reported for the selective synthesis of a-glycosides in the absence of a controlling group at C-2. The 2-deoxy sugar is first converted into a glycosyl donor by formation of phosphites,53 phophonodithioates,54 or phosphinothioates,55 which react with different acceptors and promoters. 

The anomeric carbon of a furanose or pyranose form of a ketose bears both a hydroxyl group and a carbon substituent. In the case of 2-ketoses, this substituent is a CH2OH group. As with aldoses, the anomeric carbon of a cyclic hemiacetal is readily identifiable because it is bonded to two oxygens. 

A commonplace variation on the general pattern seen in carbohydrate structure is the replacement of one or more of the hydroxyl substituents by some other atom or group. In deoxy sugars the hydroxyl group is replaced by hydrogen. Two examples of deoxy sugars are 2-deoxy-D-ribose and L-rhamnose  

The hydroxyl at C-2 in D-ribose is absent in 2-deoxy-D-ribose. In Chapter 27 we shall see how derivatives of 2-deoxy-D-ribose, called deoxyribonucleotides, are the fundamental building blocks of deoxyribonucleic acid (DNA), the material responsible for storing genetic information. L-Rhamnose is a compound isolated from a number of plants. Its carbon chain terminates in a methyl rather than a CH2OH group. 

SAMPLE SOLUTION (a) The hydroxyi group at C-3 in D-ribose is replaced by hydrogen in 3-deoxy-D-ribose. 

For a review of the isolation of chitin from natural sources and some of its uses, see the November 1990 issue of the Journal of Chemical Education (pp. 938-942). 

Reagents i, BujSnH-refluxing PhMe ii, NaOH iii, AcjO-py 

Photolysis of solutions of acetic and pivalic esters in aqueous HMPT also resulted in deoxygenation for example, photolysis (A 254 nm) of methyl 4-0-acetyl-2,3-0-isopropylidene-a-L-rhamnopyranoside and 1,2 5,6-di-0-isopropylidene-3-0-pivaloyl-a-D-glucofuranose gave the corresponding 4- and 3-deoxy derivatives, respectively, in yields of 70 and 75 The method was also extended to hexoses 

Deoxygenation, of sugars can also be achieved by way of thio-sugar precursors, which can be desulphurized with Raney nickel or sodium in liquid ammonia or tributyltin hydride. This approach has been used to synthesize methyl 2-amino-2,3-dideoxy-4,6-0-isopropylidene-a-D-ribo-hexopyranoside (278) from the 3-S-phenylthio-a-D-allopyranoside obtained when the 3-triflate (279) reacted with sodium benzenethiolate at 5°C—in this instance, desulphuration was best achieved with sodium in liquid ammonia.  

Mizuno, Y. Harada, and Y. Okamura, Shizuoka Daigaku Nogakubu Kenkyu Hokoku, 1976, 26,45 

Reagents i, NaNOj-AcOH ii, SO Clj iii, HC=CCH(OMe)j-EtMgBr-CuCl iv, H -Pd-BaSO V, HO vi, H3PO.j-CC1 vii, H -Pd-C viii, LiAlH ix, BnCl-HO x, MeOH-TsOH 

The shells of lobsters are mainly chitin, a polymer of /V-acetyl-D-glucosamlne. 

Reagents i, di-imidazol-l-yl thione ii, Mel iii, Cr(OAc)2-BuSH-DMF iv, MeONa-MeOH 

A series of l,6-anhydro-2- and -3-deoxy-D-hexopyranoses has been prepared by reductive ring-opening of appropriate oxirans. In a procedure for the synthesis of 3-deoxyaldoses, the monosaccharide benzoylosazone was converted into the 3-deoxyaldosulose by treatment with an aromatic amine base-catalysed 

Tanaka and T. Nakamura, Chuo Daigaku Rikogakuba Kiyo, 1974, 17, 175 (Chem. Abs., 1975, 83, 131 849v). 

Murakami, N. Tanaka, T. Tezuka, and C.-M. Chen, Chem. and Pharm. Bull. Japan), 1975, 23,1634. 

5-Deoxy-L-arabinose has been prepared from l,2 5,6-di-0-isopropylidene-oe-D-glucofuranose by way of the alkenic derivative (205), and an oxymercuration- 

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

Sections Structurally modified carbohydrates include deoxy sugars, ammo sugars,... 

Deoxy sugar (Section 25 10) A carbohydrate in which one of the hydroxyl groups has been replaced by a hydrogen... 

The maciocyclic lactone of all avermectins has an a-L-oleandtosyl-a-L-oleanchosyloxy substituent at carbon 13, which is a 2-deoxy sugar glycoside. 

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). 

FIGURE 7.12 Several deoxy sugars and ouabain, which contains a-L-rhamnose (Rlia). Hydrogen atoms highlighted in red are deoxy positions. 

T he last five years have witnessed a reawakening interest in modem carbohydrate chemistry, a feature which is reflected in the number of symposia held by the Division of Carbohydrate Chemistry during national meetings of the American Chemical Society. The scheduling of a symposium on Deoxy Sugars for the fall meeting of 1966 seemed very opportune if not somewhat overdue. 

Finally I would like to express my sincere thanks to all the participants in this first symposium on Deoxy Sugars, and acknowledge the cooperation to those who were able to contribute to this monograph. 

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