Aldosuloses

The preparation and chemical properties of levoglucosenone as well as its use in the total synthesis of natural products have been reviewed, and the stereoselective reduction of 3-bromolevoglucosenone to l,6-anhydro-3-bromo-3,4-dideoxy-P-D-rAreo-hex-3-enopyranose 1 has been effected using zinc borohydride. The known lactone 2 has been converted into the aldosulose derivative 3, a degradation product from the ansamycin antibiotic (+)-trienomycin A. This confirmed that the fragment of the natural product was the enantiomer of 3.  

An improved synthesis of l,6-anhydro-2,3-di-0-benzyl-P-D-x7/o-hexopyranos-4-ulose involves 1,6-anhydride formation from methyl 2,3-di-O-benzyl-a-D-gluco-pyranoside and subsequent Swem oxidation.  

Use of the enzyme dTDP-glucose-4,6-dehydratase on the substrate dTDP-glucose has generated the corresponding 6-deoxy-4-keto product - but it partly isomerized to the 3-keto compound during workup. 3-Azido-3-deoxy- and 3-deoxy-dTDP-glucose were also substrates affording the 3-modified 6-deoxy-4-keto products.  

Ozonolysis of the model compound methyl 4-O-ethyl-p-D-glucopyranoside has led to authentic samples of methyl, 3,6-di-0-acetyl-4-0-ethyl-P-D-arafei/io-hexo-pyranosid-2-ulose, methyl 2,6-di-0-acetyl-4-0-ethyl- 3-D-rifco-hexopyranosid-3-ulose, and methyl 2,3-di-0-acetyl-4,0-ethyl-P-D-glucohexodialdo-l, 5-pyranoside. The isomerization of 2-oxo- and 3-oxo-glycosides in pyridine has been elucidated. Methyl a-D-aroZ i/u -hexopyranosid-2-ulose 4 undergoes an intramolecular hydride shift leading to the a-D-arai OTo-hexopyranosid-3-ulose 5 which then converts to the thermodynamically more stable a-D-r/Z o-isomer 7 via an enediol intermediate 6 which also forms directly from 4 to a lesser extent. The 

Carbohydrate Chemistry, Volume 30 The Royal Society of Chemistry, 1998 

Glycosid-2-ulose derivatives mesylated at 0- 1 give access to enolones, e.g. (1), from which glycosid-3-ulose compounds, e,g. 

The glycosld-3-ulose derivative (iJ) was obtained from the corresponding D-ldo-alcohol by use of acetic anhydride - DMSO for h. When, however, this was extended to days the doubly branched product (5) was obtained, by sigmatropic rearrangement of the intermediate (6).  

The potentially valuable observation has been made that treatment with bromine of per- -tributylstannyl derivatives of methyl 

The oxidation of 1,2 5,6-di- -lsopropylidene-a-D-glucofuranose with acetic anhydride-DMSO is improved when the reagents are pre- 

Collins and coworkers have continued their studies of photochemical reactions of aldosulose derivatives. Pyranos-3-uloses 

Nlcotinlum dlchromate (made from nicotinic acid and chromium trioxide and used in benzene-pyridine) has been recommended as a new and Inexpensive reagent for the efficient and large scale oxidation of the hydroxy groups in such compounds as 1,2 5,6-di-O-Isopropylldene-a-D-glucofuranose and 1,2 3,4-di-O-lsopropylidene-a- 

The 4-ene (9) which is obtained by thermal or base-catalysed isomerization of the 5-ene (8), on treatment with acetic acid in 

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Multiple sets of chiral centres 2-Carb-I2. Ketoaldoses (aldoketoses, aldosuloses)... 

Fig. 4. Sugar derivatives serving as acceptors for glycosylation by dextransucrase alditols, aldosuloses, aldonic acids, a fructose dianhydride, and a glycal.71...

Another 2,3-bis(phenylhydrazone), namely, l,5 4,6-dianhydro-2,3-hexodiulose bis(phenylhydrazone) (62a), was also found to cyclize to a pyrazoline (63a) by the action of copper(II) sulfate or benzalde-hyde, which usually convert osazones into aldosuloses or osotria-zoles.65 Reduction of this bicyclic compound (63a) led to the pyrazo-lidine 64, and periodate oxidation of 63a gave the expected aldehyde 65. 

This conversion of readily available 2-furyl alcohols into unsaturated pyranosuloses proved a very effective route to racemic monosaccharides, through stepwise, selective functionalization of the enone grouping in 325. The shortest synthesis of a natural compound by following this scheme involves palladium-catalyzed hydrogenation of the aldosulose (325, R = Me) obtained from l-(2-furyl)ethanol, resulting209 in cinerulose A, the sugar component of the antibiotic cine-rubin. 

The substantial progress made in synthesis of the complex carbohydrates occurring in medicinally important molecules68-72 is largely due to the discovery of new oxidative procedures that permit ready preparation of aldosuloses. Branched-chain sugars were obtained by nucleophilic additions to various lcetopentoses and ketohexoses subsequent condensation with purines and pyrimidines then afforded the desired natural, or synthetic, antibiotics (see, for example, Refs. 19 and 73). 

D. Horton and J. S. Jewell, Specific labeling of sugars through enolization of aldosulose derivatives. Synthesis of 1,6-an hyd ro-/i-i)-talopy ranosc, Carbohydr. Res., 3 (1966) 255-257. 

These compounds are formally derived from aldoses by oxidation of a secondary hydroxyl group to a ketone group. The well-known aldos-2-uloses (usually termed simply aldosuloses or osones in former usage) have long been known in the form of their bis(hydrazone) derivatives, the osazones. Deoxyaldosuloses have been implicated as intermediates in a variety of degradation reactions. Aldos-3-, -4-, and -5-uloses have been prepared, principally as intermediates for synthesis. 

Lactone 227 has been converted in several steps into aldosulose derivative 228, a degradation product from the ansamycin antibiotic (+ )-trienomycin A.441... 

Crystalline 1,2 2,3 5,6-tri-0-isopropylidene-2(2 )-o -D-araZ) o-hexofura-nos-2-ulose (237), prepared by acetonation of 205, is useful for purification of the aldosulose, as it can be hydrolyzed, regenerating 205.455 Aldos-2-ulose 1,1-dithioacetals have also been obtained crystalline.456... 

S. Bayne, Aldosuloses (Osones), Methods Carbohydr. Chem., 2 (1963) 421-430. 

Uloses are derivatives of carbohydrates, which contain a further keto group. Aldosuloses are obtained from aldoses and diuloses from ketoses. They are important intermediates in the synthesis of carbohydrates. Uloses can be prepared by oxidation of derivatives in which all the hydroxyls except that one subjected to oxidation are blocked. Uloses are formed as intermediates during pulp bleaching (see Section 8.1.3). 

Aldosulose derivatives having unprotected ketonic functions have been converted into similarly substituted ethylene dithioacetals by the action of 1,2-ethanedithiol in the presence of boron trifluoride. l,6-Anhydro-2,4-dideoxy-jS-D-glt/cero-hexopyranos-3-ulose70 (9)... 

Thus in the Ruff degradation, for example of o-glucose to o-arabinose, the aldose is oxidized electrolytically to the aldonic acid and this on treatment with hydrogen peroxide and ferric acetate affords the 2-ketoaldonic acid (aldosulose), which yields D-arabinose by loss of carbon dioxide. The yield of aldopentose from the aldonic acid... 

Aldosuloses (sugar osones) also reacted with 624 to afford mixtures of... 

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