Aldosulose

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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