Dialdoses

Reactions of several dlaldose derivatives with furan or 2-methyl- 

Matsuhira, and K.Kanemitsu, Chem. Pharm. Bull., 1985, 33, 4095. 

Compound (17) undergoes interesting changes in stereoselectivity on reaction with different reagents. Whereas methyllithium and methylmagnesium iodide give the alio- and talo-adducts (18) and (19) in the ratio 2-3ilj 2-lithlo-l,3-dithiane affords, almost exclusively, the alloxide (20). Furthermore, with allyltrl- 

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Oxidation of hydioxyl groups to carbonyl groups can form molecules with two aldehyde groups (dialdoses), two ketone groups (diuloses), or an aldehyde and a ketone group (osuloses). Keto acids are known as ulosonic acids. 

The generic term monosaccharide (as opposed to oligosaccharide or polysaccharide) denotes a single unit, without glycosidic connection to other such units. It includes aldoses, dialdoses, aldoketoses, ketoses and diketoses, as well as deoxy sugars and amino sugars, and their derivatives, provided that the parent compound has a (potential) carbonyl gTOup. 

Monosaccharides containing two (potential) aldehydic carbonyl groups are called dialdoses (see 2-Carb-9). 

The parent that includes the functional group most preferred by general principles of organic nomenclature [13,14], If there is a choice, it is made on the basis of the greatest number of occurrences of the most preferred functional group. Thus aldaric acid > uronic acid/ketoaldonic acid/aldonic acid > dialdose > ketoal-dose/aldose > diketose > ketose. 

For the specification of a and (3 in cyclic forms see 2-Carb-6. 2-Carb-9. Dialdoses... 

Systematic names for individual dialdoses are formed from the systematic stem name for the corresponding aldose (see 2-Carb-8.2), but with the ending odialdose instead of ose , and the appropriate configurational prefix (Chart I). A choice between the two possible aldose parent names is made on the basis of 2-Carb-2.2.2. 

Deoxy-3-[(l/Z,2S)-l,2-dihydroxy-3-oxopropyl]-D-gZycer0-D-aZfr0-heptopyranose or 3-deoxy-3-(D-f/jreo-1,2-dihydroxy-3-oxopropyl)-D-g/ycero-D-a/rro-heptopyranose (not the alternative open-chain six-carbon dialdose or eight-carbon aldose, cf. 2)... 

Oxidation of 2 with methyl sulfoxide and boron trifluoride proceeds by conversion of the oxirane ring into an a-hydroxy aldehyde group, just as for simple oxiranes, giving198 the dialdose derivative 66. 

Aldos-2-uk>ses, which have foe ketonic function at C-2, undergo mercaptaladon under the usual conditions, to afford only l,l-(dialkyl dithioacetal) derivatives. The ketone function in these compounds is distinctly unreactive toward thiols in acidic medium, probably as a consequence of electronic and steric effects [42] (Scheme 11). Examples of l,2-bis(dialkyl dithioacetal) derivatives have been prepared by indirect methods [43]. Dialdoses, on the other hand, in which the two carbonyl groups are separated by the sugar backbone, readily undergo mercaptalation at both carbonyl centers to afford bis(dialkyl dithioacetal) derivatives [44]. 

The glycosyl a-amino aldehyde 70 obtained from the dialdose 49 through the nitrone 69 appeared nicely tailored for a rapid conversion to 71. This simply involved the reduction of the formyl group and removal of the hydroxyl and amino protective groups. This approach should be extendible to the synthesis of various aza sugars containing suitable structural modifications. 

R. M. Paton and A. A. Young, The nitrile oxide-isoxazoline route to higher-carbon dialdoses, J. Chem. Soc. Chem. Commun. p. 993 (1994). 

A. Dondoni, G. Fantin, M. Fogagnolo, and A. Medici, Stereospecific homologation of d-xylo and D-galacto dialdoses, Tetrahedron 43 3533 (1987). 

A related reaction of more general applicability occurs with the octos-3,7-diulose derivative 27, which was made from the C-3 epimer of dialdose acetal 4 by treatment with (2-oxopropylidene)triphenylphosphorane in a Wittig chain extension reaction, followed by hydrogenation of the resulting enone and oxidation of the alcohol groups at C-3 and C-7. Cyclilzation to give the crystalline tertiary alcohol 28 in 81% yield is promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing benzene (Scheme 7) [16]. 

Oxygen suppresses the formation of deoxy compounds, and enhances the formation of fragmentation products. As expected from the results obtained with neutral sugars (see Sect. Ill,2b), the most prominent fragment-product here is 2-acetamido-2-deoxy-L-fhreo-tetro-dialdose.37... 

An alternative synthesis468 of L-idonic acid is shown in Scheme 15. On oxidation with periodate, 1,2-O-isopropylidene-a-D-glucofuranose (56) yields the protected dialdose 91. When 91 is treated with hydrogen cyanide, a mixture (92) of the Q-gluco and L-tdo nitriles results, with the D-gluco nitrile preponderating. Hydrolysis affords L-iduronic... 

Methods for the chemical synthesis of glycuronic acids include (i) reduction of the monolactones of aldaric acids, (ii) oxidation of the primary alcoholic group of aldose derivatives, (iii) oxidative degradation procedures, (iv) chain-extension reactions on dialdoses, and (v) epimerization reactions. 

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