Dialdoses reactions

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]. 

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. 

The aldehydes at C-6 of dialdoses have also been used as dienophiles in hetero-Diels-Alder reactions.400... 

Reaction of several dialdose derivatives, for example 197, with furan or 2-methylfuran gave, in the presence of chloroacetic acid, condensation products with high stereoselectivity. The (S) configuration was assigned to the major diastereoisomer 198.401 The thiazole adduct (199) obtained from aldehyde 197 and 2-trimethylsilylthiazole can be converted to the 6-epimer (200) by an oxidation-reduction sequence (Scheme 20).402... 

A direct method for two-carbon sugar homologation of dialdoses leads to sugar /1-ketoesters. Thus, reaction of dialdose derivative 203 with ethyl diazoacetate in the presence of BF3 etherate alfords the /1-ketoester 204.404... 

Some choice between the two possible mechanisms can be made by studying the periodate oxidation of pinitol,66 sequoyitol,78 and profo-quercitol.79 If a methylene (deoxy) or an O-methyl group should occur at C3 or C4 of the hexodialdose, the rapid periodate oxidation of the cyclic form XXXVI would end after the consumption of only 2 or 3 moles of periodate per mole, respectively, and would then continue only at the very slow rate governed by the hydrolysis of the formate ester. The above compounds give hexo-dialdoses of this nature, but they rapidly consume some four moles of periodate per mole. This indicates that the major path of the reaction is not the one by way of cyclic intermediates this conclusion is probably valid for the inositols, too. 

With the objective of synthetic utilization of a,/3-unsaturated dialdoses, the Wittig reaction with certain compounds of this series... 

Application of the ring-closing olefin metathesis reaction (RCM) for the preparation of car-bocyclic rings from the appropriately functionalized sugars is now well documented [81]. Recently it was applied for the synthesis of compound 122, which can be regarded as a (n,m)-anhydrosugar [81]. The intermediate diolefin 121 was prepared in a few standard steps from the corresponding dialdose 120 (O Fig. 28) [82]. 

The reactions of allyltrialkylstannanes with dialdose derivatives proceed similarly, with a high di-astereofacial selectivity in 5.0 M LPDE via chelation-controlled catalysis by the lithium ion. For example, the galactose derivative (4) (1.0 M in ether) reacts with 1.5 equivalents of allyltri-n-butyltin in 5.0 M LPDE, giving rise after 1 h to 96% yield of 5 and 6 in a ratio 25 1, respectively (Scheme 6.3.3). Exposure of (4) to allyltrimethyltin in 5.0 M LPDE proceeded with a high diastereofacial selectivity >25 1. In contrast, treatment of (4) with allyltrimethyltin in 2.0 M LPDE at ambient temperature proceeded with reduced diastereofacial selectivity, giving rise to a 12 1 ratio of (5) and (6), respectively, in only 66% yield. 

The Weerman degradation was employed in one of the first preparations of dialdoses, namely of n-f/ireo-tetrodialdose, using the diamide of D-glucaric acid as starting material. An inosose has been degraded to a pentodialdose by way of its disulfone and the Nef reaction, transformation of a 6-deoxy-... 

Clauson-Kaas and Fakstorp prepared the dialdose, isolated as the bis(phenylhydrazone), by the hydroxylation of furan. This reaction was performed with hydrogen peroxide/osmium tetraoxide in aqueous methanol and was expected, assuming 1,4-addition of the hydroxyl groups, to yield... 

MacDonald and Fischer prepared D- fluco-hexodialdose (27) by two different methods. By use of the Nef reaction, 6-deoxy-l,2-0-isopropyli-dene-6-nitro-n-glucose (26) was converted into the dialdose (27), which was isolated from the aqueous solution as its insoluble, crystalline bis-(diethyl dithioacetal) (in 48% yield, after recrystallization). It is of interest to note that the starting material (26) is one of the two isomeric 6-deoxy-6-nitro sugars which Grosheintz and Fischer prepared from 1,2-0-iso-propylidene-a-D-x2/lo-pentodialdo-l, 4-furanose (7). Thus, the synthesis discussed here is an ascent from a pentodialdose to a hexodialdose. 

A general method for the synthesis of dialdoses and nucleoside 5 -aldehydes has been described, and their asymmetric reaction with nucleophiles discussed. The reversible interconversion of GDP-D-mannose and -L-galactose which is brought about by a Chorella enzyme system was proposed to occur as shown in Scheme 2 following the observation that tritium incorporation from the solvent occurred equally at C-3 and C-5. Epimerizations at positions a to the carbonyl groups can also be photoinduced, and compound (1) has now been isolated in... 

A study on the Knoevenagel reaction of some aldehydo dialdose derivatives with pentane-2,4-dione revealed that acetyl transfer... 

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