Aldonic acids branched-chain

This section deals with acids, that are formally modified aldonic acids, such as keto, deoxy, and branched-chain acids (including the so-called saccharinic acids). The aminoaldonic acids, which are oxidation products of amino sugars, and, in particular, the important nonulosaminic acids (neuraminic acids) and muramic acid, are not discussed here. The formation of saccharinic acids by the treatment of sugars with alkali, and the mechanisms involved, are likewise outside the scope of this chapter. 

The branched-chain aldonic acid derivative (1) has been shown to be a component of avilamycin by isolation of the product (2) of mild methanolysis and acetylation the latter compound was structurally characterized by X-ray analysis. ... 

Further examples have been reported of the synthesis of aldonic acids by carbon-carbon bond-forming reactions. 2,3 4,5-Di-0-isopropylidene-D-arabinose (3) with methyl acetoacetate gave the Knoevenagel product (4), which is a branched-chain, unsaturated heptonic acid derivative. This rearranged on treatment with trifluoroacetic acid to afford the spiro-product (5) (Scheme 1). This same compound was obtainable from the 2,5-anhydroaldose derivative (6) by similar treatment. The synthesis of destomic acid, 6-amino-6-deoxy-L- /ycew-... 

Sugars Unusual sugars (amino, deoxy and methyl sugars, and sugars with branched chains). Reduction products (sugar alcohols, cyclitols, streptidine). Oxidation products (uronic acids, aldonic acids, sugar dicarboxylic acids). 

The 4-ulose (21) underwent an,ticipated stereoselective reduction with L-selectride to yield the axial alcohol (methyl a-virenoside). The branched-chain aldonic acid (22), related to orthosomycin... 

Branched-chain aldonic acids have received attention (see also saccharinic acids). The synthesis of the L-ldonate and D-galactonate derivatives (6) and (7) as shown in Schemes 2 and 2b served to confirm the structures of the branched-chain 2,3-0-... 

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