Heptonic acids 7- amino-7-deoxy-, derivatives, synthesis

An elegant total synthesis of a semi-protected form of lincosamine has been realized by Marshall and Beaudoin [319]. Destomic acid (6-amino-6-deoxy-L- fycero-D- a/acto-heptonic acid) has been derived in a similar way from a L-serinal derivative via hetero-Diels-Alder addition to l-ethoxy-3-[(trimethylsilyl)oxy]-4-benzyloxy-l,3-butadiene. A similar method has been applied also to prepare a semi-protected form of anhydrogalantinic acid, a component of the antibiotic galantin I [351]. 

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-... 

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