Formaldehyde aldol products rearrangement

The synthetic design based on the molybdic acid catalyzed carbon-skeleton rearrangement of the branched chain aldose as applied above to prepare sedo-heptulose has also been exploited for the synthesis of D-glycero-D-ido-octu ose [63]. The necessary branched-chain aldose 45,2-C-(hydroxymethyl)-D-g/ycero-D-gw/o-heptose,was obtained by the potassium carbonate catalyzed aldolization of the D-glycero-D-gulo-heiptose derivative 43 [64], which has an anchored configuration at C-2,by 2,3-0-isopropylidenation with formaldehyde and by subsequent deprotection of the aldolization product 44. 

The formose reaction in detail, however, consists of a series of reactions primary self-addition of formaldehyde followed by aldol reaction of products with each odier and with formaldehyde. Cannizzaro and cross-Cannizzaro reactions occur, as well as Lobry de Bruyn-Alberda van Ekenstein rearrangements. Product decomposition (for example, to chromophores) occurs if the reaction conditions are unduly severe. The monosaccharides formed are all dl (racemic), with no optical rotatory... 

---