Synthesis of sedoheptulose from 2-C-(hydroxymethyl)-D-allose by molybdic acid-catalysed carbon-skeleton rearrangement

A new branched-chain aldose, 2-C-(hydroxymethyl)-D-allose (3), was obtained by a base-catalysed addition of 2,3:5,6-di-O-isopropylidene-beta-D-allofur anose to formaldehyde followed by acid hydrolysis of the aldol product. On treatment with a catalytic amount of molybdic acid at 90 degrees C, 3 affor ded its equilibrium mixture with sedoheptulose tautomeric and anhydro forms in the ratio 12:1. Sedoheptulose in its 2,7-anhydro form, 2,7-anhydro-beta -D-altuo-heptulopyranose, was obtained from this mixture by treatment with 0.5 M H2SO4 and crystallisation (overall 63% yield). (C) 1999 Elsevier Scie nce Ltd. All rights reserved.