An approach to the bicyclic core of the zaragozic acids via the aldol reaction between methyl (alpha-D-xylofuranoside)uronate and D-(R)-glyceraldehyde acetonide

The aldol reaction between methyl (methyl-3-O-benzyl-2-O-methoxymethyl-alph a-D-xylofurano-side)uronate and D-(R)-glyceraldehyde acetonide, promoted by cerium(III) chloride, led to three diastereoisomers in good yield and high level of stereoselectivity at the newly created quaternary center of the f uranoside. Under acidic conditions, the aldol derivatives undergo transketa lization to afford different bicyclic ketal isomers. This reaction was used as the key step in the synthesis of a functionalized bicyclic core of the zaragozic acids. (C) 1999 Elsevier Science Ltd. All rights reserved.