Regioselective Base-induced Ethereal Bridge Openings of 7-Oxabicyclo[2.2.1]heptane-2,3-dicarboxylic Derivatives; Synthesis of Squalestatin Core Analogues

All articles of this category The Diels-Alder adduct of furfuryl alcohol and maleic anhydride was converted into dimethyl 5- exo ,6- exo -dihydroxy-1-{[tris(isopropyl)silyloxy]methyl}-7-oxabicyclo[2.2.1]heptane-2- exo ,3- exo -dicarboxylate ( 12 ). Regioselective monosilylation of diol 12 gave the 5- O -( tert -butyl)dimethylsilyl ether 18 . Under basic conditions the 7-oxanorbornane system of 18 was isomerized selectively into a 4,5,6-trihydroxy-6-(hydroxymethyl)cyclohex-2-ene-1,2-dicarboxylic derivative that was converted into a doubly-branched hepturonic acid derivative ( 24 ), potential precursor for the preparation of squalestatin core analogues. dioxoheptanoic acid - hepturonic acid - ketoester selective reduction - 7-oxabicyclo[2.2.1]heptane - oxepane - ozonolysis