(5R,6S,7R,8R,9S,10R)-5,6-dihydroxy-7,8:9,10-di-O-isopropylidene-7,8,9,10-tetraoxotridecanoic acid tert-butyl ester

(5S,6S,7R,8R,9S,10R)-5,6-dihydroxy-7,8:9,10-di-O-isopropylidene-7,8,9,10-tetraoxotridecanoic acid tert-butyl ester