Lewis acid-catalyzed, hetero Diels-Alderreaction of (E)-1-methoxy-3-trimethylsilyloxy-1,3-butadiene with 6-benzoyloxymethyl-2,4-dibenzyloxy benzaldehyde afforded 2-(6-benzoyloxymethyl-2,4-dibenzyloxyphenyl)-2,3-dihydro-4H- pyran-4-one. This was converted into a derivative of papulacandin D by a stereo-specific, spiroacetalization of a C-1 methoxylated aryl glycoside, [3,5-dibenzoyloxy-(methyl 3-O-acetyl-4