Synthesis of bis-tetrahydrofuran subunit of (−)-neopallavicinin

The stereospecific Pd/Cu-catalysed oxycarbonylation of syn/anti-hex-5-ene-2,4-diols 7/8 was used as a key step in the synthesis of bicyclic lactones 5 and 6. Eventually, the major intermediate 5 was transformed to the bis-tetrahydrofuran subunit of naturally occurring diterpenoid (−)-neopallavicinin 2. The target compound 3E was thus prepared in 7.5% overall yield over eight steps starting from commercially available (R)-methyl-3-hydroxybutanoate 9.