Silver-catalyzed benzannulation, part 2: Total synthesis of (1R,4S,11S)-8,19-dihydroxyserrulat-14-ene and (1R,4S,11S)-8-hydroxyserrulat-14-en-19-oic acid

This paper reports the total synthesis of the serrulatane natural products (1R,4S,11S)-8,19-dihydroxyserrulat-14-ene (5.0% yield) and (1R,4S,11S)-8-hydroxyserrulat-14-en-19-oic acid (3.8% yield) via a silver-catalyzed 6-endo-dig benzannulation of an (−)-isopulegol derived ene-yne-ol in 17 steps. Analysis of the spectroscopic data as well as the specific rotations allowed for the confirmation of the stereochemistry at C1, C4 and C11 as (1R,4S,11S) for both natural products 8,19-dihydroxyserrulat-14-ene and 8-hydroxyserrulat-14-en-19-oic acid that were reported from the Australian desert plant, Eremophila neglecta.