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This paper reports the development of a silver-catalyzed 6-endo-dig cyclisation of 5-alkoxy-1,5-enynes enabling benzannulation of (-)-menthone with construction of the calamenene skeleton as a single isomer. The total syntheses of (7S,10R)-2,15-dihydroxycalamenene (6 steps, 39.6%), (7S,10R)-2-hydroxy-15-calamenenal (7 steps, 10.7%) and (7S,10R)-2-Hydroxy-15-calamenenoic acid (9 steps, 33.6%) were achieved from (-)-menthone via a common intermediate. Analysis of the spectroscopic data as well as the specific rotations allowed for confirmation of the stereochemistry at C1 and C4 of the natural compounds isolated from Tarenna madagascariensis as (7R,10S)-2,15-dihydroxycalamenene and (7R,10S)-2-hydroxy-15-calamenenal, and the carboxylic acid isolated from Alpinia oxymitra was confirmed as (7S,10R)-2-hydroxy-15-calamenenoic acid. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]