Enantioselective formal total syntheses of Clavukerin A and isoclavukerin A via a ring-closing metathesis reaction

Enantioselective formal total syntheses of the marine trisnorsesquiterpenes clavukerin A and isoclavukerin A, starting from (R)-limonene employing an RCM reaction as the key step, are described.

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1-[(5S)-5-Isopropenyl-2-methylcyclopent-1-en-1-yl]pent-4-en-1-oneC14H20O[α]D24=+101.0 (c 4.6, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (5′S)

(7S)-6,10-Dimethylbicyclo[5.3.0]deca-1(10),5-dien-2-oneC12H16O[α]D25=-98.9 (c 2.5, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (7S)

(1R,7S,10S)-6,10-Dimethyl-11-oxatricyclo[5.4.0.01,10]undec-5-en-2-oneC12H16O2[α]D27=-82.1 (c 1.2, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (1R,7S,10S)

(1S,7S,10R)-6,10-Dimethyl-11-oxatricyclo[5.4.0.01,10]undec-5-en-2-oneC12H16O2[α]D24=-191.6 (c 2.5, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (1R,3S)

(1R,6S,7S,10S)-6,10-Dimethyl-11-oxatricyclo[5.4.0.01,10]-undecan-2-oneC12H18O2[α]D24=-34.3 (c 1.4, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (1R,6S,7S,10S)

(1S,6S,7S,10R)-6,10-Dimethyl-11-oxatricyclo[5.4.0.01,10]-undecan-2-oneC12H18O2[α]D26=-108.5 (c 5.7, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (1S,6S,7S,10R)

(1S,6R,7S,10R)-6,10-Dimethyl-11-oxatricyclo[5.4.0.01,10]-undecan-2-oneC12H18O2[α]D26=-80.6 (c 1.8, CHCl3)Source of chirality: (R)-limoneneAbsolute configuration: (1S,6R,7S,10R)