Tarapacol 15-Acetate, a New Diterpenoid from Grindelia tarapacana Phil.

In the title compound, 15-acetoxy-14(S)-hydroxy-13-epi-manoyl oxide {IUPAC systematic name: 2-(dodecahydro-3,4a,7,7,10a-pentamethyl-1H-naphtho[2,1-b]pyran-3-yl)-2-hydroxyethyl acetate}, C₂₂H₃₈N₄, rings A and B have chair conformations. Ring C adopts a boat conformation with the 16-methyl group in an axial position and the bulky glycol monoacetate group in an equatorial position. Ring systems A/B and B/C (conventional IUPAC labdane diterpenoid nomenclature) are trans fused about the C(5)-C(10) and C(8)-C(9) bonds, respectively. The present study establishes the relative stereochemistry at the C(14) position.

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