title: Amoenolide K and amoenolide K 19-acetate, two grindelane peroxides from Amphiachyris amoena. Isolation, structure determination, and preparation of amoenolide K from amoenolide A by photochemical oxygenation.
abstract: Two new 9,13-diepoxy labdane diterpenes, amoenolide K [1] and its 19-acetate [2], were isolated from the aerial parts of the composite Amphiachyris amoena and their structures were established by spectral methods, especially high-field nmr spectroscopy. Amoenolide K [1] was prepared from amoenolide A [3] by singlet oxygen addition via the ene reaction. A study was made of the ene reaction products with amoenolide K triacetate [5] which showed them to arise from stereospecific oxygen addition to the 8,9-double bond, with the exception of the sterically hindered beta-side at C-9, for which no products were isolated.
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification; D004224:Diterpenes / Q000737:chemistry / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009284:Naphthols / Q000737:chemistry / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry / Q000302:isolation & purification; D010777:Photochemistry; D010944:Plants / Q000737:chemistry*; D013141:Spiro Compounds / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D004224:Diterpenes; D009284:Naphthols; D010545:Peroxides; D013141:Spiro Compounds; C089561:amoenolide A; C096946:amoenolide K; C096947:amoenolide K 19-acetate; D015107:4-Butyrolactone