18-Nor-Kaurane Type Diterpenoids from the Fruits of Atemoya

A phytochemical investigation on the flesh fruits of atemoya led to the isolation of seven new kaurane type diterpenoids, (4S*,5S*,8S*,9R*,10S*,13R*,16R*)-16-hydro-18-nor-kauran-4,17-diol (1), (4S*,5S*,8S*,9R*,10S*,13R*,16S*)-18-nor-kauran-4,16,17-triol (2), (4S*,5S*,8S*,9R*,10S*,13R*,16S*)-17-acetoxy-18-nor-kauran-4,16-diol (3), (4S*,5S*,8S*,9R*,10S*,13R*,16R*)-18-nor-kauran-4,16,17-triol (4), (4S*,5S*,8S*,9R*,10S*,13R*,16S*)-17-acetoxy-16-hydro-18-nor-kauran-4-ol (5), (4R*,5S*,8S*,9R*,10S*,13R*,16S*)-16,17-dihydroxy-19-nor-kauran-4-hydroperoxide (6), and (4R*,5S*,8S*,9R*,10S*,13R*,16S*)-kauran-16,19-diol (7) along with 26 known ent-kaurane compounds. Their structures are determined on the basis of spectroscopic data and optical rotation. Compounds 1-5 were new 18-nor-kauran-4-ol type diterpenoids, which are very rarely obtained from natural sources.