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The biomimetic synthesis of sacculatane-type epimeric compounds 14a and 14b is reported. The key synthetic step is the low-temperature superacidic cyclization of (all-E)-ω-acetoxygeranylgeraniol 12 obtained in nine steps from geranyllinalool (13). The 19-acetoxysacculata-7,17-dien-11-ol (14a) could be an important and convenient starting compound for the synthesis of other sacculatane diterpenoids. [ABSTRACT FROM AUTHOR]

Methyl (2Z,6Z,10E,14E)- (3) and methyl (2E,6Z,10E,14E)-geranylfarnesoate (4) were prepared, and then individually cyclized in the presence of the superacid FSO3H. In the case of substrate 3, the scalaranic ester 9 (26%) and the cheilanthanic ester 10 (39%) were isolated. Under the same conditions, substrate 4 afforded a mixture of the corresponding stereoisomers 11 (25%) and 12 (63%). The observed product selectivity supports that the internal, (6Z)-configured C=C bond in these and other biologically relevant substrates plays an essential role in the cyclization process. [ABSTRACT FROM AUTHOR]