Jürgen Schnaubelt

Studies on the Synthesis of Natural Products with Bicyclo[4.4.0]decene Skeleton: Synthesis and Uncatalysed Intramolecular Diels–Alder Reactions of the Decatrienone Substrates

Starting from enones 7 and 8 siloxydienes 9 and 12 were synthesized. Cyclopropanation and subsequent alkylation with sorbyl bromide provided tetrasubstituted siloxycyclopropanes 15 and 16 in good overall efficiency. Their ring cleavage with fluoride reagents gave 1,7,9-decatrienones 5 and 17; the latter was converted into the protected compound 6. The thermal intramolecular Diels–Alder reactions of 5 and 6 were compared with those of related trienones 3 and 4. Octalones 1, 2, 21, and 22 were formed as mixtures of three or four diastereomers. Thus, for the stereoselective construction of natural products such as α-eudesmol or dihydromevinolin alternative reaction conditions for the cycloaddition step have to be developed.

Crystal structure of trimethyl 3-methyl-4-oxo-(E)-8-cyclodecene-1,1,6-tricarboxylate, C17H24O7

C17H24O7, triclinic, P I ( N o . 2) , a = 7 . 8 5 7 4 ( 6 ) Ä , b = 14 .791(1) Ä , c = 16 .874(2) Ä, α = 107.160(5)°, β = 99 .995(5)° , γ = 9 7 . 5 1 2 ( 5 ) ° , V= 1810 .6 Ä 3 , Z = 4 , R^F) = 0 .049 , RJF) = 0 .095 , Τ = 2 9 8 Κ.