A Chemical Study of Burley Tobacco Flavour (Nicotiana tabacum L.). III. Structure Determination and Synthesis of 5-(4-Methyl-2-furyl)-6-methylheptan-2-one (“Solanofuran”) and of 3,4,7-Trimethyl-1,6- dioxa-spiro[4.5]dec-3-en-2-one (“Spiroxabovolide”), Two New Flavour Components of Burley Tobacco

Two novel constituents of Burley tobacco condensate were shown to be 5-(4-methyl-2-furyl)-6-methylheptan-2-one (solanofuran, 4 ) and 3,4,7-trimethyl-1,6-dioxa-spiro[4.5]-dec-3-en-2-one (spiroxabovolide, 6 ). These structures were deduced from spectral data and confirmed by synthesis. Solanofuran ( 4 ) was prepared via the dye-sensitized photo-oxygenation of solanone ( 1 ). This type of reaction involving the uncommon ‘diene-addition’ of ¹O₂ to a conjugated acyclic diene system was thus applied for the first time to the synthesis of a terpenoid furan, a route that might have some biogenetic significance. Both solanofuran ( 4 ) and spiroxabovolide ( 6 ) display interesting organoleptic properties. Identification of these compounds increases to 210 the total number of Burley tobacco flavour constituents so far characterized in this laboratory.