The present invention relates to bi- and tricyclic compounds of the general formula (I) (I) wherein the dashed lines independently of each other represent a single or a double bond, X represents a group of the formulae X.sub.1 to X.sub.3 wherein the asterisk denotes the point of attachment to the rest of the molecule, R.sup.1a and R.sup.1b, independently of each other, are selected from hydrogen or methyl, or R.sup.1a together with R.sup.1b form a methylene or ethylene group, R.sup.2, R.sup.3a, R.sup.3b, R.sup.4, R.sup.5a and R.sup.5b, independently of each other, are selected from hydrogen or methyl, R.sup.6 is selected from hydrogen, methyl or ethyl, and R.sup.7 is methyl or ethyl, to a method of preparing said compounds, to the use of a bi- or tricyclic compounds or of mixtures of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use of a bi- or tricyclic compound for modifying the scent character of a fragranced composition; to an aroma chemical composition containing a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition, comprising incorporating a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof into said composition. ##STR00001##

The present invention relates to bi- and tricyclic compounds of the general formula (I) (I) wherein the dashed lines independently of each other represent a single or a double bond, X represents a group of the formulae X.sub.1 to X.sub.3 wherein the asterisk denotes the point of attachment to the rest of the molecule, R.sup.1a and R.sup.1b, independently of each other, are selected from hydrogen or methyl, or R.sup.1a together with R.sup.1b form a methylene or ethylene group, R.sup.2, R.sup.3a, R.sup.3b, R.sup.4, R.sup.5a and R.sup.5b, independently of each other, are selected from hydrogen or methyl, R.sup.6 is selected from hydrogen, methyl or ethyl, and R.sup.7 is methyl or ethyl, to a method of preparing said compounds, to the use of a bi- or tricyclic compounds or of mixtures of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use of a bi- or tricyclic compound for modifying the scent character of a fragranced composition; to an aroma chemical composition containing a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition, comprising incorporating a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof into said composition. ##STR00001##

A method to generate dense, multi-cyclic diamondoid fuels from bio-derived sesquiterpenes. This process can be conducted with both heterogeneous and homogenous catalysts and produces the targeted isomers in high yield. The resulting multi-cyclic structures impart significantly higher densities and volumetric net heats of combustion while maintaining low viscosities which allow for use at low temperature/high altitude. Moreover, bio-derived sesquiterpenes can be produced from renewable biomass sources. Use of these fuels will decrease Navy dependence on fossil fuels and will also reduce net carbon emissions.

A method to generate dense, multi-cyclic diamondoid fuels from bio-derived sesquiterpenes. This process can be conducted with both heterogeneous and homogenous catalysts and produces the targeted isomers in high yield. The resulting multi-cyclic structures impart significantly higher densities and volumetric net heats of combustion while maintaining low viscosities which allow for use at low temperature/high altitude. Moreover, bio-derived sesquiterpenes can be produced from renewable biomass sources. Use of these fuels will decrease Navy dependence on fossil fuels and will also reduce net carbon emissions.