Oxidation—continued with selenium dioxide

As previously noted, the high temperature of the combustion process causes the nitrogen and oxygen in the air to react to produce nitrogen oxides. The non-carbon (elements) impurities in the fuels react to form oxides sulfur dioxide is the primary hazardous product, but others such as selenium dioxide and arsenic trioxide are also produced. Mercury is released as vapor. When vented from the combustion zones this complex mixture of compounds blends with the air. Under the influence of sunlight, it continues to react to produce the complex product, smog. "... 

Sideritis (Labiatae) species have continued to attract attention as a source of diterpenoids. n/-lljS,18-Dihydroxykaur-15-ene (49) was obtained from 5. chamaedryfolia and the known diterpenoids foliol (enr-3/8,7a,18-trihydroxy-kaur-16-ene) and its 3- and 18-monoacetates (sidol and linearol) were detected in S. arborescens ° and along with their A -isomers and 18-hydroxykaur-16-ene (candol B) in S. flavovirens. A similar group of hydroxykaurenes was found in S.funkiana whilst enr-18-acetoxy-3jS,6a,7a-trihydroxykaur-15-ene (funkiol) and the isomeric 3-acetate (sidofunkiol) were amongst the minor constituents. The selective allylic oxidation of the kaur-16-enes at C-15 by hydrogen peroxide and selenium dioxide is facilitated by the presence of a 7-hydroxy-group. 

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