Identification and synthesis of volatiles released by the myxobacterium Chondromyces crocatus

Cultures of the myxobacterium Chondromyces crocatus on agar plates were analysed by closed-loop-stripping analysis or solid phase micro extraction. The odour profiles consist mainly of pyrazines, sesquiterpenoids and some aromatic compounds, summing up to more than 50 components. Several new pyrazines as 2-(1-hydroxy-1-methylethyl)-3-methoxypyrazine (9), 2-(1-hydroxy-1-methylpropyl)-3-methoxypyrazine (10), and 2-(1-hydroxy-2-methylpropyl)-3-methoxypyrazine (11) were identified besides several known pyrazines. A major pyrazine occurring in most samples was 2,5-bis-(1-methylethyl)pyrazine (3). While the well known sesquiterpenoid geosmin (1) was present in low amounts, the related compound (1(10)E,5E)-germacradien-11-ol (21) was identified in most samples in larger quantities. Other prominent sesquiterpenoids not reported before from microorganisms were (6S,10S)-6,10-dimethylbicyclo4.4.0]dec-1-en-3-one (16), which was accompanied by smaller amounts of several derivatives. The biosynthesis of these compounds is discussed in relation to the recently proposed biosynthetic pathways to 1 and 21.