(+)-Germacrene A, an important intermediate in sesquiterpene biosynthesis, was isolated in pure form from a genetically engineered yeast and was characterized by chromatographic properties (TLC, GC), MS, optical rotation, UV, IR, 1H NMR, and 13C NMR data. Variable- temperature 500MHz 1H NMR spectra in CDCl3 showed that this flexible cyclodecadiene ring exists as three NMR-distinguishable conformational isomers in a ratio of about 5: 3: 2 ...
