Conformational Analysis,Thermal Rearrangement,and EI‐MS Fragmentation Mechanism of (1(10)E,4E,6S,7R)‐Germacradien‐6‐ol by 13C‐Labeling Experiments

An uncharacterized terpene cyclase from Streptomyces pratensis was identified as (+)‐(1(10)E,4E,6S,7R)‐germacradien‐6‐ol synthase. The enzyme product exists as two interconvertible conformers, resulting in complex NMR spectra. For the complete assignment of NMR data, all fifteen (¹³C₁)FPP isotopomers (FPP=farnesyl diphosphate) and (¹³C₁₅)FPP were synthesized and enzymatically converted. The products were analyzed using various NMR techniques, including ¹³C, ¹³C COSY experiments. The (¹³C)FPP isotopomers were also used to investigate the thermal rearrangement and EI fragmentation of the enzyme product.     

1H‐ und 13C‐NMR‐Spektroskopie

The present state of the routine 1D ¹H‐ and ¹³C‐NMR spectroscopy is reported. After a short introduction into the basic theory the current spectrometer and software systems are discussed. Using an example from natural product chemistry the procedures during the analysis of the NMR spectra are explained.     

Stereoselective Total Synthesis of Oxylipins: (6S,7E,9R,10S)‐6,9,10‐Trihydroxyoctadec‐7‐enoic Acid and (6Z,8R,9R,10S)‐8,9,10‐Trihydroxyoctadec‐6‐enoic Acid

The stereoselective total syntheses of oxylipins 1b and 1c are described starting from readily accessible natural sugars via the Grubbs cross‐metathesis, Wittig olefination, and Zn‐mediated reductive elimination as key steps.