[1] Univ Ioannina, Dept Chem, NMR Ctr, GR-45110 Ioannina, Greece
[2] Univ Tubingen, Inst Organ Chem, D-72076 Tubingen, Germany
[3] Univ Wageningen & Res Ctr, Organ Chem Lab, Nat Prod Chem Grp, NL-6703 HB Wageningen, Netherlands
[4] Univ Wageningen & Res Ctr, Biochem Lab, NL-6703 HA Wageningen, Netherlands
[5] Univ Ioannina, Dept Chem, Sect Organ Chem & Biochem, GR-45110 Ioannina, Greece