Instruments and methods. NMR spectra were recorded on an Avance 400 ( 1 H NMR 400 MHz, C NMR 101 MHz) or a Bruker AMX 500 spectrometer ( 1 H NMR 500 MHz, C NMR 125 MHz) at 293 K. Chemical shifts () are reported in ppm using residual solvent protons ( 1 H NMR: H = 7.26 for CDCl3; C NMR: C = 77.2 for CDCl3) as internal standard. The splitting patterns are designated as follows: s (singlet), d (doublet), dd (doublet of doublet), t (triplet), and m (multiplet). Coupling constants J relate to proton-proton couplings and assignments were made according to the nomenclature numbering scheme. High resolution MALDI mass spectra were performed on a Bruker SolariX using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2propenylidene]malononitrile (DCTB) as matrix. High resolution ESI spectra were performed on a Bruker SolariX using acetonitrile as solvent. The calculated and measured m/z values relate to the monoisotopic masses. GC-MS measurements were performed on a Shimadzu GCMS-QP2010 SE equipped with an Optima 5MS column (30 m x 0.25 mm) from Macherey-Nagel. The samples were ionized by electron impact (EI). GC measurements were performed on a Shimadzu GC-2010 Plus gas chromatograph with hydrogen as carrier gas.