G. Englert et al., NMR-STUDIES ON NATURAL L-TRANS-(9'Z,11'Z)-(3R,3'S,5'R,6'R)-PYRRHOXANTHIN, AN ACETYLENIC-C-37-SKELETAL NOR-CAROTENOID BUTENOLIDE, Magnetic resonance in chemistry, 31(10), 1993, pp. 910-915
ll-trans-(9'Z,11'Z)-(3R,3'S,5'R,6'R)-pyrrhoxanthin was isolated from a
natural bloom of dinoflagellates (mainly Ceratium spp.) and submitted
to detailed H-1 NMR and C-13 NMR analysis, including homonuclear COSY
(2D), ROESY (1D and 2D), TOCSY (1D) and H-1-detected one-bond and mul
tiple-bond H-1, C-13 COSY. All chemical shifts and coupling constants
in the H-1 NMR spectrum and all carbons in the C-13 NMR spectrum were
assigned. The result is consistent with the structure, previously dedu
ced, including relative configuration. A recently proposed variant of
the ROESY pulse sequence, called T-ROESY, claimed to suppress undesire
d TOCSY transfer, provided excellent results free of TOCSY artifacts c
aused by coherent magnetization transfer via J coupling pathways indep
endent of the choice of the position of the carrier frequency.