1D and 2D NMR study of some allenic carotenoids of the fucoxanthin series

✍ Scribed by Gerhard Englert; Terje Bjørnland; Synnøve Liaaen-Jensen

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 943 KB
• Volume: 28
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260280610

✦ Synopsis

Abstract

The allenic carotenoid all‐trans‐(3__S__,5__R__,6__S__,3′S,5′R,6′R)‐19′‐butanoyloxyfucoxanthin, isolated from the marine chrysophyte Pelagococcus subviridis, and its 9′‐cis isomer, obtained in 45% yield on iodine‐catalysed stereomutation, were submitted to a detailed ^1^H and ^13^C NMR analysis. For comparison, all‐trans‐fucoxanthin [(3__S__,5__R__,6__S__3′S,5′R,6′R)‐5,6‐epoxy‐3,3′,5′‐trihydroxy‐6′,7′‐didehydro‐5,6,7,8,5′,6′‐hexahydro‐β,β‐caroten‐8 ‐one‐3′‐acetate] was included in the study. The complete assignments of the 400 MHz ^1^H NMR spectra and of the 100.6 MHz ^13^C NMR spectra, including the stereochemistry, were possible by application of two‐dimensional ^1^H,^1^H chemical shift correlated spectroscopy (2D COSY), 1D and 2D total correlation spectroscopy (TOCSY, HOHAHA), rotating‐frame nuclear Overhauser spectroscopy (ROESY, CAMELSPIN) and ^1^H‐detected one‐bond (with and without ^13^C decoupling) and multiple‐bond ^1^H, ^13^C‐correlated 2D spectroscopy. The 9′‐trans to 9′‐cis stereomutation was unequivocally proved for 19′‐butanoyloxyfucoxanthin, mainly by 1D and 2D ROESY experiments; this is in contrast to a previously claimed 6′R → 6′S stereomutation in related allenic carotenoids.