¹H‐NMR.‐, ¹³C‐NMR.‐, UV.‐ und CD.‐Daten von synthetischem (3S, 3′S)‐Astaxanthin, seinem 15‐cis‐Isomeren und einigen analogen Verbindungen

Abstract

Herrn Professor Dr. Walter Bogurh zum 60. Geburtstag gewidmet (10.111. 77) lH-NMR., 13C-NMR., UV. and CD. spectral data of synthetic (3S, 3's)-astaxanthin, its 15-cis isomer, and some related compounds Summary 1H-NMR., 13C-NMR., UV. and CD. spectra are reported for synthetic (3 S, 3's)-astaxanthin (l), its 15-cis isomer (2), its diacetate (3), and the 15,15'-didehydro compound (5). These data prove the identity of the synthetic and the naturally occuring compound 1. A full interpretation of the lH-and 13C-NMR. spectra is given and confirms the configuration of all the double bonds. The conformation of the cyclohexene end group of all the compaunds is shown to be identical. The signs of the different CD. maxima of 15-cis-astaxanthin are found to be opposite to those of the all-trans compound.Einleitung. - Obwohl das Vorkommen von Astaxanthin sehr oft in der Literatur erwahnt wird, geschieht dessen Nachweis meist nur durch UV.-und Massen-Spektroskopie. Da haufig freies Astaxanthin und dessen Mono-und Di-ester nebeneinander anzutreffen sind, erfolgt deren gemeinsamer Nachweis in vielen Fallen spektroskopisch sogar erst

Conformation and Optical Activity of all‐trans, mono‐cis, and di‐cis Carotenoids: Temperature Dependent Circular Dichroism

“…This rule has been verified in the present study for trans, 9,9'-di-cis and 15-mono-cis-zeaxanthin and for 9 and 13-cis-zeaxanthin by Hertzberg et al [4]; for trans and 15-mono-cis astaxanthin [5]; for the trans, 9,9'-di-cis and %mono-cis-isomers of 7,8,7', 8'-tetradehydroastaxanthin diacetate (this study); for trans and 9-cis-diatoxanthin (7,s-didehydrozeaxanthin) [4]; for trans and 9-mono-cis-didehydroastaxanthin (this work). The last two compounds and the diatoxanthins possess two dissimilar optically active halves, whereas all the other compounds have two identical optically active rings.…”

“…spectrum of all-trans-astaxanthin in the region 200-400 nm exhibits a CD. spectrum of opposite sign to the 15-cis isorner [ 5 ] . Figures 7 and 8 show the temperature dependent CD.…”

“…The CD. spectra of (3S, 3's)-astaxanthin and the mono-15-cis-isomer are almost perfect mirror images [5]. The CD.…”

“…However, optical antipodes have been used to establish the reliability of the signals reported here. In an earlier paper [ 5 ] , we had only one of the antipodes available. In spite of many precautions, the CD.…”

“…The NMR. spectrum of astaxanthin shows clearly that HO-C (3) occupies the equatorial position thereby preventing the ring from flipping from one half-chair to the other [ 5 ] . A similar result for zeaxanthin has been obtained with 13C-NMR.…”