Configuration of carotenoid epoxides

Synthesis and X‐Ray Structure of (6′RS,8′RS,2E)‐ and (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2′,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ and (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionylidene]acetaldehyde) To check our previous spectroscopic assignments of the structures of trans‐ and cis‐substituted furanoid end groups of carotenoid‐5,8‐epoxides, we now have synthesized the title compounds. An X‐ray structure determination of a single crystal of the trans‐isomer (±)‐‐10A is in agreement with the 1H‐NMR spectroscopic arguments: isomers with Δδ (HC(7), HC(8)) = 0.15–0.22 ppm and J > 1.4 for HC(7) belong to the cis‐series; Δδ in trans‐compounds is < 0.07 ppm, and HC(7) appears as a broad singulett.

Section: Discussionunclassified

“…MS: 236 (IJ, M + ) ,221 (7,8, M +-15), 205 (74, M ' -31),165 (19,8), 149(7,3), 135(lo), 95 (23,7), 59 (41,2), 43 (100). Anal.…”

mentioning

confidence: 99%

(6′RS,8′RS,2E)‐ und (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2y,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ und (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionyloinden]acetaldehyd): Synthese und Röntgenstrukturanalyse

Acemoglu

Prewo

Bieri

et al. 1984

“…Bei der saurekatalysierten Umlagerung von 5,6-Epoxiden bleibt die Konfiguration an C ( 5 ) erhalten [23] [24]. Somit kann auf die Konfiguration der Epoxidfunktion in 1 und 2 geschlossen werden.…”

Section: 'R)-58-epoxy-58-dihydro-fi P-carotin-33'-dia/ (4)) Epiunclassified

Absolute Konfiguration von Antheraxanthin, «cis‐Antheraxantliirt» und der diastereomeren Mutatoxanthine

Märki‐Fischer

Buchecker

Eugster

et al. 1982

Absolute Configuration of Antheraxanthin, ‘cis‐Aritheraxanthin’ and of the Stereoisomeric Mutatdxanthins The assignement of structure 2 to antheraxanthin (all‐E)‐(3 S, 5 R, 6 S, 3′ R)‐5,6‐epoxy‐5,6‐dihydro‐β,β‐carotene‐3,3′‐diol and of 1 to ‘cis‐antheraxanthin’ (9Z)‐(3 S, 5 R, 6 S, 3′ R)‐5,6‐epoxy‐5,6‐dihydro‐β,β‐carotene‐3,3′‐diol is based on chemical correlation with (3 R, 3′ R)‐zeaxanthin and extensive 1H‐NMR. measurements at 400 MHz. ‘Semisynthetic antheraxanthin’ ( = ‘antheraxanthin B’) has structure 6. For the first time the so‐called ‘mutatoxanthin’, a known rearrangement product of either 1 or 2, has been separated into pure and crystalline C(8)‐epimers (epimer A of m.p. 213° and epimer B of m.p. 159°). Their structures were assigned by spectroscopical and chiroptical correlations with flavoxanthin and chrysanthemaxanthin. Epimer A is (3 S, 5 R, 8 S, 3′ R)‐5,8‐epoxy‐5,8‐dihydro‐β,β‐carotene‐3,3′‐diol (4; = (8 S)mutatoxanthin) and epimer B is (3 S, 5 R, 8 R, 3′ R)‐5,8‐epoxy‐5,8‐dihydro‐β,β‐carotene‐3,3′‐diol (3; = (8 R)‐mutatoxanthin). The carotenoids 1–4 have a widespread occurrence in plants. We also describe their separation by HPLC. techniques. CD. spectra measured at room temperature and at − 180° are presented for 1–4 and 6. Antheraxanthin (2) and (9Z)‐antheraxanthin (1) exhibit a typical conservative CD. The CD. Spectra also allow an easy differentiation of 6 from its epimer 2. The isomeric (9Z)‐antheraxanthin (1) shows the expected inversion of the CD. curve in the UV. range. The CD. spectra of the epimeric mutatoxanthins 3 and 4 (β end group) are dissimilar to those of flavoxanthin/chrysanthemaxanthin (ε end group). They allow an easy differentiation of the C (8)‐epimers.

“…Unsere Schlussfolgerungen stimmen nicht in allen Teilen mit den aus 'H-NMR.-Spektren gezogenen Schlussen von Goodfellow et al in ihrer bereits erwahnten Mitteilung [4] uberein. Dies betrifft u.a.…”

Section: Isomerunclassified

Über die Carotinoide Flavoxanthin und Chrysanthemaxanthin: ¹H‐NMR.‐, ¹³C‐NMR.‐ und Massen‐Spektren und absolute Konfiguration. (Kritische Überprüfung veröffentlichter chemischer und physikalischer Daten)

Cadosch

Vögeli

Rüedi

et al. 1978

On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: 1H‐NMR., 13C‐NMR. and Mass Spectra, Absolute Configuration, Survey of Published Data Very pure flavoxanthin (1) and chrysanthemaxanthin (2) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa. Chemical degradation of 1 and 2 to (−)‐loliolide (5) coupled with NMR. evidence (ASIS, spin‐decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2. Thus (+)‐flavoxanthin is (3S,5R,8R, 3′R,6′R)‐5, 8‐epoxy‐5, 8‐dihydro‐β, ε‐carotene‐3, 3′‐diol and (+)‐chrysanthemaxanthin its C(8)‐epimer.