C₄₅‐ und C₅₀‐Carotinoide. 5. Mitteilung

Abstract

The synthesis of the optically active C,,-building block (R)-16 and of the optically active Cso-carotenoid C.p. 173 (1) starting from (-)-b-pinene is reported.Einleitung. -Aus Corynebacterium poinsettiae wurden vor einiger Zeit die beiden Zyclischen C,,-Carotinoide C.p. 450 und C.p. 473 isoliert [2] [3]. Neuere Untersuchungen :4-6] zeigten, dass dem C.p. 450 die Struktur von (2R,2'R)-2,2'-Bis(4-hydroxy-3-methylbut-2-enyl)-P,P-carotin und dem C.p. 473 (1) diejenige von (2R,2'S)-3',4'-Didehydro-1 ',2'-dihydro-2-(4-hydroxy-3-methylbut-2-enyl)-2'-(3-methylbut-2-enyl)-~, Y-carotin-1'-01 zukommt. Kurzlich haben wir uber die Synthese von zwei optisch aktiven C,,-Bausteinen sowie des C,,-Carotinoids C.p. 450 in optisch aktiver Form ausgehend von (-)$-Pinen berichtet [ 11.-1 In der vorliegenden Arbeit berichten wir uber die Synthese von optisch aktivem C.p. 473 (1) sowie eines weiteren optisch aktiven C,,-Bausteins, welcher, wie ursprunglich fur C.p. 450 vorgeschlagen [2] [3], zwei potentielle OH-Gruppen in der Prenyl-Seitenkette aufweist . Ergebnisse und Diskussion. -1. Synthese des optisch aktiven C,-Bausteins (R) -16. Das Ausgangsmaterial (R)-2 (hergestellt aus (-)$-Pinen in 11 Stufen gemass [l]) wurde zunachst mit Ac,O/Pyridin und 4-(Dimethy1amino)pyridin als Katalysator zu (R)-3 ') 4. Mitteilung, s. [I].

Synthesis of(+)‐(2S, 6S)‐trans‐α‐Irone and of(‐)‐(2S, 6S)‐trans‐γ‐Irone

“…was reduced to alcohol (-)-(S)-10 [23] ([a]'," = -30.6 (c = 1.0, CHCI,)). These two [ a ] values correspond to 82 and 73.5% e.e., respectively, when compared with the values of Pfander et al [21], indicating a slight racemisation during LiAlH, reduction of (-)-(S)-9. ")…”

Isolation of a New Carotenoid and Two New Carotenoid Glycosides fromCurtobacterium flaccumfaciens pvar poinsettiae

“…The determination of the configuration at C(2) and C(2') of the aglycon is based on the CD spectra (À 1808, Et 2 O/isopentane/EtOH 5 : 5 : 2) of 4 and 5 which are identical with that of synthetic C.p. 450 ((all-E,2R,2'R ); 1) [9] and C.p. 473 ((all-E,2R,2'S ); 2) [10], respectively, demonstrating the (2R,2'R )-configuration for 4 and the (2R,2'S )-configuration for 5.…”

“…450 ((all-E,2R,2'R ); 1) [9] and C.p. 473 ((all-E,2R,2'S ); 2) [10], respectively, demonstrating the (2R,2'R )-configuration for 4 and the (2R,2'S )-configuration for 5.…”

“…C-COSY, T-ROESY, and HMBC experiments, all protons and C-atoms can unambiguously be assigned, and the presence of the 3,4-dihydroanhydrobacterioruberin end group is established. Based on the comparison of the CD spectra of synthetic 2 ((all-E,2R,2'S)) exhibiting a positive maximum at 235 nm and a negative maximum at 304 nm [10], with isolated 6 exhibiting a positive maximum at 255 nm and a negative maximum at 298 nm, the configuration of 6 is tentatively assigned as (2R,2'R). The UV/VIS, MS, NMR, and CD data of 6 are consistent with the structure of (all-E,2R,2'R)-2-(4-…”

C45‐ and C50‐Carotenoids Part7 Total synthesis of (all‐E,2R,6R,2′R,6′R)‐ and (all‐E,2R,6S,2′R,6′S)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐γ,γ‐carotene (sarcinaxanthin)

“…450 [S] and C.p. 473 [6], both containing a a-end group, as well as of decaprenoxanthin [l] with the &-end group. In view of the elucidation of the configuration of natural 1, we report in the present paper the synthesis of (all-E,2R,6R,2'R,6R)-and (all-E,2R,6S,2'R,6'S)-sarcinaxanthin ((all-E,2R,6R,2'R,6'R)-and (all-E,2R,6S,TR, 6'S)-1, resp.…”