Synthese von (R)-β, β-Carotin-2-ol und (2R, 2′R)-β, β-Carotin-2,2′-diol

Synthesis of (R)-β, β-Caroten-2-ol and (2R, 2′R)-β, β-Carotene-2,2′-diol Starting from geraniol, the two carotenoids (R)-β, β-caroten-2-ol ( 1 ) and (2R, 2′R)-β, β-carotene-2,2′-diol ( 3 ) were synthesized. The optically active cyclic building block was obtained by an acid-catalysed cyclisation of the epoxide (R)- 4 . The enantiomeric excess of the product was > 95 %.     

Eine Suche nach 3′-Epilutein ( = (3R,3′S,6′R)-β,ε-Carotin-3,3′-diol) und 3′, O-Didehydrolutein (=(3R, 6′R)-3-Hydroxy-β,ε-carotin-3′-on) in Eigelb,in Blüten von Caltha palustris und in Herbstblättern

Search for the Presence in Egg Yolk, in Flowers of Caltha palustris and in Autumn Leaves of 3′-Epilutein ( =(3R,3′S,6′R)-β,ε-Carotene-3,3′-diol) and 3′,O-Didehydrolutein ( =(3R,6′R)-3-Hydroxy-β,ε-carotene-3′-one) 3′.O-Didehydrolutein ( =(3R, 6′R)-3-hydroxy-β,ε-carotene-3′-one; 2) has been detected in egg yolk and in flowers of Caltha palustris. This is the first record for its occurrence in a plant. The compound shows a remarkable lability towards base; therefore, it may have been overlooked til now, because it is destroyed under the usual conditions of saponification of the carotenoid-esters. One of the many products formed from 2 with 1% KOH in methanol has been purified and identified as the diketone 3 ( =(3R)-3-hydroxy-4′, 12′-retro-β,β-carotene-3′,12′-dione). The identification of this transformation product from lutein might throw a new light on the metabolism of this important carotenoid in green plants. 3′-Epilutein ( =(3R,3′S,6′R)-β,ε-carotene-3,3′-diol; 1) was not detected in egg yolk, but is present besides lutein in flowers of C. palustris, thus confirming an earlier report of the occurrence of an isomeric (possibly epimeric) lutein (‘calthaxanthin’) in that plant [21]. We were not able to detect even traces of 1 or 2 in the carotenoid fraction from autumn leaves of Prunus avium (cherry), Parrotia persica, Acer montanum (maple) and yellow needles of Larix europaea (larch). α-Cryptoxanthin (4) , a very rare carotenoid, was isolated in considerable quantity for the first time from flowers of C. palustris.     

Absolute Konfiguration von Loroxanthin (=(3R, 3′R, 6′R)-β, ϵ-Carotin-3, 19, 3′-triol)

Absolute Configuration of Loroxanthin (=(3R, 3′R, 6′R)-β, ?-Carotene-3, 19, 3′-triol) ‘Loroxanthin’, isolated from Chlorella vulgaris, was separated by HPLC. methods in two major isomers, a mono-cis-loroxanthin and the all-trans-form. Solutions of the pure isomers easily set up again a mixture of the cis/trans-isomers. Extensive ¹H-NMR. spectral measurements at 400 MHz allowed to establish the 3′, 6′-trans-configuration at the ?-end group in both isomers and the (9E)-configuration in the mono-cis-isomer. The absolute configurations at C(3) and C(6′) were deduced from CD. correlations with synthetic (9Z, 3R, 6′R)-β, ?-carotene-3, 19-diol ( 5 ) and (9E, 3R, 6′R)-β, ?-carotene-3, 19-diol ( 6 ), respectively. Thus, all-trans-loroxanthin ( 3 ) is (9Z, 3R, 3′R, 6′R)-β, ?-carotene-3, 19, 3′-triol and its predominant mono-cis-isomer is (9E, 3R, 3′R, 6′R)-β, ?-carotene-3, 19, 3′-triol ( 4 ). Cooccurrence in the same organism and identical chirality at all centers suggest that loroxanthin is biosynthesized from lutein ( 2 ).     

Synthese und Chiralität von (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,β-carotin und (5R, 6R)-5,6-Dihydro-β,β-carotin-5,6-diol,einem Carotinoid mit ungewöhnlichen Eigenschaften

Synthesis and Chirality of (5S,6R)-5,6-Epoxy-5,6-dihydro-β,β-carotene and (5R,6R)-5,6-Dihydro-β,β-carotene-5,6-diol, a Compound with Unexpected Solubility Characteristics Wittig-condensation of azafrinal ( 1e ) with the phosphorane derived from 7 leads to a (1:3)-mixture of (E)-9′- and (Z)-9′-β,β-carotene-diol 3 , from which pure and optically active 3 ((5R,6R)-5,6-dihydro-β,β-carotene-5,6-diol) has been isolated as bright violet leaflets, m.p. 168°. Due to the trans-configuration of the diol moiety and to severe steric hindrance, hydrogen bonding is reduced to such an extent, that 3 behaves much more as a hydrocarbon than as a diol. There is good evidence that the so-called ‘β-oxycarotin’ obtained by Kuhn & Brockmann [15] by chromic acid oxidation of β, β-carotene is the corresponding racemic cis-diol. 3 has been converted into (5S, 6R)-5,6-epoxy-5.6-dihydro-β,β-carotene ( 4 ), m.p. 156°. This transformation establishes for the first time the chirality of a caroteneepoxide (without other O-functions). Full spectral and chiroptical data including a complete assignement of ¹³C-chemical shifts for azafrin methyl ester and 3 are presented.     

Synthese und Chiralität von (5R, 6R)-5,6-Dihydro-β, ψ-carotin-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotin-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β, ψ-carotin und (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-carotin

Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-carotene Wittig-condensation of optically active azafrinal ( 1 ) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol ( 2 ) and (+)-(R)-α-ionol ( 5 ) leads to the crystalline and optically active carotenoid diols 4 and 7 , respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9 , respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2].     

Synthese von (−)-(R)-Nephthenol und (−)-(R)-Cembren A

Synthesis of (?)-(R)-Nephthenol and (?)-(R)-Cembren A Starting for L -serine,(?)-(R)-nephthenol((?)- 2 ) and (?)-(R)-cembren A((?)- 3 ) were synthesized.     

Carotinoide mit 7-Oxabicyclo[2.2.1]heptyl-Endgruppen. Teil I. Versuch einer Synthese von Cycloviolaxanthin (= (3S,5R,6R,3′S,5′R,6′R)-3,6:3′,6′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin-5,5′-diol)

Carotenoids with 7-Oxabicyclo[2,2.1]heptyl End Groups. Attempted Synthesis of Cycloviolaxanthin ( = (3S,5R,6S,3′S,5′R,6′R)-3,6:3′,6′- Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin-5,5′-diol) Starting from our recently described synthon (+)- 24 , the enantiomerically pure 3,6:4,5:3′,6′:4′,5′-tetraepoxy-4,5,4′,5′-tetrahydro-ε,ε-carotene ( 34 ) and its 15,15′-didehydro analogue 32 were synthesized in eleven and nine steps, respectively (Scheme 4). Chiroptical data show, in contrast to the parent ε,ε-carotene, a very weak interaction between the chiral centers at C(5), C(5′), C(6), C(6′), and the polyene system. Diisobutylaluminium hydride reduction of 32 lead rather than to the expected 15,15′-didehydro analogue 35 of Cycloviolaxanthin ( 8 ), to the polyenyne 36 (Scheme 5). We explain this reaction by an oxirane rearrangement leading to a cyclopropyl ether followed by a fragmentation to an aldehyd on the one side and an enol ether on the other (Scheme 6). This complex rearrangement includes a shift of the whole polyenyne chain from C(6), C(6′) to C(5), C(5′) of the original molecule.     

New Olefinic Cyclizations by Oxymetallation. Conversion of (−)-elemol to (−)-selina-4α, 11-diol (cryptomeridiol) and (−)-guai-1 (10)-ene-4α, 11-diol

Acetoxythallation of (?)-elemol acetate ( 1b ) yields a diacetate 2b which after treatment with lithium aluminium hydride gives (?)-guai-1 (10)-ene-4α, 11-diol ( 2a ). (?)-Elemol ( 1a ) is converted to (?)-selina-4α, 11-diol ( 9 , cryptomeridiol) by hydroxymercuration followed by reductive demercuration. (+)-γg-Elemene ( 5 ) similarly yields (+)-selin-7(11)-en-4α-ol ( 11 , juniper camphor). The stereochemistry and mechanism of these metal salt-induced olefinic cyclization and their biogenetic implication are discussed.     

Synthesis and structure of (4R,5R)-α,α,α′,α′-2,2-hexaphenyl-4,5-dimethanol-1,3-dioxolane

We report the synthesis of the 1,4-diol (4R,5R)-α,α,α′,α′-2,2-hexaphenyl-4,5-dimethanol-1,3-dioxolane from dimethyl-L-tartrate and benzophenone. The X-ray and the IR structural studies on show that this compound has a preferred conformation with OHPh interactions which are different from related compounds.     

C45- und C50-Carotinoide. 4. Mitteilung. Synthese von optisch aktiven cyclischen C20-Bausteinen und von (2R,2′R)-2,2′-Bis(4-hydroxy-3-methyl-2-butenyl)-β,β-carotin ( = C.p. 450)

C₄₅- and C₅₀-Carotenoids: Synthesis of Optically Active Cyclic C₂₀-Building Blocks and of (2R,2′R)-2,2′-Bis(4-hydroxy-3-methyl-2-butenyl)-β,β-carotene ( = C.p. 450) The synthesis of the optically active C₂₀-building blocks (R)- 26 and (R)- 39 and of the optically active cyclic C₅₀-carotenoid C.p. 450 ( 3 ) starting from (?)-β-pinene is reported.     

Synthese und Reaktionen von Metallkomplexen mit porphinoidem Ligandsystem 1. Mitteilung (3,3,4,4-Tetramethyl-5-imino-1-pyrrolin-2-yl)-(3′,3′,4′,4′-tetramethyl-5′-iminopyrrolidin-2′-yliden)-methan,ein Zwischenprodukt zur Synthese von Hexahydroporphinen

Reaction of tetramethylsuccinicdinitrile with methylmagnesium iodide in boiling toluene leads to the title compound 8 in 80–85% yield. The magnesium complex of 2-imino-3,3,4,4-tetramethyl-5-methylidene-pyrrolidine is shown to act as an intermediate.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Verbindungen. III. Synthese von (+)-Abscisinsäure, (−)-Xanthoxin, (−)-Loliolid, (−)-Actinidiolid und (−)-Dihydroactinidiolid

Synthesis of optically active natural carotenoids and structurally related compounds. III. Synthesis of (+)-abscisic acid, (?)-xanthoxin, (?)-loliolide, (?)-actinidiolide, and (?)-dihydroactinidiolide The syntheses of (+)-abscisic acid ( 1 ), (?)-xanthoxin ( 2 ), (?)-loliolide ( 3 ), (?)-actinidiolide ( 4 ), and of (?)-dihydroactinidiolide ( 5 ) from one common starting material are reported. The syntheses yield also some enantiomeric or diastereomeric analogues.     

Cycloviolaxanthin (= (3S,5R,6R,3′S,5′R,6′R)-3,6:3′,6′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin-5,5′-diol), ein neues Carotinoid aus Paprika (Capsicum annuum)

Cycloviolaxanthin (= (3S,5R,6R,3′S,5′R,6′R)-3.6:3′,6′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene-5,5′-diol), a Novel Carotenoid from Red Paprika (Capsicum annuum) From red paprika (Capsicum annuum var. longum nigrum) cycloviolaxanthin was isolated as a minor carotenoid and, based on spectral data, assigned the symmetrical structure 8 .     

Photochemie von tricyclischen β, γ-γ′, δ′-ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen

Photochemistry of tricyclic β, γ-γ′, δ′-unsaturated ketones The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3-acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4 . However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa-di-π-methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6 . The conversion 5 → 6 represents a novel photochemical 1,4-acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4-acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2 , respectively, underwent a 1,3-acyl shift upon irradiation followed by decarbonylation, and the oxa-di-π-methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ-unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6).     

Isolierung,Konstitution und Synthese der (R)-(−)-Eucominsäure

From the bulbs of Eucomis punctata L'Hérit. (Liliaceae) and of a hitherto undefined species of Eucomis a new optically active phenolic carboxylic acid, eucomic acid, was isolated. Structure 1 was assigned on the basis of chemical and spectral evidence. The absolute configuration of eucomic acid was determined by its correlation with piscidic acid ((2 R, 3 S)-2-(4′-hydroxybenzyl)-tartaric acid) ( 8 ). Consequently, eucomic acid is (R)-(?)-2-(4′-hydroxybenzyl)-malic acid ( 1 ). For the stereospecific synthesis, methyl cis-p-methoxybenzylidene-succinic acid ( 22 ) was transformed into the γ-lactone 24 which, by catalytic hydrogenolysis, yielded (±)-2-(4′-hydroxybenzyl)-malic acid 1-methyl ester ( 27 ). Resolution with (?)-quinine led to the enantiomeric acids 29 and 30 . The methyl ester of the levorotatory enantiomer 30 was identical with the dimethyl ester 3 of 4′-O-methyl-eucomic acid.     

Synthese von diastereo- und enantio-selektiv deuterierten β,ε-, β,β-, β,γ- und γ,γ-Carotinen

Synthesis of Diastereo- and Enantioselectively Deuterated β,ε-, β,β-, β,γ- and γ,γ-Carotenes We describe the synthesis of (1′R, 6′S)-[16′, 16′, 16′-²H₃]-β, εcarotene, (1R, 1′R)-[16, 16, 16, 16′, 16′, 16′-²H₆]-β, β-carotene, (1′R, 6′S)-[16′, 16′, 16′-²H₃]-γ, γ-carotene and (1R, 1′R, 6S, 6′S)-[16, 16, 16, 16′, 16′, 16′-²H₆]-γ, γ-carotene by a multistep degradation of (4R, 5S, 10S)-[18, 18, 18-²H₃]-didehydroabietane to optically active deuterated β-, ε- and γ-C₁₁-endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C₁₁ → C₁₄; C₁₄+C₁₂+C₁₄→C₄₀. NMR.- and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all-(E)-[²H₆]-β,β-carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.-effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′-²H₆]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.- and CD.-spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented.     

Isolierung von (2S, 4S)-(+)-γ-Hydroxynorvalin und (2S, 4R)-(−)-γ-Hydroxynorvalin aus Boletus satanas Lenz

We have isolated from the carpophores of Boletus satanas Lenz (Basidiomycetae) (2S,4S)-(+)-γ-hydroxynorvaline ( 1 ) and (2S,4R)-(?)-γ-hydroxynorvaline ( 2 ). The chirality of each diastereomer has been determined by chemical synthesis starting from optically active precursors and by application of different chiroptical methods. Gaschromatographic separation of the derived diastereomeric N-[(S)-α-methoxypropionyl]-lactones reveals that the optical purity of natural 2 is 88% whereas 1 exists as a partial racemate: (2S,4S): (2R,4R) = 3:2. Muscarine could not be detected in the carpophores of B. satanas, contrary to some literature data but basic substances of unknown structure are present in low concentration.     

Nachweis von Fragment-Genesen im Massenspektrometer 1. Mitteilung Struktur des Schlüsselfragmentes von Bisamidin ((3,3,4,4-Tetramethyl-5-imino-1-pyrrolin-2-yl)-(3′,3′,4′,4′-tetramethyl-5′-iminopyrrolidin-2′-yliden)-methan), einem Zwischenprodukt zur Synthese von Hexahydroporphinen

The structure of the fragment-ion m/e 178 of the title compound was elucidated by the analysis of its formation and its subsequent fragmentation, using DADI, defocussing, peak matching, and deuterium labeling.