Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. IX. Synthese von (3R)-Hydroxyechinenon, (3R, 3′R)- und (3R, 3′S)-Adonixanthin, (3R)-Adonirubin,deren optischen Antipoden und verwandten Verbindungen

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. IX. Synthesis of (3R)-Hydroxyechinenone, (3R, 3′R)- and (3R, 3′S)-Adonixanthin, (3R)-Adonirubin, Their Optical Antipodes and Related Compounds The synthesis of racemic and optically active hydroxyechinenone ( 12–14 ), adonixanthin ( 16–19 ), adonirubin ( 22–24 ), meso-astaxanthin ( 26 ) and their corresponding diosphenols 15, 20, 21, 25, 27, 28 , and 29 ) by Wittig reaction is reported, starting from suitable C₁₅-phosphonium salts and C₁₀-aldehydes.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. VIII. Synthese von (3S,3′S)-7,8,7′,8′-Tetradehydroastaxanthin und (3S,3′S)-7,8-Didehydroastaxanthin (Asterinsäure)

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. VIII. Synthesis of (3S,3′S)-7,8,7′,8′-Tetradehydroastaxanthin and (3S,3′S)-7,8-Didehydroastaxanthin (Asterinic Acid) The synthesis of all-trans-(3S,3′S)-3,3′-dihydroxy-7,8, 7′,8′-tetradehydro-β, β-carotene-4,4′-dione ( 1 ), of all-trans-(3S,3′S)-3,3′-dihydroxy-7, 8-didehydro-β,β-carotene-4,4′-dione ( 2 ) (asterinic acid = mixture of 1 and 2 ), and of their 9,9′-di-cis- and 9-cis-isomers is reported starting from (4′S)(2E)-5-(4′-hydroxy-2′, 6′,6′-trimethyl-3′-oxo-l′-cyclohexenyl)-3-methyl-2-penten-4-ynal ( 8 ). The absolute configuration (3S,3′S) for both components 1 and 2 of asterinic acid ex Asterias rubens is confirmed on the basis of spectroscopic and direct comparison.     

C45 und C50-Carotinoide. 6. Mitteilung. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-ϵ, ϵ-carotin)

C₄₅- and C₅₀-Carotenoids: Synthesis of an Optically Active Cyclic C₂₀-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-?, ?-carotene) The synthesis of the optically active cyclic C₂₀-building block (R, R) -15 and of the optically active C₅₀-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin ( 1 ) starting from (-)-β-pinene ((S)- 2 ) is reported.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. IV. Synthese von (3R, 3′R, 6′R)-Lutein. Vorläufige Mitteilung

Synthesis of optically active natural carotenoids and structurally related compounds. IV. Synthesis of (3R, 3′R, 6′R)-lutein The synthesis of (3R, 3′R, 6′R)-lutein ( 19 ) according to the building principle C₂₅+C₁₅?C₄₀ is reported utilizing (R)-4-hydroxy-2,6,6-trimethyl-2-cyclohexen-1-one ( 4 ) as a readily available key intermediate.     

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.     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6-Oxo-isophoron. IV. Neues Konzept für die Synthese von (3RS, 3′RS)-, (3S, 3′S)- und (3R, 3′R)-9,9′-dicis-7,8,7′,8′-Tetradehydroastaxanthin

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. IV. A Novel Concept for the Synthesis of (3RS, 3′RS)-, (3S, 3′S)- and (3R, 3′R)-9,9′-dicis-7,8,7′,8′-Tetradehydroastaxanthin Starting from readily available intermediates of the synthesis of astaxanthin, (3RS, 3′RS)-, (3R, 3′R)- and (3S, 3′S)-9,9′-di-cis-tetradehydroastaxanthin ( 1, 1a and 1b , resp.) were synthesized, 1 and 1b for the first time. Key features of this concept are: a) use of the unprotected, acetylenic phosphonium salts 8–12 , b) a two-step synthesis with 47% overall yield, and c) good chemical and optical purity of the end products.     

Temperaturabhängiger Circulardichroismus von (3S, 3′R)- und (3S, 3′ S)-Adonixanthin

The temperature dependent CD. spectra of (3S, 3′R)- and (3S, 3′S)-adonixanthin are compared with those of (3R, 3′R)-zeaxanthin ( 1 ) and (3S, 3′S)-astaxanthin ( 2 ). The room temperature spectra of 1 and 2 are quite similar. On cooling to ?180° the CD. of 1 simply intensifies, the CD. of 2 changes sign and becomes also very intense. The room-temperature CD. of (3S, 3′R)-adonixanthin ( 3 ) resembles closely those of 1 and 2 at room temperature. On cooling, however, it becomes weak and changes strongly its shape. With (3S, 3′S)-adonixanthin ( 4 ) it is the low-temperature spectrum which resembles that of 2 at low temperature, whereas the room-temperature spectrum is weak and quite different in shape. These observations can be explained with temperature dependent equilibria where the end groups are twisted out of the plain of the chain thereby conferring chirality to the conjugated system.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. II. Synthese von (3 S, 3′S)-Astaxanthin

Synthesis of optically active natural carotenoids and structurally related compounds. II. Synthesis of (3S, 3′S)-astaxanthin The syntheses of rac. astaxanthin, (3 S, 3′S)-astaxanthin ( 1 ), its 15-cis isomer ( 21 ), its diacetate ( 22 ), and of (3 S, 3′ S)-15, 15′-didehydroastaxanthin ( 20 ) are reported.     

Synthese der (3S,4R,3′S,4′R)- und (3S,4S,3′S,4′S)Crustaxanthine sowie weiterer Verbindungen mit 3,4-Dihydroxy-β-Endgruppen

Synthesis of (3S,4R,3′S,4′R)- and (3S,4S,3′S,4′S)-Crustaxanthins and Further Compounds with 3,4-Dihydroxy β-End-groups Starting from 3 , the enantiomerically pure title compounds were synthesized in eight steps. Spectra and HPLC systems are presented that allow a distinction between these isomers.     

Synthesen von optisch aktiven Carotinoiden mit einer (R)-4-Hydroxy-β-Endgruppe

Synthesis of Optically Active Carotenoids with (R)-4-Hydroxy β-End Groups We describe the synthesis of optically active iso-β-kryptoxanthin ( 12 ; (R)-β,β-caroten-4-ol), iso-α-kryptoxanthins 14 ((4R,6′RS)-β,ε-caroten-4-ol) and 16 ((4R,6′R)-β,ε-caroten-4-ol), 4′-hydroxyechinenone ( 18 ; (R)-4′-hydroxy-β,β-caroten-4-one), and isorubixanthin ( 20 ; (R)-β,ω,-caroten-4-ol), their 400-MHz-¹H-NMR spectra, CD spectra and HPLC behaviour.     

Carotinoide mit 7-Oxabicyclo[2.2.1]heptyl-Endgruppen. Teil II. Synthese von (2S,5R,6S,2′S,5′R,6′S)-2,5:2′5′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotin

Carotenoids mit 7-Oxabicyclo[2.2.1]heptyl-End Groups. Synthesis of (2S,5R,6S,2′S,5′R,6′S)-2,5:2′5′-Diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene Mukayama's ester 6 (methyl (1S,2R,5S)-2,5-epoxy-2,6,6-trimethylcyclohexane-1-carboxylate) was transformed in a few conventional steps into the title compound 14 . Its CD curve was found to be significantly different from that of the analogous 3,6-epoxide, a fact we tentatively lake as an indication of a (weak) electronic interaction between the ring O-atom and the π-orbitals of the polyene chain.     

Photochemische Umsetzung von optisch aktiven 2-(1′-Methylallyl)anilinen mit Methanol

Photochemical Reaction of Optically Active 2-(1′-Methylallyl)anilines with Methanol It is shown that (?)-(S)-2-(1′-methylallyl)aniline ((?)-(S)- 4 ) on irradiation in methanol yields (?)-(2S, 3R)-2, 3-dimethylindoline ((?)-trans- 8 ), (?)-(1′R, 2′R)-2-(2′-methoxy-1′-methylpropyl)aniline ((?)-erythro- 9 ) as well as racemic (1′RS, 2′SR)-2-(2′-methoxy-1′-methylpropyl) aniline ((±)-threo- 9 ) in 27.1, 36.4 and 15.7% yield, respectively (see Scheme 3). By deamination and chemical correlation with (+)-(2R, 3R)-3-phenyl-2-butanol ((+)-erythro- 13 ; see Scheme 4) it was found that (?)-erythro- 9 has the same absolute configuration and optical purity as the starting material (?)-(S)- 4 . Comparable results are obtained when (?)-(S)-N-methyl-2-(1′-methylallyl)aniline ((?)-(S)- 7 ) is irradiated in methanol, i.e. the optically active indoline (+)-trans- 10 and the methanol addition product (?)-erythro- 11 along with its racemic threo-isomer are formed (cf. Scheme 3). These findings demonstrate that the methanol addition products arise from stereospecific, methanol-induced ring opening of intermediate, chiral trans, -(→(?)-erythro-compounds) and achiral cis-spiro [2.5]octa-4,6-dien-8-imines (→(±)-threo-compounds; see Schemes 1 and 2).     

C45- and C50-Carotehoids. Part 8. Synthesis of (all-E,2S,2′S)-bacterioruberin, (all-E,2S,2′S)-monoanhydrobacterioruberin, (all-E,2S,2′S)-bisanhydrobacterioruberin, (all- E,2R,2′R)-3,4,3′,4′-tetrahydrobisanhydro- bacterioruberin,and (all-E,S)-2-isopentenyl-3,4-dehydrorhodopin

Starting from (R)-3-hydroxybutyric acid ((R)- 10 ) the C₄₅- and C₅₀-carotenoids (all-E,2S,2′S)-bacterioruberm ( 1 ), (all-E,2S,2′S)-monoanhydrobacterioruberin ( 2 ), (all-E,2S,2′S)-bisanhydrobacterioruberin ( 3 ), (all-E,2R,2′R)-3,4,3′,4′-tetrahydrobisanhydrobacterioruberin ( 5 ), and (all-E,S)-2-isopentenyl-3,4-dehydrorhodopin ( 6 ) were synthesized. By comparison of the chiroptical data of the natural and the synthetic compounds, the (2S)- and (2′S)-configuration of the natural products 1–3 and 6 was established.     

Stereochemische Korrelationen zwischen (2R,4′R,8′R)-α-Tocopherol, (25S,26)-Dihydroxycholecalciferol, (–)-(1S,5R)-Frontalin und (–)-(R)-Linalol

Stereochemical Correlations between (2R,4′R,8′R)-α-Tocopherol, (25S,26)-Dihydroxycholecalciferol, (–)-(1S,5R)-Frontalin and (–)-(R)-Linalol The optically active C₅- and C₄-building units 1 and 2 with their hydroxy group at a asymmetric C-atom were transformed to (–)-(1S,5R)-Frontalin ( 7 ) and (–)-(3R)-Linalol ( 8 ) respectively; 1 and 2 had been used earlier in the preparation of the chroman part of (2R,4′R,8′R)-α-Tocopherol ( 6a , vitamin E), and for introduction of the side chain in (25S,26)-Dihydroxycholecalciferol ((25S)- 4 ), a natural metabolite of Vitamin D₃. The stereochemical correlations resulting from these converions fit into a coherent picture with those correlations already known from literature and they confirm our earlier stereochemical assignments. A stereochemical assignment concerning the C(25)-epimers of 25,26-Dihydroxycholecalciferol that was in contrast to our findings and that initiated the conversion of 1 and 2 to 7 resp. 8 for additional stereochemical correlations has been corrected in the meantime by the authors [26].     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus Oxo-isophoron. I. Modifizierung der Kienzle-Mayer-Synthese von (3S 3′S)-Astaxanthin

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. I. Modification of the Kienzle-Mayer-Synthesis of (3S, 3′S)-Astaxanthin An efficient synthesis of (3S, 3′S)-astaxanthin ( 1a ) in high yield and optical purity starting from (4R, 6R)-4-hydroxy-2,2,6-trimethylcyclohexanone ( 4 ) is reported. The absolute configuration of 1a , previously derived from ORD. data, has been confirmed by X-ray analysis of 5 , a derivative of 6-oxo-isophorone ( 2 ). The key features of the improved synthesis are the two-step conversion of 4 to the key intermediate (4S)-2,6,6-trimethyl-4-hydroxy-2-cyclohexen-1-one ( 14 ), a new method for the partial reduction of the sterically hindered triple bond of (S)-6-hydroxy-3-(5-hydroxy-3-methyl-3-penten-1-ynyl)-2,4,4-trimethyl-2-cyclohexen-1-one ( 32 ), and Wittig olefination of the dialdehyde 1,6-dimethyl-1,3,5-octatrienedial ( 38 ) using phosphonium salt 37 with a free hydroxyl group.     

Synthese von optisch aktiven,natürlichen Carotinoiden und strukturell verwandten Naturprodukten. VII. Synthese von (3R)-3-Hydroxyretinol, (3R)-3-Hydroxyretinal und (3R)-3-Hydroxyretinsäure

Synthesis of optically active natural carotenoids and structurally related compounds. VII. Synthesis of (3R)-3-hydroxyretinol, (3R)-3-hydroxyretinal and (3R)-3-hydroxyretinoic acid The synthesis of (3R)-3-hydroxyretinol, ( 7 ), (3R)-3-hydroxyretinal ( 9 ) and (3R)-3-hydroxyretinoic acid ( 5 ) according to the building principle C₁₅ + C₅ = C₂₀ is reported utilizing the optically active C₁₅-phosphonium salt 2 and the C₅-aldehyde ester 3 .     

Beitrag zur Analytik und Synthese von 3-Hydroxy-4-oxocarotinoiden

Contribution to the Analytical Separation and the Synthesis of 3-Hydroxy-4-oxocarotenoids (3RS,3′RS)-Astaxanthin (= 3,3′-dihydroxy-β,β-carotene-4,4′-dione, 1:1-mixture of racemate and meso-form; 1 ) can be separated into its optical isomers (3S,3′S)- 1a , (3R,3′R)- 1b and meso-(3R,3′S)- 1c via the corresponding diastereomeric di-(?)-camphanates. Some aspects of the configurational stability of astaxanthin are discussed. - HPLC. analysis of the (?)-camphanates of 3-hydroxy-4-oxocarotenoids provides, in suitable cases and supported by spectroscopic data, an analytical method for the simultaneous determination of constitution and chirality.     

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].     

Neue Synthese von (−)-(R)-Cembren A,Synthese von (+)-(R)-Cembrenen und (+)-(S)-Cembren

Novel Synthesis of (?)-(R)-Cembrene A, Synthesis of (+)-(R)-Cembrenene and (+)-(S)-Cembrene A novel synthesis of (?)-(R)-cembrene A ((?)- 3 ) was developed using the Sharpless epoxidation for the introduction of the chiral center. Furthermore, the synthesis of (+)-(R)-cembrenene ((+)- 4 ) showed that this cembranoid must have the (R)-configuration and not, as previously reported, the (S)-configuration. Selective hydrogenation of (+)- 4 afforded (+)-(S)-cenibrene ((+)- 5 ).     

Synthese von (−)-(5R,6S)-5,6-Epoxy-5,6-dihydro-β-ionon

Synthesis of (?)-(5R,6S)-5,6-epoxy-5,6-dihydro-β-ionone Optically active 5,6-epoxy-5,6-dihydro-β-ionones have been prepared for the first time and their absolute configurations were determined by correlation with (?)-(S)-α-ionone. Acid catalyzed hydrolysis of the epoxide proceeds with retention of the configuration at C(6) and with inversion at C(5).