Separation of (3R, 3′ R)-, (3R, 3′ S; meso)-, (3S, 3′ S)- Zeaxanthin, (3R, 3′ R, 6′ R)-, (3R, 3′ S, 6′ S)- and (3S, 3′ S, 6′ S)-Lutein via the dicarbamates of (S)-(+)-α-(1-naphthyl) ethyl isocyanate

A method is described for the qualitative and quantitative determination of configurational isomers of zeaxanthin (=3,3′ -dihydroxy-β, β -carotene) and lutein (=3,3′ -dihydroxy-α -cartotene). It is based on the reaction of these zeaxathin and lutein isomers with (S)-(+)-α-(1-naphthyl) ethyl isocyanate to afford diastereomeric dicarbamates, which are analyzed by HPLC.     

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 .     

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.     

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)

The synthesis of sarcinaxanthin ((2R,6R,2′R,6′R)- 1 ), a symmetrical C₅₀-carotenoid with two γ-end groups, isolated from Sarcina lutea and from Cellulomonas biazotea as major pigment, was based on the strategy C₂₀ + C₁₀ + C₂₀ = C₅₀ using camphoric acid as starting material for the C₂₀-end group 3. The key step of the synthesis is a ring enlargement of the cyclopentane derivative 10 with 2,4,4,6-tetrabromocyclohexa-2,5-dien-1-one (TBCO) to give the cyclohexane derivative 11 (Scheme 1). The spectroscopic data of the synthetic compound are in full agreement with the data of the isolated product and give the final proof for the (2R,6R,2′R,6′R) chirality of natural sarcinaxanthin.     

Isolation and Characterisation of (5R, 6S,5′R,8′R)- and (5R,6S,5′R,8′S)-Luteochrome from Brazilian Sweet Potatoes (Ipomoea batatas LAM.)

Luteochrome isolated from the tubers of a white-fleshed variety of sweet potato (Ipomoea batatas LAM .) has been shown by HPLC, ¹H-NMR and CD spectra to consist of a mixture of (5R,6S,5′R,8′R)- and (5R,6S,5′R,8′S)- 5,6:5′,8′-diepoxy-5,6,5′,8′-tetrahydro-β,β-carotene ( 1 and 2 , resp.). Therefore, its precursor is (5R,6S,5′R,6′S)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene ( 4 ). This is the first identification of luteochrome as a naturally occurring carotenoid and, at the same time, gives the first clue to the as yet unknown chirality of the widespread β,β-carotene diepoxide. These facts demonstrate that the enzymic epoxidation of the β-end group occurs from the α-side, irrespective of the presence of OH groups on the ring.     

Separation of (3S, 3′S)-, (3R 3′R)- and (3S, 3′R)-astaxanthin via (−)-camphanic acid esters

A method is described for the qualitative and quantitative determination of configurational isomers of astaxanthin. It is based on the esterification of astaxanthin with (—)-camphanic acid chloride and analysis of the corresponding diesters by HPLC.     

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.     

Heterotricyclodecane XX (+)-(1S, 3S, 6S, 8S)- und (−)-(1R, 3R, 6R, 8R)-2, 7-Dioxa-twista-4,9-dien

(+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-2,7-dioxa-twista-4,9-diene. A synthesis and the determination of the sense of chirality of (+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-2,7-dioxa-twista-4,9-diene ((+)- 5 and (?)- 5 , respectively) is described.     

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].     

5-(α-Fluorovinyl)tryptamines and 5-(α-Fluorovinyl)-3-(N-methyl-1′,2′,5′,6′,-tetrahydropyridin-3′- and -4′-yl)indoles—5-(α-Fluorovinyl)tryptamines

5-(α-Fluorovinyl)tryptamines 4a, 4b and 5-(α-fluorovinyl)-3-(N-methyl-1′,2′,5′,6′-tetrahydropyridin-3′- and -4′-yl) indoles 5a, 5b were synthesized using 5-(α-fluorovinyl)indole ( 7 ). The target compounds are bioisosteres of 5-carboxyamido substituted tryptamines and their tetrahydropyridyl analogs.     

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].     

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.     

Total synthesis of 5R,5-(1''''R-hydroxy-2''''-phenylethyl)-γ-lactone

The latest and highly efficient asymmetric dihydroxylation was employed to create the chiral vicinal dihydroxy group of the title compound 1, which has been synthesized from phenylacetaldehyde through 6 steps with a total yield of 61%.     

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.     

(+)-(1S,2S,5R)-8-联苯薄荷醇的合成

以(R)-( )-pu legone为起始原料,经1,4-加成,还原两步反应合成了手性辅助试剂( )-(1S,2S,5R)-8-联苯薄荷醇及其差向异构体(-)-(1R,2S,5R)-8-联苯薄荷醇,总产率95%。其结构经1H NMR,13C NMR,IR,MS和X-射线衍射仪表征。     

(+)-(1S, 3S, 6S, 8S)-und (−)-(1R, 3R, 6R, 8R)-4, 9-Twistadien: Synthese und Bestimmung der absoluten Konfiguration

(+)-(1S, 3S, 6S, 8S)-and (?)-(1R, 3R, 6R, 8R)-4, 9-Twistadiene: Synthesis and Absolute Configuration A synthesis and the determination of the absolute configuration of (+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-4, 9-twistadiene ((+)- and (?)- 4 , respectively) is described. Their chiroptical properties are compared with those of saturated twistane ((+)- and (?)- 5 ) as well as with those of the unsaturated and saturated 2, 7-dioxatwistane analogs (+)- and (?)- 9 , and (+)- and (?)- 10 , respectively, which also are compounds of known absolute configurations.     

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.     

Mass spectra of some 2-(4′-butyl-3,′5′-dimethylpyrazol-1′-yl)-6-substituted benzothiazoles

The fragmentation of the title compounds on electron impact has been studied and the major processes interpreted. The base peak invariably appears at [M ? 43]⁺ whose origin from the butyl chain has been traced with the help of metastable ion studies and accurate mass measurements. Loss of methyl cyanide, involving the decomposition of the pyrazole moiety, is observed only from the fragment ions.