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Antioxidative-activity-guided fractionation of extracts of the aerial parts of the title plant yielded the two novel abietanoid diterpenoids 11,20-dihydroxysugiol (=11,12,20-trihydroxyabieta-8,11,13-trien-7-one; 3) and 1,11-epoxy-6,12-dihydroxy-20-norabieta-1(10),5,8,11,13-pentaen-7-one (4) in addition to 11-hydroxysugiol (=12-O-demethylcryptojaponol=11,12-dihydroxyabieta-8,11,13-trien-7-one; 2) and the main constituent carnosolon (=6,20-epoxy-6,11,12-trihydroxyabieta-8,11,13-trien-7-one; 1). The structures were established on the basis of spectroscopic, chiroptic, and X-ray crystallographic evidence.

A series of new esters of lutein (1a) have been prepared with the aim of confirming the structure of lutein via an X-ray crystal-structure analysis. Although well crystallized, only one of the derivatives, the (−)-(1R)-menthyl carbonate (1i) proved to be useful for a complete structure analysis. The same derivative of zeaxanthin (2a) also allowed its crystal structure to be determined. Both analyses represent the first successful X-ray crystal structure analyses of the most important xanthophylls. At the same time, they confirm both the constitution and absolute configuration of 1a and 2a that had been deduced earlier by classical methods.

Incubation of deuteriated precursors in cultures of Flavobacterium produced specifically deuteriated carotenoids. Analysis of these led to several conclusions: i) Lycopene is a direct precursor of β,β-carotene. ii) Its terminal Me groups retain their integrity during cyclization: there is a stereospecific folding of the 1,5-diene. The Me(16,16′) groups of lycopene become the Me(16,16′) of β,β-carotene. Consequently, the folding must follow the C2(E,E) mode. iii) Incorporation of deuterium was sufficiently extensive to permit CD measurements on the isolated β,β-carotene, allowing its centers of chirality to be assigned as (1S,1′S). iv) The same chirality resulted from incorporation of [2H3]mevalonate into zeaxanthin. The syntheses of specifically deuteriated [2H3]GPP, [2H3]FPP, and [2H3]GG are described.

Asymmetric cleavage of ω-azabicyclo[3.n.1]alkan-3-ones was achieved by asymmetric deprotonation at the ‘fork head’ ketone system with Koga’s chiral base and subsequent ozonolysis of the resulting chiral silyl enol ether to give the cis-α,α′-disubstituted piperidine, pyrrolidine and hexahydroazepine, respectively, in high enantiomeric excess.

The transformation of the ‘fork head ketone’ 3b into the corresponding bicyclic lactone 13 via the Beckmann followed by the Huisgen–White rearrangement is described. Application of the method to a homochiral 2-etyl-substituted bicyclic ketone (+)-3dα gave efficiently (–)-dihydropalustramic acid (–)-2a, a degradation product from the alkaloid palustrine 1, in good optical yield.

(6R,9′Z)-Neoxanthin: Synthesis, Physical Properties, Spectra, and Calculations of Its Conformation in Solution The synthesis of pure and crystalline (9′Z)-neoxanthin (6) is described. MnO2 Oxidation of (9Z)-C15-alcohol 7 at room temperature produces a mixture 8/9 of (9Z)- and (9E)-aldehydes. Predominant formation of the required (9Z)-aldehyde 8 is achieved by performing the oxidation at − 10°. Condensation of 8 with the mono-Li salt of the symmetrical C10-diphosphonate 10 gave the (9Z)-C25-monophosphonate 11. The Wittig-Horner condensation of 10 with the allenic C15-aldehyde 1b, under selected conditions allows the preparation of pure and crystalline (9′Z)-15,15′-didehydroneoxanthin (12) and, after subsequent semireduction, of crystalline (15Z,9′Z)-neoxanthin (13). Thermal isomerisation of a AcOEt solution of 13 at 95° yields preferentially (9′Z)-neoxanthin (6). Our crystalline sample shows the highest ϵ-values in the UV/VIS spectra ever recorded. The CD spectra display a pronounced similarity with those of corresponding violaxanthin isomers. In contrast to the (all-E)-isomer 5, (9′Z)-neoxanthin undergoes very little isomerisation when heated to its melting point. For comparison purposes, a crystalline probe of 6 is also isolated from lawn mowings. Extensive 1H-and 13C-NMR investigations at 600 MHz of a (D6)benzene solution using 2D-experiments such as COSY, TOCSY, ROESY, HMBC, and HMQC techniques permit the unambiguous assignment of all signals. Force-field calculations of a model system of 6 indicate the presence of several interconverting conformers of the violaxanthin end group, 66% of which possess a pseudoequatorial and 34% a pseudoaxial OHC(3′). The torsion angle (ω1) around the C(6′)C(7′) bond, known to be of prime importance for the shape of the CD spectra, varies with values of 87° for 55% and 263° for 45% of the molecules. Therefore, the molecules clearly display a preference for the ‘syn’-position of the C(7′)C(8′) bond and the epoxy group. Unexpectedly, the double bonds of C(7′)C(8′) and C(9′)C(10′) are not coplanar. The deviation amounts to ± 20°, both in the ‘syn’ - and the ‘anti’-conformation.

Synthesis of (6R, all-E)-Neoxanthin and Related Allenic Carotenoids We present the first synthesis of enantiomerically pure neoxanthin (1) by a Wittig-Horner condensation between the ylide from the novel diethyl 12′-apo-15, 15′-didehydroviolaxanthin-12′-phosphonate (35) and the allenic C15-aldehyde 31 (Scheme 4) via the crystalline 15, 15′-didehydroneoxanthin (36; 70% yield). After partial hydrogenation of the triple bond of 36 and isomerisation of the (15Z)-intermediate 37, neoxanthin (1) was obtained in good yield. Similar syntheses gave (15Z, 9′Z)-neoxanthin (45; Scheme 5) and (9Z)-15, 15′-didehydroneoxanthin (47; Scheme 6). Comparison of the physical data of synthetic 1 with those of a freshly isolated sample of neoxanthin from the flowers of Trollius europaeus confirmed their identity. The unusually low melting point of 1 is caused by a very easy thermal isomerisation into a mixture of the neochromes 4 and 5 (Scheme 1). Such a thermal rearrangement is not observed with 15, 15′-didehydroneoxanthin (36). To explain this, we assume a zwitterionic excited state of the allenic group that induces the rearrangement of the violaxanthin end group into the furanoid epoxide (Scheme 7).

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.

In this article we present a survey of the pigments found in the flowers and fruits of old and modern varieties of roses. The yellow colors are produced by carotenoids, the reds by anthocyanins, and the modern oranges by a mixture of the two. The great structural diversity of the carotenoids contrasts with a surprisingly small number of anthocyanins. For the carotenoids found in roses, a clear correspondence exists between the structure and the breeding partners used; the old yellow roses, which arose from crosses with Chinese varieties, mainly contain carotenoids from early stages in the biosynthesis, while in the modern yellow roses, which are descended from Central Asian foetida types, hydroxylations, epoxidations, and epoxide transformations readily occur. A recently elucidated carotenoid degradation sequence follows the scheme C40 → C13 + C27 → C13 + C14. The C13 compounds are odoriferous substances that contribute to the scent of roses. In the physiological pH region, copigmentation with flavonol glycosides is crucial for stabilization of the anthocyanin chromophores. Many roses, including the “apothecary's rose”, which was once used medicinally, contain large amounts of strongly astringent ellagitannins, monosaccharide esters of gallic acid.

Wir geben einen Uberblick Uber Farbstoffe aus Bluten und Fruchten alter und moderner Rosen und konnen zeigen, das die gelben Farben der Rosen durch Carotinoide, die roten durch Anthocyanine und die modernen orangeroten durch ein Gemisch beider erzeugt werden. Der grosen strukturellen Vielfalt bei Carotinoiden steht eine uberraschend geringe bei Anthocyaninen gegenuber. Bei den Carotinoiden aus Rosenbluten ist der Zusammenhang zwischen Struktur und verwendetem Kreuzungspartner evident: alte gelbe Rosen, entstanden durch Einkreuzen von chinesischen Sorten, besitzen vorwiegend Carotinoide aus fruhen Biogenesestufen, neuere gelbe Rosen mit Abstammung von mittelasiatischen Foetida-Typen fuhren dagegen weiterfuhrende Hydroxylierungen, Epoxidierungen und Epoxidtransformationen mit Leichtigkeit aus. Ein neuer Carotinoidabbau verlauft nach dem Schema C40 C13 + C27 C13 + C14, wobei die C13-Verbindungen Duftstoffe sind. Fur die Stabilisierung der Anthocyanin-Chromophore im physiologischen pH-Bereich ist die Copigmentierung mit Flavonolglycosiden wesentlich. Viele Rosenbluten, so auch diejenigen der fruher medizinisch verwendeten Apothekerrose, enthalten grose Mengen von stark adstringierend wirkenden Ellagitanninen, die Ester aus Monosacchariden und Gallussaure sind.

Synthesis of Enantiomerically Pure Mimulaxanthin and of Its (9Z,9′Z)- and (15Z)Isomers We present the details of a synthesis of optically active, enantiomerically pure stereoisomers of mimulaxanthin (=(3s,5R,6R,3′S,5′R,6′R)-6,7,6′,7′-tetradehydro-5,6,5′,6′-tetrahydro-β,β-carotin-3,5,3′,5′-tetrol) either as free alcohols 1a and 24a or as their crystalline (t-Bu)Me2Si ethers 1b and 24b. Grasshopper ketone 2a, a presumed synthon, unexpectedly showed a very sluggish reaction with Wittig-Horner reagents. Upon heating with the ylide of ester phosphonates, an addition across the allenic bond occurred. On the contrary, a slow but normal 1,2-addition took place with the ylide from (cyanomethyl)phosphonate but, unexpectedly, with concomitant inversion at the chiral axis. So a mixture of(6R,6S,9E,9Z)-isomers 6–9 was produced {(Scheme 1). However, a fast and very clean 1,2-addition occurred with the ethynyl ketone 12 to yield the esters 13 and 14 (Scheme 2). DIBAH reduction of the separated stereoisomers gave the allenic alcohols 15 and 16 in high yield. Mild oxidation to the aldehydes 17 and 18 followed by their condensation with the acetylenic C10-bis-ylide 19 led to the stereoisomeric 15,15′-didehydromimulaxanthins 20 and 22, respectively (Schemes 3 and 4). Mimulaxanthins 1 and 24 were prepared by partial hydrogenation of 20 and 22 followed by a thermal (Z/E)-isomerization. As expected, the mimulaxanthins exhibit very weak CD curves, obviously caused by the allenic bond that insulates the chiral centers in the end group from the chromophor. On the contrary, some of the C15-allenic synthons showed not only fairly strong CD effects but also a split CD curve which, in our interpretation, results from an exciton coupling between the allene and the C(9)C(10) bond. We postulate a rotation around the C(8)C(9) bond, presumably caused by an intramolecular H-bond in 16 or by a dipol interaction between the polarized double bonds in 6, 7, 8, and 17.

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.

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-e,e-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 e,e-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.

Neoflor and 6-Epineoflor from Flowers of Trollius europaeus; Highfield 1H-NMR Spectra of (all-E)-Neoxanthin and (9′Z)-Neoxanthin Re-isolation of the very polar carotenoids from flowers of the title plant furnished two epimeric pentahydroxy compounds. Based on spectroscopical and chiroptical arguments and by chemical correlation with neoxanthin, their structures were established as 11 (proposed name neoflor) and 12 (6-epineoflor), Decoupling experiments and COSY-2D-1H-NMR spectra allowed a complete assignement of the vinyl protons of the two isomers, and furthermore, for the first time, also of those of (all-E)-neoxanthin and (9′Z)-neoxanthin.

A Further, Now Successful Search for 3′-Epilutein in Plants The 3′-epilutein, an extremely rare carotenoid, found till now in only one plant, was detected in anthers of flowers of several roses and in those of peonies.

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.

Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related Compounds Starting from our previously described synthon 1, the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4-(2′,4′-dihydroxy-2′,6′,6′-trimethylcyclohexylidene)but-3-en-2-ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.

Structure of the Valenciaxanthins and Valenciachromes Valenciaxanthin, a carotenoid first isolated from Californian Valencia orange juice in 1952/1954 by American scientists, was re-isolated from fresh Spanish ‘Navelinas’ and shown, by spectroscopical and chiroptical examination, to have the unexpected (9Z)-10′-apo-11′,12′-dihydroviolaxantin-10′-ol structure 6. A further, very minor component represents the (all-E)-structure 7. Therefore, the Valenciachromes are the furanoid rearrangement products of 6 and 7 and, thus, stereoisomers of the 10′-apo-11′,12′-dihydroauroxanthiiv 10′-ols 8. Valenciaxanthin represents a modification of the common cleavage of carotenoids in higher plants according to the scheme C40 C27 + C13, insofar as the reduction step not only includes the aldehyde function but also the subsequent conjugated double bond.

Synthesis of Plectranthons, Diterpenoid Phenanthrene-1,4-diones The following phenanthrene-1,4-diones have been synthesized by using the photocyclization of the corresponding highly substituted stilbenes as the key step: 3-hydroxy-5,7,8-trimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione (1), (RS)-, (R)-, and (S)-2-[3-hydroxy-5,7,8-trimethyl-1,4-dioxophenanthren-2-yl]-1-methylethyl acetate (2, 31, and 32, resp.), 3-hydroxy-7,8-dimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione (3), 3-hydroxy-7,8,10-tri-methyl-2-(prop-2-enyl)phenanthrene-1,4-dione (4), 5,7,8-trimethyl-2-(prop-2-enyl)phenanthrene-1,4-dione (17), and 3-hydroxy-2-methylphenanthrene-1,4-dione (42). The quinones 1 and 3 proved to be identical with the recently isolated plectranthons A and C. Compounds 2, 31, and 32 exhibited the same UV/VIS, IR, 1H-NMR and mass spectra as natural plectranthon B, but had different melting points. This might be due either to crystal modifications or to diastereoisomerism caused by the helical structure of the phenanthrene-1,4-dione skeleton. The spectral data of synthetic 4 were not compatible with those of natural plectranthon D for which structure 4 had been proposed based mainly on 1H-NMR arguments concerning the chemical shifts of HC(9) and HC(10) in 1–3. Extensive 1H-NMR investigations have now revealed that the currently stated assignments of the HC(9)/ HC(10) AB system have to be reversed for highly substituted phenanthrene-1,4-diones: in the model compounds 2-methylphenanthrene-1,4-dione (41) and 2, HC(10) resonates al lower field as expected (peri-position), whereas in the highly substituted congeners 1, 2, 3, 31, and 32, HC(9) is shifted paramagnetically, a fact which had lead to the erroneous assignment of structure 4 for natural plectranthon D.

The transformation of the «fork head ketone» (1) into the corresponding bicyclic lactone (4) via the Beckmann followed by the Huisgen-White Rearrangement is described. An α-ethyl-substituted bicyclic ketone (5) was converted efficiently to dihydropalustramic acid (6), a degradation product from the alkaloid palustrine

Leaf-gland Pigments: Coleons S and T from Plectranthus caninus ROTH(Labiatae), New Hydroquinones of the Abietane Series with a Diosphenol/trans-A/B-6,7-Diketone Structure. Coleons S and T were isolated from the more polar fractions from extracts of the above mentioned plant. Coleon S, C20H26O6, has been shown to have structure 1a, and coleon T, C20H26O6, structure 2.

Synthesis of (-)-(R)-4-Hydroxy-β-ionone and (-)-(5 R, 6 S)-5-Hydroxy-4,5-dihydro-α-ionone aus (-)-(S)-α-Ionone The absolute configuration of the chiral 4-hydroxy-β-ionones and 5-hydroxy-4,5-dihydro-α-ionones has been determined by chemical connection with (-)-(S)-α-ionone i.e. by stereoselective epoxidation of the latter, followed by base catalyzed opening of the epoxide as well as by its hydride reduction.

Partial Syntheses and Reactions of Abietanoid Derivatives (Lanugones) from Plectranthus lanuginosus and of Related Compounds Interconversions by partial syntheses of several lanugones establish their absolute configuration at C(15). Unexpected reactions exemplify the unique reactivity of these abietanoic diterpenes, - Lanugone O (4) was prepared in several steps from (15S)-coleon C (8a; Scheme 2) thus establishing its (15S)-configuration. One of the intermediates, the 12-O-acetyl-6-oxoroyleanone 12, through acetyl-migration sets up an equilibrium with the vinylogous quinone 13 (Scheme 3). - The chirality at C(15) in the dihydrofuran moiety of lanugone Q (16) was proven by acid-catalyzed conversion of lanugone O (4) to 16. - Instead of the usual nucleophilic attack shown by quinomethanes, lanugone L (1) is electrophilically substituted at C(7) by acetic anhydride/pyridine (Scheme 1). - In a homosigmatropic [1,5]-H-shift, lanugone G (17) in solution is converted to the corresponding allyl substituted royleanone 18 (Scheme 4). - Methanolysis of lanugone J (19) leads to the expected royleanone 20 having the 2-methoxypropyl side chain (Scheme 5). Similar reactions were found in acetolytic reactions. However, treatment-of spirocoleons with SOCl2/DMF produces mainly 12-deoxyroyleanones with allyl- and 2-chloropropyl groups, i. e. 1926 and 27; 28 29. The possible natural occurrence of these compounds is emphasized.

Activated Quinones: Regiospecific Syntheses of Substituted Dibenzo [b, d]pyran-6-ones and Benzo[b]naphtho [d]pyran-6-ones The reaction of 2-methoxycarbonyl-1, 4-benzoquinone (1) with substituted phenols leads in an acid-catalyzed, regiospecific way to substituted dibenzo [b, d]-pyran-6-ones (compounds 3 and 6). The cycloaddition of 1,3-butadiene to the latter yields compounds 7. Tautomerisation of 7 and oxidation gives the benzo[b]-naphtho[d]pyran-6-ones 8 and 10, respectively.

Synthesis of Enantiomerically Pure Apoviolaxanthinoic Acids, Apoviolaxanthinols, and Apoviolaxanthinals (Including Persicaxanthin, Sinensiaxanthin, and β-Citraurin Epoxide) and of their Furanoid Rearrangement Products Starting from (1′S,2′R,4′S,2E,4E)-5-(1′,2′-epoxy-4′-hydroxy-2′,6′,6′-trimethylcyclohexy1)-3-methy1-2,4-pentadienal (3), a recently described synthon [6], a full range of C20-, C25-, C27-, and C30-polyenic acids, alcohols, and aldehydes and their (8R)- and (8S)-diastereoisomeric furanoid rearrangement products was prepared. The synthetic C25-alcohols proved to be identical with persicaxanthin (= 12′-apoviolaxanthin-12′-ol) and perisicachromes (= 12′-apoauroxanthin-12′-ols) and the C27-alcohols analogously with sinensiaxanthin and sinensiachromes. A correlation between the sign of the Cotton effects in the CD spectra of 5,6-and 5,8-epoxides and their configuration at C(6) and C(8), respectively, was established.

The Diastereomeric Aurochromes: Their Synthesis, Analysis and Chiroptical Properties (all-E)-Aurochrome (5,8:5′,8′-diepoxy-5,8,5′,8′-tetrahydro-β,β-carotene; 1) has two pairs of constitutionally identical chiral centres and, therefore, is expected to exist in four pairs of enantiomers and two meso-forms. Using starting materials with well-defined configuration, we performed the syntheses of the following pure aurochromes: (5R,8R,5′R,8′R)-aurochrome (2) and its racemate, Meso-(5R,8R,5′S,8′S)-aurochrome (3), (5 R,8 S,5′ R,8′ S)-aurochrome (4) and its racemate, meso-(5R,8S,5′S,8′R)-aurochrome (5), (5R,8R,5′R,8′S)-aurochrome (6) and its racemate. The (5RS,8RS,5′SR,8′RS)-aurochrome (7) was detected chromatographically, using a HPLC system that allows clean separation of the four racemic- (or optically active) and the two meso-aurochromes. The optically active autochromes 2 and 4 exhibit non-conservative CD spectra with strong Cotton effects of opposite but not mirror-like tracings. Solutions of aurochromes in CHCl3, in the presence of HCl, undergo epimerization at C(8). Those epimers with CH3trans to C(9) slightly predominate under equilibrium conditions. Deprotonation of the phosphonate (±)-14 with strong base causes isomerization at the terminal oxirane into a dihydrofuran. This reaction allowed convenient syntheses of the diastereoisomeric aurochromes (±)-2, 3, (±)-4, 5, (±)-6, and (±)-7 and of (5RS, 8RS)- and (5RS, 8SR)-12′-apo-aurochrome-12′-als (21 and 22, respectively).

Structure and properties of 5-epi-flavoxanthin and 5-epi-chrysanthemaxanthin The absolute configurations of 5-epi-flavoxanthin (6) and 5-epi-chrysanthemaxanthin (7) prepared by acid catalysed rearrangement of semi-synthetic lutein epoxide 5 are shown to be (3S, 5S, 8R, 3′R, 6′R) and (3S, 5S, 8S, 3′R, 6′R), respectively. Contrary to published data [5] the relationship of the polyene chain and H3(18) on the dihydrofurane ring is cis for the pair of stereoisomers having a Δδ = δ (HC(7)) − δ (HC(8)) = 0,22 ppm and 3J ≡ 0. These conclusions are in full accord with the chiroptical data.

Carotenoids from Hips of Rosa pomifera: Discovery of (5Z)-Neurosporene; Synthesis of (3R, 15Z)-Rubixanthin Extensive chromatographic separations of the mixture of carotenoids from ripe hips of R. pomifera have led to the identification of 43 individual compounds, namely (Scheme 2): (15 Z)-phytoene (1), (15 Z)-phytofluene (2), all-(E)-phytofluene (2a), ξ-carotene (3), two mono-(Z)-ξ-carotenes (3a and 3b), (6 R)-ϵ, ψ-carotene (4), a mono-(Z)-ϵ, ψ-carotene (4a), β, ψ-carotene (5), a mono-(Z)-β, ψ-carotene (5a), neurosporene (6), (5 Z)-neurosporene (6a), a mono-(Z)-neurosporene (6b), lycopene (7), five (Z)-lycopenes (7a–7e), β, β-carotene (8), two mono-(Z)-β, β-carotenes (probably (9 Z)-β, β-carotene (8a) and (13 Z)-β, β-carotene (8b)), β-cryptoxanthin (9), three (Z)-β-cryptoxanthins (9a–9c), rubixanthin (10), (5′ Z)-rubixanthin (=gazaniaxanthin; 10a), (9′ Z)-rubixanthin (10b), (13′ Z)- and (13 Z)-rubixanthin (10c and 10d, resp.), (5′ Z, 13′ Z)- or (5′ Z, 13 Z)-rubixanthin (10e), lutein (11), zeaxanthin (12), (13 Z)-zeaxanthin (12b), a mono-(Z)-zeaxanthin (probably (9 Z)-zeaxanthin (12a)), (8 R)-mutatoxanthin (13), (8 S)-mutatoxanthin (14), neoxanthin (15), (8′ R)-neochrome (16), (8′ S)-neochrome (17), a tetrahydroxycarotenoid (18?), a tetrahydroxy-epoxy-carotenoid (19?), and a trihydroxycarotenoid of unknown structure. Rubixanthin (10) and (5′ Z)-rubixanthin (10a) can easily be distinguished by HPLC. separation and CD. spectra at low temperature. The synthesis of (3 R, 15 Z)-rubixanthin (29) is described. The isolation of (5 Z)-neurosporene (6a) supports the hypothesis that the ϵ-end group arises by enzymatic cyclization of precursors having a (5 Z)- or (5′ Z)-configuration.

Two Optically Active Luteochromes: Preparation, Spectra and Chiroptical and Chromatographic Properties Selective rearrangement of (5R,6S,5′ R,6′S)-5,6:5′, 6′ -diepoxy-5,6,5′, 6′ -tetrahydro- β,β -carotene with the aid ofan ethereal solution of malonic acid leads to the mixture of the C(8′)-epimeric luteochromes. HPLC separation gave the pure isomers. This is the first report on th preparation of optically active luteochromes.

Isolation and Structure Elucidation of 36 Diterpenoids from Leaf-Glands of Plectranthus edulis (VATKE) T.T. AYE Analysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A (40), a 5(43) abeo-abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7-dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10-seco-abietanoids), and deacetyledulon A. The known coleon-A-lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ-enollactol 44, combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H-5-oxaaceanthrylen skeleton of edulon A.

Leaf-gland Pigments: 6-Novel p-Quinomethanes of the Abietane Series from Plectranthus parviflorus WILLD The above mentioned plant accumulates in its red coloured leaf-glands a complex mixture of strongly dehydrogenated abietanols. They were separated (with difficulties) to yield 6 novel compounds. Spectroscopic and chiroptic data show them to be esters of either 11, 19-dihydroxy- or 2 α, 11-dihydroxy-abieta-5, 7, 9 (11), 13-tetraen-12-one 2a and 3a, respectively. Specifically, the 19-O-p-hydroxybenzoate (2d) parvifloron C, the 19-O-vanilloate (2c) parvifloron B, the 19-O-p-hydroxy-benzoate (2d) parvifloron C, the 19-O-3′,4′-dihydroxybenzoate (2e) parvifloron E, the 2 α-O-p-hydroxybenzoate (3b) parvifloron D, and the 2 α-O-3′,4′-dihydroxy-benzoate (3c) parvifloron F. Reduction by LiAlH4 splits the ester function and reduces the p-quinomethane to a colourless pyrocatechol derivative which, by air oxidation, regenerates the red p-quinomethane system of 2a and 3a.

Horminone, taxoquinone and other royleanones, obtained from two Abyssinian Plectranthus species (Labiatae). From the coloured glands on the leaves of two botanically unclassified Plectranthus sp. from Abyssinia, a series of royleanones has been isolated, namely royleanone (1) and 6,7-dehydroroyleanone (2) from one species, and 6,7-dehydroroyleanone, horminone (3), taxoquinone (4), 6β, 7α-dihydroxyroyleanone (5), 7α-acetoxy-6β-hydroxyroyleanone (6) and 7-oxoroyleanone (7) respectively, from the other.

Synthesis of [16,16,16,16′,16′,16′ 2H6]Lycopene Lycopene having at both ends the deuteriated methyl groups trans to the chain has been synthesized for further biochemical experiments aimed to elucidate the stereochemistry of the cyclization step. Incidentally a gas-chromatographic separation of the isotopisomers 1 and 2g has been observed.

Activated quinones: substitution reactions by methoxy-carbonyl-1,4-benzoquinone of azulenes, benzofuran and indoles; regiospecific syntheses of polymethoxy-fluorenones; a new synthesis of the 2,6-dihydro-naphtho[1,2,3-cd]indol-6-one system. We present new electrophilic substitution reactions of azulenes and 5-membered heterocyclics by methoxy-carbonyl-1,4-benzoquinone. Hydroquinones 3a and 5 are prepared from azulene, and 3b from guaiazulene (see Scheme 1). Benzofuran undergoes α- and β-substitution (hydroquinones 910) (see Scheme 2). Only β-substitution is observed with indole (hydroquinone 20) (see Scheme 4). After methylation, saponification and intramolecular acylation of the substituted indoles 22c, 22d, derivatives of 2,6-dihydro-naphtho[1,2,3-cd]indol-6-one have been obtained. Spectral data prove the presence of the methylidenequinone tautomer. By protonation or alkylation at the carbonyl group of 23, the violet, highly delocalized 16π-electron systems 25 are generated. Analogously, polymethoxy-fluorenones have been prepared from methoxylated diphenylquinones 15 (see Scheme 3). They also are transformed by protonation and alkylation to the highly coloured and delocalized 12 π-electron systems 18. By contrast, anthracene is not substituted by methoxycarbonyl-1,4-benzoquinone, but undergoes cycloaddition to the triptycene derivative 1 (see Scheme 1). A summary is presented of previously described reactions of activated quinones.

Partial Synthesis of Grandidones A, 7-Epi-A, B, 7-Epi-B, C, D and 7-Epi-D, from 14-Hydroxytaxodione Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fetizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fetizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fetizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved. Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fetizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.

Diazo coupling of 3,4-dimethoxyfuran with aryl diazonium ions 3,4-Dimethoxyfuran (1) easily reacts with aryl diazonium chloride in aqueous pyridine in an expected 1, 4-addition reaction. From the isolable primary addition product pyridine is displaced by alcohols, phenols or thiols to yield 4-alkoxy- or 4-phenoxy- or 4-thiophenoxy-derivatives of 2,3-dimethoxy-2-buten-4-olide (3). Attempts to convert them into azo compounds by a base catalysed 1, 6-elimination reaction failed. Oxidation of 3a and 3c with DDQ results in the formation of the mono p-nitrophenylhydrazone of 3, 4-dimethoxymaleic acid anhydride. On the other hand, the thiophenoxy compound 3g is smoothly converted by MnO2 into the authentic furan-2-azobenzene derivative 5.