Drüsenfarbstoffe aus Labiaten: Die polaren Diterpenoide aus Plectranthus argentatus S. T. BLAKE

Polar Diterpenoids from Leaf-Glands of Plectranthus argentatus S. T. B_LAKE From the red leaf-glands of the Australian Plectranthus argentatus the following novel diterpenoids were isolated: coleon-U-quinone ( 1 ), 8α,9α-epoxycoleon-U-quinone ( 3 ), 6β-formyloxy-7α-hydroxyroyleanone ( 7 ), and 5,6-dihydrocoleon U ( 10 ), besides the already known compounds 6β, 7α-dihydroxyroyleanone ( 4 ), 7α-acetoxy-6β-hydroxyroyleanone ( 5 ), and 7α-formyloxy-6β-hydroxyroyleanone ( 6 ). Epoxydation of 1 by perborate led in 32% yield to the epoxyquinone 3 .     

Plectranthone A,B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae)

Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae) The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu₂, Rwanda, are proposed: plectranthon A ( 1 ; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B ( 2 ; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C ( 3 ; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D ( 4 ; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione ( 11 ), a compound very similar to 1–4 , was prepared by a Wagner-Meerwein, rearrangement of coleon E (⁵). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C₂₀-phenanthrenes of diterpenoid origin.     

Struktur von Edulon A

Structure of Edulon A Based on new chemical reactions and an X-ray analysis of the derived camphanic ester 2e , edulon A has been shown to have the structure 2a , i.e. (10bS, 1′S)-8-(2′-acetoxy-1′-methylethyl)-2,4,6, 10b-tetrahydro-7,9, 10-trihydroxy-3, 10b-dimethyl-1H-5-oxaaceanthrylene-4,6-dione. Therefore, it is not a 2H-1-oxapyrene as previously assumed, but a derivative of the novel 4H-5-oxaaceanthrylene skeleton.     

Coleone C,D, I,I′ aus einer madegassischen Plectranthus sp. nov. Interkonversion von cis- und trans-A/B-6,7-Diketoditerpenen

Coleons C, D, I, I′, obtained from a Madagascan Plectranthus sp. nov.. Interconversion of cis- and trans-A/B-6,7-Diketoditerpenes. Fairly large amounts of Coleons C and D, as well as Coleons I and I′ (3-O-formyl derivative of Coleon I) can bc isolated from the orange glands of an unclassified North Madagascan Plectranthus sp. A reversible transformation of cis- and trans-A/B-6,7-dioxo-abietane via its diosphenol has been achieved for the first time. CD.-Spectra of these compounds are presented. Hydrogenolysis of Coleon D leads to 6β,16-dihydroxy-royleanone.     

Neue Diterpenoide aus Blattdrüsen einer Plectranthus sp. aus Rwanda

Novel Diterpenoids from Leaf-Glands of a Plectranthus sp. from Rwanda More than 20 highly modified abietanoid compounds belonging to 6,7-dioxocoleons, serveral kinds of royleanones, spirocoleons, extended quinones, quinone methides, and 1,4-phenanthraquinones have been isolated from a Plectranthus sp. from the borders of Lake Kiwu (Rwanda). The structure of plectranthon A ( 1 ), a 5,7,8-trimethyl-1,4-phenanthraquinone, has been confirmed by an X-ray analysis of its p-bromobenzoate. It is twisted around the C(4)–C(5) moiety; this fact renders the molecule chiral. Notable features of the hydroxylation pattern in all of the isolated compounds are: (a) a predominant hydroxylation at C(16) (abietan numbering) leading to the (15S)-configuration of the 2-hydroxy-l-methylethyl side-chain and to the (13S, 15R)-configuration of the derived spirocyclopropanes and to the derived (S)-2-hydroxypropyl side-chain; (b) the 6β,7α-dihydroxylation which, together with further hydroxylations at C(3) and/or C(2), are considered as a prerequisite for the formation of the conjugated system extending over rings A, B and C (e.g. in the coleons E and F), hence allowing a complete aromatization of the basic ring skeleton. The reasons for these extensive dehydrogenation and oxygenation reactions that cost the plant a great many of oxidation equivalents are not clear. Presumably, these modifying reactions preceed the degradation of the ring system.     

Synthese von Alkylphenolen und -pyrocatecholen aus Plectranthus albidus (Labiatae)

Synthesis of Alkylphenols and -catechols from Plectranthus albidus (Labiatae) In the preceding paper, we described the isolation and structure elucidation of a series of even-numbered phenol- or pyrocatechol-derived 1-arylalkane-5-ones. To establish the assigned structures unambiguously and to have larger quantities available for physiological testing, the following compounds were prepared: in the alkylphenol series, 1-(4′-hydroxyphenyl)tetradecan-5-one ( 2a ), 1-(4′-hydroxyphenyl)hexadecan-5-one ( 2b ), and 1-(4′-hydroxyphenyl)octadecan-5-one ( 2c ); in the alkylcatechol series, 1-(3′,4′-dihydroxyphenyl)decan-5-one ( 3a ; not isolated as a natural compound), 1-(3′,4′-dihydroxyphenyl)dodecan-5-one ( 3b ), 1-(3′,4′-dihydroxyphenyl)tetradecan-5-one ( 3c ), 1-(3′,4′-dihydroxyphenyl)hexadecan-5-one ( 3d ), 1-(3′,4′-dihydroxyphenyl)octadecan-5-one ( 3e ), and 1-(3′,4′-dihydroxyphenyl)icosan-5-one ( 3f ); in the alkenylphenol series, (Z)-1-(4′-hydroxyphenyl)octadec-13-en-5-one ( 4a ) and (E)-1-(4′-hydroxyphenyl)octadec-13-en-5-one ( 4b ); in the alkenylcatechol series, (E,E)-1-(3′,4′-dihydroxyphenyl)deca-1,3-dien-5-one ( 1 ) and (Z)-1-(3′,4′-dihydroxyphenyl)octadec-13-en-5-one ( 5 ). All compounds proved to be identical with the previously assigned structures. Compound 1 was synthesized by regioselective aldol condensation of heptan-2-one with (E)-1-(3′,4′-dimethoxyphenyl)prop-2-enal ( 6d ; Scheme 1), the phenols 2a–c and the catechols 3a–f by addition of the corresponding alkyl Grignard reagent to 5-(4′-methoxyphenyl)- or 5-(3′,4′-dimethoxyphenyl)pentanal ( 17c and 18c , resp.; Scheme 4), and the olefins 4a, 4b and 5 from 17c or 18c via the 9-O-silyl-protected 13-(4′-methoxyphenyl)- or 13-(3′,4′-dimethoxyphenyl)tridecanals ( 26 and 27 , resp.) and Wittig olefination as the key steps (Scheme 5).     

Isolierung und Struktur von langkettigen Alkylphenolen und -pyrocatecholen aus Plectranthus albidus (Labiatae)

Isolation and Structure of Long-Chain Alkylphenols and -catechols from Plectranthus albidus (Labiatae) From the title plant, a series of even-numbered long-chain, phenol- or pyrocatechol-derived 1-arylalkan-5-ones was isolated by classical chromatography and preparative reversed phase HPLC. By chemical and spectroscopic methods, including coupled chromatographic techniques (GC/MS/FT-IR, HPLC/MS), their structures were established to be 1-(4′-hydroxyphenyl)tetradecan-5-one ( 2a ), 1-(4′-hydroxyphenyl)hexadecan-5-one ( 2b ), 1-(4′-hydroxyphenyl)octadecan-5-one ( 2c ), and (Z)-1-(4′-hydroxyphenyl)octadec-13-en-5-one ( 2d ); (E,E)-1-(3′,4′-dihydroxyphenyl)deca-1,3-dien-5-one ( 1a ), 1-(3′,4′-dihydroxyphenyl)dodecan-5-one ( 3a ), 1-(3′,4′-dihydroxyphenyl)-tetradecan-5-one ( 3b ), 1-(3′,4′-dihydroxyphenyl)hexadecan-5-one ( 3c ), 1-(3′,4′-dihydroxyphenyl)octadecan-5-one ( 3d ), 1-(3′,4′-dihydroxyphenyl)icosan-5-one ( 3e ), and (Z)-1-(3′,4′-dihydroxyphenyl)octadec-13-en-5-one ( 3f ). In vitro, the compounds show significant antioxidant activity, the inhibitory concentration of the most potent one, 1a , being slightly lower than for 2-(tert-butyl)-4-methoxyphenol (BHA) and 2,6-di(tert-butyl)-4-methylphenol (BHT) in the Fe²⁺-catalysed autooxidation of linoleic acid, whereas the acitivities of phenols 2a–d are in the same order of magnitude as α-tocopherol.     

Drüsenfarbstoffe aus tropischen Labiaten: Parviflorone aus Plectranthus strigosus BENTH.

Red-Coloured Abietanoids from Leaf-Glands of Plectranthus strigosus BENTH . Chromatographic examination of the red-coloured diterpenoids from the South-African title plant yielded the following compounds: parviflorone A(1) , parviflorone B (2) , parviflorone C(3) , parviflorone E (4) parviflorone D (5) , parviflorone F (6) , parviflorone G (7) , and parviflorone H (8) . Compounds 7 and 8 represent new variants of these quinone methides.     

Diterpenoide Drüsenfarbstoffe aus Labiaten: 3β-Acetoxyfuerstion,Nilgherron A und Nilgherron B,neue Chinomethane aus Plectranthus nilgherricus BENTH.; absolute Konfiguration von Fuerstion

Leaf-gland Pigments: 3β-Acetoxyfuerstione, Nilgherron A and Nilgherron B, New Quinomethanes from Plectranthus nilgherricus BENTH . (Labiatae); Absolute Configuration of Fuerstione We have isolated from leaf-glands of the above mentioned plant the following deeply coloured quino-methane derivatives: (1) traces of the already known fuerstione ( 1a ); 11,15-dihydroxy-5,7,9 (11), 13-abietatetraen-12-one; (2) the new 3β-acetoxy-fuerstione ( 1b ); (3) nilgherron A ( 5a , I or II), a new dimeric diterpenoid quinomethane, C₄₀H₅₂O₇, formed in the plant obviously by cycloaddition of the o-quinone 8 (9aS, 11R)-11 -hydroxy-2-(1-hydroxy-1-methylethyl-9,9-dimethyl-3,4,7,8,9,9a,10,11- octahydro-5H-dibenzo [a, d]cycloheptene-3,4-dione) with fuerstione; (4) nilgherron B ( 5b , I or II), C₄₂H₅₄O₉, likewise a new compound, formed by the same type of cycloaddition (heterodiene synthesis) of 8 with 3β-acetoxyfuerstione. On the basis of ¹H-NMR. shift arguments structure I is slightly preferred to II for 5a and 5b . Model experiments have shown the easy formation of the dihydrodioxin ring by reaction of an o-benzoquinone with p-quinomethanes. The absolute configuration of fuerstione and 3β-acetoxyfuerstione has been determined by chiroptical methods.     

Chemical Constituents of the Endophytic Fungus Phomopsis sp. A240 Isolated from Taxus chinensis var. mairei

A new sesquiterpene, eremophil‐9‐ene‐11,12,13‐triol ( 1 ), a new oxazole, 4‐(2‐hydroxyethyl)‐5‐methyloxazole ( 2 ), and the two known lactones, 5′‐hydroxyalternariol ( 3 ) and alternariol ( 4 ), were isolated from the extract of Phomopsis sp. A240, an endophytic fungus isolated from the bark of Taxus chinensis var. mairei. The structures of the isolated compounds were determined by analyses of their spectroscopic data, as well as by comparison with literature reports. The isolated compounds were evaluated for their cytotoxic and antioxidant activities.     

Chemical Constituents of a Formosan Soft Coral Sinularia sp.

A new marine sterol 7β-hydroperoxy-24-methylenecholesterol ( 1 ) along with five known compounds sarcophytol A ( 2 ), (Z)-N-[2-(4-hydroxyphenyl)ethyl]-3-methyldodec-2-enamide ( 3 ), 5α,7αH-eduesm-11(13)en-4α-ol ( 4 ), 24-methylenecholesterol ( 5 ) and 1β-hydroxy-α-cyperone ( 6 ) have been isolated from a Formosan soft coral Sinularia sp. The structures of the above compounds were determined by spectral analyses. Cytotoxicity of compounds 1–6 toward various cancer cell lines also is reported.     

1H and 13C NMR assignments of eight nitrogen containing compounds from Nocardia alba sp.nov (YIM 30243T)

An unprecedented new natural product named nocarsin A (1), 5H‐4a,6,7a‐triazacyclopenta[cd]indene‐5,7(6H)‐dione (1), together with seven known compounds lumichrome (2), cyclo (L ‐Leu‐L ‐Tyr) (3), cyclo (L ‐Ala‐L ‐Ile) (4), cyclo (L ‐Ala‐L ‐Leu) (5), cyclo (L ‐Val‐L ‐Ala) (6), 5‐methyluracil (7) and uracil (8), was isolated from Nocardia alba sp.nov (YIM 30243^T), which was isolated from a soil sample collected from Yunnan Province, P. R. China. NMR techniques including COSY, HSQC, ROESY, and HMBC were used to elucidate the structures of these compounds. We report the unambiguous assignments of the ¹H and ¹³C NMR spectra of the new compound nocarsin A (1). Copyright © 2009 John Wiley & Sons, Ltd.     

Tasumatrols P – T,Five New Taxoids from Taxus sumatrana

The phytochemical investigation of the more polar fractions from the leaves and twigs of Taxus sumatrana (Taxaceae) afforded five new taxane diterpene esters, tasumatrols P–T ( 1 – 5 ) possessing an 11(15→1),11(10→9)‐diabeotaxane skeleton. Compounds 1, 4 , and 5 contain an α‐hydroxy group at C(14), while 3 has no OH group at either C(13) or C(14). Compound 2 is a natural 4,5‐acetonide derivative, while 4 has an unusual spiro‐connected 2‐hydroxy‐2‐phenyl‐1,3‐dioxolane ring. Ten known taxoids, were also isolated in the course of the chromatographic fractionation. Five additional new O‐acetyl derivatives 3a, 4a, 4b, 5a , and 5b were prepared from the taxanes 3 – 5 . The structures of all new compounds were established on the basis of their spectroscopic analyses. Compound 1 showed mild cytotoxic activity against human Hela and Daoy tumor cells.     

Glykoside von Marsdenia erecta R. Br. 2. Mitteilung: Versuche zur Strukturbestimmung der Genine. Glykoside und Aglykone, 330. Mitteilung

Structures for the genins of the ester glycosides of Marsdenia erecta are suggested. They are based on the behaviour in alkaline hydrolysis of these ester glycosides, their NMR. and mass spectra and ORD. data. All genins are derived from three acyl-free pregnane derivatives, i.e. drevogenin-P ( 1 ), 17 β-marsdenin ( 3 ) and marsectohexol ( 7 ). The structure of 1 is known, 3 and 7 are new compounds, i.e. 3 = 3β,8β,11α,12β,14β-pentahydroxy-Δ⁵-pregnen-20-one and 7 = 3β,8β,11α,12β,14β,20ξ-hexahydroxy-Δ⁵-pregnene. Formulae 13–17 were attributed to the acyl-genins A-1, A-2, A-3, A-4 and A-5, but only two of them were pure compounds, i.e. acyl-genin A-3 = 11,12-di-O-tiglyl-17β-marsdenin ( 15 ) and acyl-genin A-5 = 11,12-di-O-acetyl-marsectohexoi ( 17 ). Acyl-genin A-1 is a mixture of the two esters 13a + 13b derived from drevogenin-P, and similarly acyl-genin A-2 is a mixture of the esters 14a + 14b derived from 17β-marsdenin. The poorly characterised acyl-genin A-4 is most probably a mixture of the esters 16a + 16b , also derived from 17β-marsdenin.     

Notiz über das Vorkommen von 4′,5-Dihydroxy-3,3′,6,7-tetramethoxyflavon (Chrysosplenetin) in Plectranthus marrubioides HOCHST (Labiatae)

Chrysosplenetin (4′, 5-dihydroxy-3,3′, 6,7-tetramethoxyflavon) has been isolated from the leaves of Plectranthus marrubioides HOCHST (Labiatae).     

Reaktionen von 3-Dimethylamino-2,2-dimethyl-2H-azirin mit. NH-aciden Heterocyclen; Synthese von 4H-imidazolen

Reactions of 3-Dimethylamino-2,2-dimethyl-2H-azirine with NH-Acidic Heterocycles; Synthesis of 4H-Imidazoles In this paper, reactions of 3-dimethylamino-2,2-dimethyl-2H-azirine ( 1 ) with heterocyclic compounds containing the structure unit CO? NH? CO? NH are described. 5,5-Diethylbarbituric acid ( 5 ) reacts with 1 in refluxing 2-propanol to give the 4H-imidazole derivative 6 (Scheme 2) in 80% yield. The structure of 6 has been established by X-ray crystallography. Under similar conditions 1 and isopropyl uracil-6-carboxylate ( 7 ) yield the 4H-imidazole 8 (Scheme 3), the structure of which is deduced from spectral data and the degradation reactions shown in Scheme 3. Hydrolysis of 8 with 3N HCl at room temperature leads to the α-ketoester derivative 9 , which in refluxing methanol gives dimethyl oxalate and 5-dimethyl-amino-2,4,4-trimethyl-4H-imidazole ( 10 ). On hydrolysis the latter is converted to the known 2,4,4-trimethyl-2-imidazolin-5-one ( 11 ) [6]. Quinazolin-2,4 (1H, 3H)-dione ( 12 ) and imidazolidinetrione (parabanic acid, 14 ) undergo with 1 a similar reaction to give the 4H-imidazoles 13 and 15 , respectively (Schemes 4 and 5). In Scheme 6 two possible mechanisms for the formation of 4H-imidazoles from 1 and heterocycles of type 16 are formulated. The zwitterionic intermediate f corresponds to b in Scheme 1. Instead of dehydration as in the case of the reaction of 1 with phthalohydrazide [3], or ring expansion as with saccharin and cyclic imides [1] [2], f , undergoes ring opening (way A or B). Decarboxylation then leads to the 4H-imidazoles 17 .     

Edulon A,ein 2H-1-Oxapyrenderivat aus Plectranthus edulis (Labiatae)

Edulon A, a Derivative of 2H-1-Oxapyrene from Plectranthus edulis (Labiatae From the coloured leaf-glands of the above mentioned East-african labiate we have isolated Edulon A, A new, deeply coloured diterpenoid. Based mainly on spectroscopic arguments, we propose its structure to be (5a R, 1′ ζ)-10-(2′-acetoxy-1′-methylethyl)-6, 7, 9-trihydroxy-3, 5a-dimethyl-4, 5, 5a, 8-tetrahydro-2H,-l-oxapyrene-2, 8-dione (1a) . The compound may be regarded as a 4, 5-seco-abietane derivative that has formed new bonds (between C(18 or 19)? COOH and C(12)? OH), and between C(3) and C (11)) by lactonisation and condensation, respectively.     

Phenolic Compounds from Scorzonera tomentosa L.

From the subaerial parts of S. tomentosa L. (Asteraceae), two new dihydroisocoumarins, compounds 1 and 2 , a new phthalide, 3 , and a new stilbene derivative, 4 , were isolated, together with four known compounds, (±)‐hydrangenol ( 5 ), (?)‐hydrangenol 4′‐O‐β‐glucoside ( 6 ), (±)‐hydramacrophyllol A ( 7 ), and (±)‐hydramacrophyllol B ( 8 ). All secondary metabolites were identified on the basis of physicochemical, spectroscopic, and mass‐spectrometric data. The known compounds 5 – 8 were isolated for the first time from this species.     

Nachweis von C (15)-epimeren Coleonen C und D in der Natur und ihre Bedeutung für den sterischen Verlauf der Bildung des Spirocyclopropanrings

Natural Occurrence of C(15)-Epimeric Coleons C and D and its Significance to the Stereochemistry of the Formation of a Spirocyclopropanring In a previous paper some evidence was presented for a predominant occurrence of epimeric coleons ((15S)-coleon C ((15 S)- 1a ), and (15S)-coleon D ((15S)- 2a )) in Plectranthus lanuginosus [1], The proposed structures have now been proven by careful comparison of their physical data with those of the already described C(15)-epimers whose structures were deduced by X-ray analysis of a derived cis-diketone 3 [5], Examination of the epimeric purity of coleons possessing a 2-hydroxy-1-methylethyl side-chain (coleons C , D , H , I , I ′ and derivatives) isolated from seven different species (Coleus, Plectranthus and Solenostemon) has shown that these coleons always occur as a mixture of C(15)-epimers, although in most cases with one predominant epimer. The consequences for the stereochemistry of the postulated in vivo formation of the methyl-substituted spirocyclopropane substructure is discussed.     

Rotundifolides A and B,Two New Enol‐Derived Butenolactones from the Bark of Litsea rotundifolia var. oblongifolia

Two new enol‐derived butenolactones, rotundifolides A ( 1 ) and B ( 2 ), along with four known related compounds, lincomolide C ( 3 ), lincomolide A ( 4 ), marliolide ( 5 ), and litsenolide A₁ ( 6 ), were isolated from the bark of Litsea rotundifolia var. oblongifolia. The structures of the new metabolites were characterized by spectroscopic methods and comparison with known compounds.