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.     

Partialsynthesen und Reaktionen von Abietanderivaten (Lanugonen) aus Plectranthus lanuginosus und verwandten Verbindungen

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. 19 → 26 and 27 ; 28 → 29 . The possible natural occurrence of these compounds is emphasized.     

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.     

Diterpenoide Drüsenfarbstoffe aus Labiaten: 22 neue Coleone und Royleanone aus Plectranthus lanuginosus

Leaf-gland Pigments from Labiatae: 22 Novel Diterpenoids (Coleons and Royleanones) from Plectranthus lanuginosus We report the isolation and structure elucidation of 22 novel diterpenoids (named lanugones A, B, C, D, E, F, G, H, I, J, K, K′, L, M, N, O, P, Q, R, S and (155)-coleon C ( 28 ) and (155)-coleon D ( 29 )) from the leaf-glands of the above-mentioned plant (see Table 1). Structurally they belong to the subgroups of royleanones and coleons with the following structural characteristics: 8-hydroxy-1-methyl-spi-ro[2,5]oct-5-ene-4,7-diones, p-quinomethanes, extended (vinylogous) quinones, di-osphenols and diketones. Compounds 28 and 29 are (15S)-epimers of the already known coleon C and coleon D (with (15 R)-configuration), respectively. Furthermore, the already known 6,7-didehydroroyleanone ( 1 ) has been isolated in small amount. The present investigation has uncovered the broadest range of diverse chromo-phoric systems and oxydation levels so far found amongst diterpenoids in a single plant species. Most important for an understanding of the metabolic fate of an iso-propyl group is the full range found with the following metabolic stages: isopropyl-→ hydroxyisopropyl → dihydrofuran and spirocyclopropane → allyl- and 2-hydroxypropyl groups.     

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.     

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.     

Stereoselective in-vitro aromatic-ring oxygenations of chiral 1,4-benzodiazepin-2-ones

Biological N(1)-demethylation and C(3)-hydroxylation of two enantiomeric 1,4-benzodiazepin-2-ones 1 and 2 (cf. scheme 2) were found to be nonstereoselective. Aromatic-ring hydroxylation, however, took place in the (S)-series only, leading to 3′- and 4′-hydroxylated, N(1)-demethylated, metabolites ( 54 and 56 , cf. scheme 5: these structures were unambiguously confirmed by comparing their UV., CD., and mass spectra with those of authentic specimens). Several compounds, theoretically conceivable as products of hydroxylation in the aromatic A-ring of 1 and 2 by mechanisms including the NIH-shift (cf. scheme 3), were synthesized but none of these compounds was yet isolated from in vitro incubation mixtures.     

Isolierung und Strukturaufklärung von 36 Diterpenoiden aus Trichomen von Plectranthus edulis (VATKE) T.T. AYE

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(4→3) 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.     

Drüsenfarbstoffe aus Labiaten: Ecklonochinone A und B,zwei neuartige Dibenzo-p-dioxin-o-chinone aus Plectranthus ecklonii BENTH

Leaf-gland Pigments from Labiatae: Ecklonoquinones A and B, Two Novel Dibenzo-p-dioxine-o-quinones from Plectranthus ecklonii BENTH From the leaf-glands of the above mentioned labiate the following compounds have been isolated and their structures established: ecklonoquinone A ( 1 ) and ecklonoquinone B ( 2 ), two novel isomeric dibenzo-p-dioxine-orthoquinones; 2 (S)-5,4′-dihydroxy-6,7-dimethoxyflavanone ( 8 ); the already known flavone cirsimaritin ( 9 ) and the diterpenoid p-quinomethane parvifloron F ( 10a ). The spectral data of the dimeric p-menthanes 1 and 2 are very similar, and only analysis of the ¹H-coupled ¹³C-NMR.-spectra lead to structures 1 and 2 , respectively. Our tentative assignment of these structures to the individual molecules is based on a comparison of the spectral data with the synthetic compound 7 .     

Der Sterische Verlauf der nucleophilen Cyclopropanöffnung an den vier im Spiro(methylcyclopropan)-Ring Diastereoisomeren Lanugonen J (Spirocoleonen)

The Stereochemistry of the Nucleophilie Opening of the Cyclopropane Ring in the four Diastereoisomeric Lanugons J (Spirocoleons) Methanolysis of the spiro(methylcyclopropane) moiety in the four diastereoisomeric lanugons J 3 (13S, 15R), 4 (13R,15R), 5 (13S,15S), and 6 (13R,15S) is shown to proceed stereospecifically with inversion of the configuration at the attacked C-atom (C(15)). The resulting epimeric 2-methoxypropyl-substituted hydroxy-1,4-benzoquinones (royleanones) 7a/8a (monomethoxy derivatives) and 7b/8b (dimethoxy derivatives) could be separated by HPLC using the recently described ‘Non-Aqueous Cation Exchange System’. Respective pairs of ¹H-NMR spectra exhibit minute but significant differences in the ABMX₃ part of the 2-methoxypropyl group. The final structure assignment is based on a single-crystal X-ray analysis of the dimethoxyroyleanone 7b , whose absolute configuration was established by chiroptical correlation with known abietanoids. Thus, methanolysis of 3 and 4 ((R)-configuration at the reaction centre) yielded the royleanones 7a and 7b with (S)-configuration, whereas analogous treatment of 5 and 6 ((S)-configuration at the reaction centre) led to the corresponding derivatives 8a and 8b both having the (R)-configuration in the 2-methoxypropyl side chain.     

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 .     

Reaktionen von N-alkoxycyclimoniumsalzen—V: Vinyloge phosphorane aus N-methoxypyridiniumsalzen

In dipolar aprotic solvents (DMF, HMPT a.o.) cyano substituted N-methoxypyridinium salts 1 undergo ring cleavage by ethoxycarbonylmethylene(triphenyl)phosphorane to form vinylogous phosphoranes 6. All-trans-configuration of the conjugated double bonds is derived from NMR spectra of the ring opened compounds.     

Horminon,Taxochinon und weitere Royleanone aus 2 abessinischen Plectranthus-Spezies (Labiatae)

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.     

Paecilomycines A and B,Novel Diterpenoids,Isolated from Insect‐Pathogenic Fungi Paecilomyces sp. ACCC 37762

Two new diterpenoids, named paecilomycine A ( 1 ) and paecilomycine B ( 2 ), including a novel skeleton with a five‐membered lactone ring, together with three known labdane diterpenoids, rel‐(1R,3S,4aS,5R,8aS)‐5‐[(3E)‐4‐carboxy‐3‐methylbut‐3‐en‐1‐yl]decahydro‐3‐hydroxy‐1,4a‐dimethyl‐6‐methylidenenaphthalene‐1‐carboxylic acid ( 3 ), botryosphaerin E ( 4 ), and agathic acid ( 5 ), were isolated from solid culture of the insect pathogenic fungi strain Paecilomyces sp. The structures of all compounds were established on the basis of comprehensive spectroscopic studies. The relative configurations of 1 and 2 were determined by single‐crystal X‐ray diffraction analyses.     

Die Ableitung der Stereochemie von 1-Isopropyl-4-methyl-bicyclo[3.1.0]hexan (cis-und trans-Thujan) durch Protonenresonanz-Spektroskopie

100 Mc/s proton NMR. spectra of the two diastereoisomeric thujanes obtained by reduction natural thujone have been measured and are given a detailed analysis. The relative configurations of the two hydrocarbons are deduced. Together with the known R-configuration at C(1) the absolute configurations can be derived, (?)-cis-thujane having the (1R:4S:5R)- and (+)-trans-thujane the (1R:4R:5R)-configuration. It can be shown that the trans-isomer adopts a boat-like conformation of the bicyclohexane ring system whereas cis-thujane prefers a half-chair conformation with a flattened cyclopentane ring.     

Zur Konfiguration des Vitamin-D3-Metaboliten 25, 26-Dihydroxycholecalciferol: Synthese von (25S,26)- und (25R,26)-Dihydroxycholecalciferol

Configuration of the Vitamin-D₃-Metabolite 25,26-Dihydroxycholecalciferol: Synthesis of (25S,26)- and (25R,26)-Dihydroxycholecalciferol For selective synthesis of the title compounds, (25S)- 1b and (25R)- 1b (Scheme 1), the protected cholesterol precursors (25S)- 6 and (25R)- 6 were prepared from stigmasterol-derived steroid-units 4a-d and C₅-side chain building blocks 5a–d by Grignard- or Wittig-coupling (Scheme 2), the configuration at C(25) of the target compounds being already present in the C₅-units. Conversion of the cholesterol intermediates to the corresponding vitamin-D₃ derivatives was carried out via the 7,8-didehydrocholesterol compounds (25S)- 2b and (25R)- 2b (Scheme 1), using the established photochemical-thermal transformation of the 5,7-diene system to the seco-triene system of cholecalciferol. The configuration at C(25) of the cholesterol precursors as assigned on basis of the known configuration of the C₅-units used, was found to be in agreement with the result of a single crystal X-ray analysis on compound 11 . The configuration at C(25) remained untouched on conversion of the cholesterol ring system to the seco-triene system of vitamin D₃ as evident from comparison of the lanthanide-induced CD. Cotton effects observed for (25S)- 3b and (25S) 1b . 25,26-Dihydroxycholecalciferol observed as a natural vitamin-D₃ metabolite has (25S)-configuration.     

Fredericone,neue hochfunktionalisierte Abietanoide aus Blattdrüsen von Coleus fredericii G. TAYL

Fredericon A, B, C, and D, Novel and Highly Functionalized Abietanoids from Leaf-Glands of Coleus fredericii From the leaf-glands of the title plant (fam. Labiatae) two novel, genuie spirocycloopropyl-coleons have been isolated and structurally characterized. Fredericon A (1) bears the unusal 1,1,2-tricarbonylcyclopropane substructure that renders the molecule very suseptible to nucleophile-promoted rearrangements. Biogenetically intriguing is the presence of a 3-acetoxypropyl side-chain in fredericon B ( 3 ). Its formation from the well known isopropyl group is explained by transformation of the latter into a spirocyclopropane, followed by a reductive opening of the cyclopropane and reducation of the aldehyde, MeOH addition to 1 , yields fredericon C ( 5 ), a derivative of 1H-phenanthro[3,2-b]pyran-7,12(2H,8H)-dione by two consecutive introlecular nucleophilic openings of the cyclopropane ring and the derived methoxy-oxirane. Similar methanolysis of a crude fraction of 1 , produced, in addition to 5 , the fredericon D, a novel derivative of 3H-phenanthro[3,2-b]pyran-2-(4H)-one( 6 ).     

Synthesis and Characterization of Nitrogen and Sulfur Containing 1,4-Naphthoquinones

Abstract

New N,S-disubstituted naphthoquinones were synthesized by reactions of S- and N-nucleophiles with 2,3-dichloro-1,4-naphthoquinone. 2-(Hexadecylthio)-3-(phenylamino)-naphthalene-1,4-dione 5a was synthesized by reaction of 2-chloro-3-(phenylamino)-naphthalene-1,4-dione 3a with hexadecanethiol 4a. The structures of the new synthesized naphthoquinone derivatives were determined by micro analyses and spectroscopic methods (FT-IR, ¹H NMR, ¹³C NMR, MS, and UV/Vis.). Photo- and electrochemical properties of selected compounds were investigated by using fluorescence spectroscopy and the cyclovoltammetry method.     

Drüsefarbstoffe aus Labiaten: Identifizierung von 17 Abietanoiden aus Plectranthus sanguineus BRITTEN

Pigments from Leaf-Glands from Labiatae: 17 Quinonoid Abietanoids from Plectranthus sanguineus BRITTEN From the glandular trichomes of the title plant from Nyasaland, Malawi, 17 abietanoid quinones and hydroquinones were isolated and identified, the most interesting amongst them being the novel tricyclic, sevenmembered anhydride 8 . A detailed HPLC separation of the compounds is presented.     

Diterpenoide Drüsenfarbstoffe aus Labiaten: 6 neue p-Chinomethane aus Plectranthus parviflorus WILLD

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 .