Identification of farnesol as an intermediate in the biosynthesis of cantharidin from mevalonolactone

Identification of farnesol as an intermediate in the biosynthesis of cantharidin from mevalonolactone Simultaneous injection of 2-[¹⁴C]-mevalonolactone (2-[¹⁴C]- 1 ) and (E,E)-11′,12-[³H]-farnesol (11′,12-[³H]- 2 ) into Lytta vesicatoria L . (Coleoptera, Meloidae) yields doubly labelled cantharidin ( 3 ). The remainder of the precursor farnesol, re-isolated from the insects after the incubation period, has incorporated ¹⁴C-radioactivity. The labelling pattern in this farnesol, as determined by two independent degradative reaction sequences, is in agreement with the isoprene rule. Since specific incorporation of farnesol ( 2 ) into cantharidin ( 3 ), and of mevalonolactone ( 1 ) into both, farnesol ( 2 ) and cantharidin ( 3 ) is observed, the sesquiterpene alcohol 2 acts as an intermediate in the biosynthesis of the C₁₀-compound 3 (Scheme 1).     

On the incorporation of geraniol and farnesol into cantharidin (author's transl)

On the incorporation of geraniol and farnesol into cantharidin Earlier investigations [1] have shown that cantharidin (1) is biosynthesized by the male Lytta vesicatoria L. (Meloidae, Coleoptera) from the common terpenoid precursors mevalonate and farnesol (3) . To prove if geraniol (2) is incorporated via farnesol (3) into cantharidin (1) the following geraniols have been synthesized and injected into either larvae or male adult Lytta vesicatoria, partly in a mixture with synthetic 11′, 12-[³H]-farnesol as an internal standard: 2-[¹⁴C]-, 7-[¹⁴C]-, 7′, 8-[¹⁴C]-, 7′, 8-[³H]-geraniol. Unexpectedly, geraniol (2) was not specifically incorporated into cantharidin (1) perhaps due to its higher toxicity or its faster degradation relative to the other precursors before incorporation. The incorporation of U-[¹⁴C]-leucine, U-[¹⁴C]-isoleucine and 1-[¹⁴C]-glucose into cantharidin (1) via their metabolites is evident by degradation studies, whereas 1-[¹⁴C]- and 2-[¹⁴C]-glycine do not serve as precursors for cantharidin (1) .     

Experimente zum kompetitiven Einbau der Stereoisomeren des Farnesols in Cantharidin. 6. Mitteilung zur Biosynthese des Cantharidins

Experiments on the competitive incorporation of farnesol-stereoisomers into cantharidin Farnesol ( 2 ) has been demonstrated to be an efficient precursor for cantharidin ( 1 ), into which it is transformed by elimination of C(1), C(5), C(6), C(7) and C(7′) [1]. The following incorporation experiments with doubly labelled (³H and ¹⁴C) stereoisomers of farnesol present strong evidence that (E,E)- farnesol ((E,E)- 2 ) in fact is the precursor for cantharidin, whereas (2E, 6Z)- 2 and (Z,Z)- 2 are not utilized for the biosynthesis of cantharidin. A possible mechanism for the incorporation of (2Z,6E)-farnesol ((2Z,6E)- 2 ) to an extent of 56,8% relative to (E,E)- 2 is discussed.     

Succinct and Facile Synthesis of Innovative Thiopyrimidines With Antimicrobial and Antitubercular Investigation

Abstract

To develop a series of bioactive heterocycles in minimum number of steps, 3-methyl- 4-(substituted phenyl)-1-phenyl-4,8-dihydropyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidine-5,7 (1H,6H)-dithione 2(a–j), 4-(4-substituted phenyl)-5-imino-3-methyl-1,6-diphenyl-4,5,6,8-tetrahydropyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidine-7(1H)-thione 3(a–j), and N-[4-(subs- tituted phenyl)-3-methyl-1-phenyl-7-thioxo-1,4,7,8-hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidine-5-yl]thiourea 4(a–j) have been synthesized from amino nitrile functionality 1(a–j). The structures of the compounds were elucidated by IR, ¹H NMR, elemental analysis, and some representative ¹³C NMR and mass spectra. All the title compounds were screened for antimicrobial and antitubercular activities, while some representative compounds were tested for antioxidant activity. Out of synthesized compounds, compounds 1j (4-CH₃), 2d (4-F), 4c (4-OH), and 4i (3-Br) exhibited maximum inhibition against Mycobacterium Tuberculosis H₃₇Rv. Compound 3c (4-OH) revealed elevated efficacy against all tested bacterial strain, while compounds 1i (3-Br), 2c (4-OH), and 3h (3-NO₂) were found efficacious against Candida albicans as compared to standard drugs.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis and Reactions of Pyrido[2,1‐a]isoquinolin‐4‐yl Formimidate Derivatives and Antimicrobial Activities of Isolated Products

Treatment of arylidene malononitriles 2A – C with 1‐cyanomethylisoquinoline 1 afforded 4‐amino‐2‐arylpyrido[2,1‐a ]isoquinoline‐1,3‐dicarbonitrile derivatives 5A – C , which converted to formimidates 6A – C via reaction with triethylorthoformate. Treatment of the latter compounds with hydrazine hydrate gave the corresponding amino–imino compounds 7A – C , which underwent Dimroth rearrangement to afford 13‐aryl‐1‐hydrazinylpyrimido[5′,4′:5,6]pyrido[2,1‐a ]isoquinoline‐12‐carbonitrile 8A – C . The latter reacted with aldehyde to give 9a – i . Oxidative cyclization of the latter compounds 9a – i gave [1,2,4]triazolo[4″,3″:1′,6′]‐pyrimido[5′,4′:5,6]pyrido[2,1‐a ]isoquinolines 10a , d , g . Such compounds isomerized to the thermodynamically more stable isomers [1,2,4]triazolo[1″,5″:1′,6′]pyrimido[5′,4′:5,6]‐pyrido[2,1‐a ]isoquinolines 11a , d , g . Antimicrobial activities for some compounds were studied.     

Synthesis,Physical Properties and Memory Device Application of a Twelve‐Ring Fused Twistheteroacene

Developing new organic conjugated materials for high density memory devices is highly desirable. In this research, a novel donor–acceptor‐type twelve‐ring fused twistheteroacene, 2,7,19,24‐tetra‐tert ‐butyl‐13,30‐didodecyl‐9,17,26,34‐tetraphenyl benzo[8′,9′]triphenyleno[2′,3′:7,8]dibenzo[b,e][1,4]dioxino[1,2,3,4‐lmn]dibenzo[6′,7′:10′,11′]tetraceno[2′,3′:5,6][1,4]dioxino[2,3‐f][3,8]phenanthroline‐12,14,29,31(13H ,30H )‐tetraone ( DPyN ) has been synthesized and characterized. It displays high thermal stability, possesses a broad absorption band centered at 510 and 538 nm, and emits red fluorescence in organic solvents. A solution‐processed memory device with DPyN as an active element shows an excellent memory performance with an ON/OFF current ratio of 10^3.46:1 and a threshold voltage of −2.44 V.     

Structure elucidation of [1,3]oxazolo[4,5‐e][2,1]benzisoxazole and naphtho[1,2‐d][1,3]‐ and phenanthro[9,10‐d]oxazoles using gradient selected gHMBC,gHMQC and gHMQC‐TOCSY NMR techniques

Structure elucidation of compounds in the benzisoxazole series ( 1 – 6 ) and naphtho[1,2‐d][1,3]‐ ( 7 – 10 ) and phenanthro[9,10‐d][1,3]oxazole ( 11 – 14 ) series was accomplished using extensive 2D NMR spectroscopic studies including ¹H–¹H COSY, long‐ range ¹H–¹H COSY, ¹H–¹³C COSY, gHMQC, gHMBC and gHMQC‐TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one‐bond ¹J_{C2, H2} (or ¹J_{C3, H3}) coupling constants. Complete analysis of the ¹H NMR spectra of 11 – 14 was achieved by iterative calculations. Gradient selected gHMQC‐TOCSY spectra of phenanthro[9,10‐d][1,3]oxazoles 11 – 14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H‐5, H‐6 and at H‐9 and H‐7 and H‐8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd.     

Five-membered 2,3-dioxo heterocycles: XCII. Reaction of 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with ethyl (2Z)-(3,3-dimethyl-8-oxo-2-azaspiro[4.5]deca-6,9-dien-1-ylidene)ethanoate. Synthesis of bridged analogs of pyrrolizidine alkaloids

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones reacted with ethyl (2Z)-(3,3-dimethyl-8-oxo-2-azaspiro[4.5]deca-6,9-dien-1-ylidene)acetate to give ethyl 6′-aryl-2′-(2-hydroxyphenyl)-11′,11′-dimethyl-3′,4,4′,13′-tetraoxospiro[2,5-cyclohexadiene-1,9′-(7′-oxa-2′,12′-diazatetracyclo[6.5.1.0^1,5.0^8,12]tetradec-5′-ene)]-14′-carboxylates whose structure was confirmed by X-ray analysis. The products may be regarded as bridged analogs of pyrrolizidine alkaloids, 7′-oxa-2′,12′-diazatetracyclo[6.5.1.01,5.08,12]tetradecanes.     

Photochemische Reaktionen. 118. Mitteilung [1] Zur vinylogen β-Spaltung von Enonen. UV.-Bestrahlung von 4-(3',7',7'-Trimethyl-2'-oxabicyclo [3.2.0]hept-3'-en-1'-yl)but-3-en-2-on

Vinylogous β-Cleavage of Enones: UV.-irradiation of 4-(3′,7′,7′-trimethyl-2′-oxabicyclo[3.2.0]hept-3′-ene-1′-yl)but-3-ene-2-on On ¹π,π*-excitation (λ = 254 nm) in acetonitrile (E/Z)- 2 is converted into the isomers 4–9 and undergoes fragmentation yielding 10 ; in methanol (E/Z)- 2 gives 7–10 and is transformed into 11 by incorporation of the solvent. On ¹π,π*-excitation (λ λ?347 nm; benzene-d₆) (E)- 2 is isomerized into (Z)- 2 , which is converted into the isomers 3 and 4 by further irradiation. ¹π,π*-Excitation (λ = 254 nm; acetonitrile) of 4 gives 6 and (E)- 9 , whereas UV.-irradiation (λ = 254 nm; acetonitrile-d₃) of 5 yields (E)- 7 and 8 . On ¹π,π*-excitation (λ = 254 nm; acetonitrile) of (E/Z)- 12 the compounds (E)- 14 and (E)- 15 are obtained.     

Ironcarbonyl Complexes of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene Derivatives. Synthesis of Substituted Tricarbonyl(ortho-quinodimethane)iron Complexes and 2-Indanones

The l-dimethoxymethyl-5,6-dimethyldene-7-oxabicyclo[2.2.1]hept-2-ene ( 9 ) has been prepared. On treatment with Fe₂(CO)₉, the endocyclic double bond C(2)?C(3) was coordinated first giving the corresponding exo-Fe(CO)₄ complex 10 . The latter reacted with Fe₂(CO)₉ and afforded cis-heptacarbonyl-μ-[1RS,2SR,3RS,4SR,5RS,6SR-2,3-η: C5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]diiron ( 11 ) as a major product. On heating, 11 underwent deoxygenation of the 7-oxabicyclo[2.2.1]heptene moiety yielding tricarbonyl[C,5,6,C-η-(1-(dimethoxymethyl)-5,6-dimethylidenecyclohexa-1,3-diene)]iron ( 13 ). In MeOH, a concurrent, regioselective methoxycarbonylation was observed giving tricarbonyl[C,3,4,C-η-(methyl 5-(dimethoxymethyl)-3,4-dimethylidenecyclohexa-1,5-diene-1-carboxylate)]iron ( 14 ). Oxidative removal of the Fe(CO)₃ moiety in 13 and 14 did not afford the expected ortho-quinodimethane derivatives but led to CO insertions giving 2,3-dihydro-2-oxo-1Hindene-4-carbaldehyde ( 20 ) and methyl 7-formyl-2-3-dihydro-2-oxo-lH-indene-5-carboxylate ( 21 ), respectively.     

Pteridine. Teil XCIV. Synthese und Eigenschaften von 5,6-Dihydro-6-(1,2,3-trihydroxypropyl)pteridinen: Kovalente intramolekulare Addukte

Pteridines: Synthesis and Characteristics of 5,6-Dihydro-6-(1,2,3-trihydroxypropyl)pteridines: Covalent Intramolecular Adducts Various 5,6-diaminopyrimidines ( 1, 15, 24, 33 ) were condensed with the phenylhydrazones of L -( 2 ) and D -arabinose ( 3 ) in acidic medium under N₂ to give formal 5,6-dihydro-6-(1,2,3-trihydroxypropyl)pteridines (see, e.g., 4 and 5 ), the latter turned out to exist preferentially as intramolecular adducts, the hexahydropyrano-[3,2-g]pteridines 6, 7, 16, 17, 25, 26 , and 34 , formed subsequently by addition of the terminal OH group of the side-chain to the C(7)?N(8) bond of the pteridine moiety. Spectroscopically, the isomeric hexahydrofuro-[3,2-g]pteridines 10,11,18,19 , and 35 were also detected as minor components in the equilibrium mixtures. In the 4-amino-2-(methylthio)pteridine series, crystallization of 6 and 7 led to the stereochemically pure (3S,4R,4aR, 10aS)-6-amino-3,4,4a,5,10,10a-hexahydro-8-(methylthio)-2H-pyrano[3,2-g]pteridine-3,4-diol ( 8 ) and its corresponding enantiomer 9 , respectively Structure 8 was proven by X-ray analysis. Acylation of the hexahydropyrano[3,2-g]pteridines yielded the more stable tri-, tetra-, and pentaacetyl derivatives 12–14, 20–23, 27–32 , and 37–39 which were characterized and of which the absolute and relative configurations were determined (¹H- and ¹³C–NMR and UV spectra, chiroptical measurements, elemental analyses).     

Chemo- and Stereoselective Coordination of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene by d8- and d6-Metal Carbonyls. Diels-Alder reactivity of Dienes Perturbed by Remote Olefin Complexation

The endocyclic double bond C(2), C(3) in 5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene ( 1 ) can he coordinated selectively on its exo-face before complexation of the exocyclic s-cis-butadiene moiety. Irradiation of Ru₃(CO)₁₂ or Os₃(CO)₁₂ in the presence of 1 gave tetracarbonyl [(1R,2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene)]ruthenium ( 6 ) or -osmium ( 8 ). Similarly, irradiation of Cr(CO)₆ or W(CO)₆ in the presence of 1 gave pentacarbonyl[(1R, 2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]chromium (10) or -tungsten (11) . Irradiation of complexes 6 and 11 in the presence of 1 led to further CO substitution giving bed-tricarbonyl-ae-bis[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]ruthenium ( 7 ) and trans-tetracarbonyl[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo-[2.2.1]hept-2-ene)]tungsten (12) , respectively. The diosmacyclobutane derivative cis-m?-[(1R,3R,3S,4S)-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hepta-2,3-diyl)]bis(tetracarbonyl-osmium) (Os-Os) (9) wa also obtained. The Diels-Alder reactivity of the exocyclic s-cis-butadiene moiety in complexs 7 and 8 was found to be significantly higher than that of the free triene 1 .     

Acid-Catalyzed Rearrangements of 5,6-exo-Epoxy-7-oxabicyclo[2.2.1]hept-2-yl Derivatives. Migratory Aptitudes of Acyl vs. Alkyl Groups in Wagner-Meerwein Transpositions

In the presence of HSO₃F/Ac₂O in CH₂CL₂, 2-exo- and 2-endo-cyano-5,6-exo-epoxy-7-oxabicyclo[2.2.1]hept-2-yl acetates ( 6a , b ) gave products derived from the epoxide-ring opening and a 1,2-shift of the unsubstituted alkyl group (σ bond C(3)–C(4)). In contrast, under similar conditions, the 5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptan-2-one ( 6c ) gave 5-oxo-2-oxabicyclo[2.2.1]heptane-3,7-diyl diacetates 20 and 21 arising from the 1,2-shift of the acyl group. Acid treatment of 5,6-exo-epoxy-2,2-dimethoxy-7-oxabicyclo[2.2.1]heptane ( 6d ) and of 5,6-exo-epoxy-2,2-bis(benzyloxy)-7-oxabicyclo[2.2.1]heptane ( 6e ) gave minor products arising from epoxide-ring opening and the 1,2-shift of σ bond C(3)–C(4) and major products ( 25 , 29 ) arising from the 1,3-shift of a methoxy and benzyloxy group, respectively. Under similar conditions, 5,6-exo-epoxy-2,2-ethylenedioxy-7-oxabicyclo[2.2.1]heptane ( 6f ) gave 1,1-(ethylenedioxy)-2-(2-furyl)ethyl acetate ( 32 , major) and a minor product 33 , arising from the 1,2-shift of σ bond C(3)–C(4). The following order of migratory aptitudes for 1,2-shifts toward electron-deficient centers has been established: acyl > alkyl > alkyl α-substituted with inductive electron-withdrawing groups. This order is valid for competitive Wagner-Meerwein rearrangements involving equilibria between carbocation intermediates with similar exothermicities.     

Synthesis of substituted dihydrobenzo[f]pyrimido[4,5-b]-quinolines as tetracyclic 5-deaza nonclassical folates

Cyclocondensation of 2,4,6-triaminopyrimidine ( 10 ) with chlorovinyl aldehyde 7 afforded the linear regioisomer 9,1 1-diamino-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 1 ) while the cyclocondensation of 2,6-diamino-4-hydroxypyrimidine ( 11 ) or 6-amino-2,4-dihydroxypyrimidine ( 12 ) with chlorovinyl aldehyde 7 was regiospecific affording the linear regioisomers 9-amino-11-oxo-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 2 ) and 9,11-dioxo-5,6-dihydrobenzo[f]pyrimido[4,5-c]quinoline ( 3 ) respectively. The linear structures of these compounds were established by ¹H nmr and ¹³C nmr spectral data.     

Investigation of the reactions of fluorine containing 3-hydrazino-5H-1, 2, 4-triazino[5, 6-b]indoles with ethyl acetoacetate. Synthesis of some novel tetracyclic ring systems

Novel tetracyclic ring systems viz. 3-methyl-1-oxo-12H-1, 2, 4-triazepino[3′,4′:3, 4][1, 2, 4]triazino[5, 6-b]indole ( 4a ) and 3-methyl-5-oxo-12H-1, 2, 4-triazepino[4′,3′:2, 3][1, 2, 4]triazino[5, 6-b]indole ( 5a ), having angular and linear structures respectively, were synthesized by the cyclization of 3-oxobutanoic acid [5H-1, 2, 4-triazino-[5, 6-b]indole-3-yl]hydrazone ( 3a ). However, cyclization of 3b (R = CH_a, R¹ = R² = H) afforded the angular product 4b exclusively. Moreover, cyclization of 3c (R = R³ = H, R¹ = F) yielded 7-fluoro-1-0xo-10H-1, 3-imidazo[2′,3′:3, 4][1, 2, 4]triazino[5, 6-b]indole ( 6c ) and 7-fluoro-3-oxo-10H-1, 3-imidazo[3′,2′:2, 3][1, 2, 4]triazino-[5, 6-b]indole ( 7c ) instead of the expected triazepinone derivatives. Compound 3d (R = R¹ = H, R² = CF₃) also gave an imidazole derivative but only one angular product was obtained. In all these reactions, formation of the angular product involving cyclization at N-4 is favoured. Characterization of these products have been done by elemental analyses, ir, pmr, ¹⁹F nmr and mass spectral studies.     

Fused 1,2,4-triazole heterocycles. IV. Synthesis of four new heterocyclic ring systems of [1,2,4]triazolo[1,3]thiazinoquinolines

Syntheses of 5H-[1,2,4]triazolo[5′,1′:2,3][1,3]thiazino[5,4-c]quinolines 8, 5H-[1,2,4]triazolo[3′,4′:2)3][1,3]thiazino[5,4-c]quinolines 9, 5H-[1,2,4]triazolo[5′,1′:2,3][1,3]thiazino[5,6-c]quinolines 14 and 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,6-c]quinolines 15 are described starting from 4-chloro-3-chloromethylquinaldine (4) and 1,2,4-triazole-5-thiols 5 taking advantage of different reactivity of the chlorine atoms of 4 under different reaction conditions. The structures of products 8, 9, 14 and 15 and the intermediates leading to them were confirmed by desulfurization, unequivocal syntheses and nmr spectroscopy as well.     

Photochemische reaktionen von übergansmetall-olefinkomplexen: III. [4 + 6]-cycloaddition konjugierter diene an hexacarbonyl-μ-η6:6(-1,1′-bi(2,4,6-cycloheptatrien-1-yl)dichrom(O)

UV irradiation of hexacarbonyl-μ-η^6:6-1,1′-bi(2,4,6-cycloheptatrien-1-yl)dichromium(O) (I) in THF in the presence of 1,3-butadiene (A), E-1,3-pentadiene (B) and EE-2,4-hexadiene (C) causes preferentially a twofold [4 + 6]-cycloaddition and formation of the hexacarbonyl-μ-2–5 : 8.9-η-2′–5′ : 8′,9′-η-11,11′-bi(bicyclo-[4.4.1]undeca-2,4,8-trien-11-yl)dichromium(O) complexes (IVA–IVC). Partial decomplexation after the first [4 + 6]-cycloaddition yields isomeric tricarbonyl-2–5:8,9-η- (IIA–IIC) and tricarbonyl-2′–7′-η-{11-(2′,4′,6′-cycloheptatrien-1′-yl)bicyclo[4.4.1]undeca-2,4,8-triene}chromium(O) complexes (IIIA–IIIC). With 2,3-dimethyl-1,3-butadiene (D) mainly dicarbonyl-2–6 : 2′–4′-η-{1-(2′,3′-dimethyl-3′-buten-1′,2′-diyl)-7-(8″,9″-dimethylbicyclo[4.4.1]undeca-2″, 4″,8″-trien-11″-yl)cyclohepta-3,5-dien-2-yl}chromium(O) (VD) besides small amounts of pentacarbonyl-μ-2–6 : 2′–4′-η-2″–7″-η-{1-(2′,3′-dimethyl-3′-buten-1′,2′-diyl)-7-(2″, 4″,6″-cycloheptatrien-1″-yl)cyclohepta-3,5-dien-2-yl}dichromium(O) (VID) and tricarbonyl-2′-7′-η-{11-(2′,4′,6′-cycloheptatrien-1′-yl)-8,9-dimethyl-bicyclo[4.4.1]undeca-2,4,8-triene}-chromium(O) (IIID) is obtained. VD adds readily CO to yield tricarbonyl-2–5 : 8,9-η-11,11′-bi(8,9-dimethyl-bicyclo[4.4.1]undeca-2,4,8-trien-11-yl)chromium(O) (VIID). Finally D adds to VID under formation of pentacarbonyl-μ-2–6 : 2′–4′-η-2″–5″ : 8″,9″-η-{1-(2′,3′-dimethyl-3′-buten-1′,2′-diyl)-7-(8″,9″-dimethyl-bicyclo[4.4.1]- undeca-2″,4″,8″-trien-11″-yl)cyclohepta-3,5-dien-2-yl}dichromium(O) (VIIID). From IVA–IVC the hydrocarbon ligands (IXA–IXC) can be liberated by P(OCH₃)₃ in good yields. The structures of the compounds IIA–IXC were determined by IR     

Synthese von diastereo- und enantio-selektiv deuterierten β,ε-, β,β-, β,γ- und γ,γ-Carotinen

Synthesis of Diastereo- and Enantioselectively Deuterated β,ε-, β,β-, β,γ- and γ,γ-Carotenes We describe the synthesis of (1′R, 6′S)-[16′, 16′, 16′-²H₃]-β, εcarotene, (1R, 1′R)-[16, 16, 16, 16′, 16′, 16′-²H₆]-β, β-carotene, (1′R, 6′S)-[16′, 16′, 16′-²H₃]-γ, γ-carotene and (1R, 1′R, 6S, 6′S)-[16, 16, 16, 16′, 16′, 16′-²H₆]-γ, γ-carotene by a multistep degradation of (4R, 5S, 10S)-[18, 18, 18-²H₃]-didehydroabietane to optically active deuterated β-, ε- and γ-C₁₁-endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C₁₁ → C₁₄; C₁₄+C₁₂+C₁₄→C₄₀. NMR.- and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all-(E)-[²H₆]-β,β-carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.-effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′-²H₆]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.- and CD.-spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented.     

Conformational Analysis of Endoperoxides Grafted onto Bicyclo[2.2.n]alkanes as a Test of the Rigidity of the Bicyclic Skeleton. Photo-oxidation of [2.2.2] Hericene and 2,3,5,6-Tetramethylidenebicyclo[2.2.n]alkanes

The photo-oxidation of [2.2.2]hericene ( 6 ) gave successively the endoperoxides 11 (9,10,11,12-tetramethylidene-4,5-dioxatricyclo[6.2.2.0^2,7]dodec-2(7)-ene), the bis-endoperoxide 16 (15,16-dimethylidene-4,5,11,12-tetraoxatetracyclo[6.6.2.0^2,7.o^9,14]hexadeca-2(7),9(14)-diene), and the tris-endoperoxide 19 (4,5,11,12,17,18-hexaoxapentacyclo[6.6.6.0^2,7.0^9,14.0^15,20]icosa-2(7),9(14),15(20)-triene). The endoperoxides 11, 16 , and 19 were formed in the presence or in the absence of a dye sensitizer. The sensitized photo-oxidations of 2,3,5,6-tetramethylidenebicyclo[2.2.2]octane ( 4 ), 5,6,7,8-tetramethylidenebicyclo[2.2.2]oct-2-ene ( 5 ), 2,3,5,6-tetramethylidenebicyclo[2.2.1]-heptane ( 7 ), and 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane ( 8 ) gave successively the corresponding mono-endoperoxides 9, 10, 12 , and 13 and the bis-endoperoxides 14, 15, 17 , and 18 , respectively. Low-temperature NMR spectra of the bis-endoperoxides 14 and 16 indicated that their C₂ and C_s conformers have the same stability. Similarly, there was no difference in the enthalpy of the D₃ and C₂ conformers of the tris-endoperoxide 19 . The following reactivity sequence was observed for the sensitized photo-oxidations of 6–8 and 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene ( 23 ): 6 + ¹O₂→ 11 > 7 + ¹O₂→ 12 > 8 + ¹O₂→ 13 > 23 + ¹O₂→ 24 , a trend parallel with that reported for the ethylenetetracarbonitrile (TCNE) cycloadditions to the same polyenes. The rate-constant ratios k₁/k₂ and k₂/k₃ for the three successive photo-oxidations of [2.2.2]hericene ( 6 ) did not differ significantly from unity, in contrast with the Diels-Alder additions of 6 . Similarly, the rate-constant ratios k₁/k₂ for the two successive photo-oxidations of tetraenes 7 and 8 were significantly smaller than those reported for the successive TCNE cycloadditions to 7 to 8 . The endoperoxide formations are not sensitive to the change in the exothermicity of the reactions but they are sensitive to the electronic properties (IP's) of the polyenes.