The cowr picture shows ii schematic representation of the arrangement in a crystal that resembles a tartan. I t i s the expected structure for the 1 :1 adduct formed betwcen ;I tetracationic cyclophane and ferrocene (green). The cyclophane was designed t o permit recognition both in an external and internal fashion. Indeed, the cyclophaiic Ibrms sheets and channels in the solid state through external recognition betwen i1.s conhtituent components. The cyclophane also complexes substrates such ;IS fcrrocenc ~i t h i n i t s cavitj predicted, whilst retaining the ability to form highly structured three-dimensional arrays. in common with the free cyclophane. Stoddart et d . LIX I .3-bis(2-bromoethoxy)ben~eiie (red) and bipyridine (blue) as building blocks t o ahsemble the desired tetracationic cyclophane. More about the free cycloplianc and i t s 1 : 1 fei-rocene adduct --esamples of "molecular mosaics"-are reported on p. 1802 fl'. REVIEWS ContentsExtremel) high intensity pigments with extinction coefficients up to 50 times larger than that o f the industrially important pigment indigo are the red t g n -. the violet 26 n-. and the blue 34n-porphyrins shown below. For these porphyrins a linear relationship exists between the wavelength of the most intense Soret band and the number o f 7t electrons in the iiiacro le. With syntheses based o n those in nature. :I Iai-gc niimbcr of expanded. bridged. inverted. and N-substituted porphyriii derivat i b e z is accessible with interesting properties for chemical and medicinal applicat I on \ .

A solution of 3a (0.9 g, 6.1 mmol) in toluene (40 mL) was treated at -50°C with 4 m L of a solution of tris(ethene)nickel in toluene (2.0 mmol Ni(C2H4)?; titer determined by reaction with P(OCH,), and 1,5-cyclooctadiene). The stirred mixture was allowed to warm to room temperature in 30 min and the solvent was then removed under vacuum. At 45OC/IO-' torr, light green 4a sublimed, which is colorless in thin layers (75 mg, 0.19 mmol, 12.5%). MS: m / z 403

Phorochem. Photohiol. 44 (1986) 5 5 5 ; E. Vogel, M. Kocher, M. Balci, I. Teichler. J. Lex. H. Schmickler, 0. Ermer, Angew. Chem. 99 (1987) 912; Angew. Chem. Int. Ed. Engl. 26 (1987) 931; B. Wehrle, H.-H. Limbach, M. Kocher. 0. Ermer, E. Vogel, ihid. 99 (1987) 914 and 26 (1987) 934; H. (Universitlt Heidelberg) for performing these calculations.[8] In the case of the porphycene parent compound, reaction with bromine also leads exclusively to P-pyrrolic bromination, but the bromine substituent is found in the 2-position, which is occupied by a propyl group in 5. 2-Bromoporphycene is the only isolated monobromination product (unpublished results with K . Pramod and H.-J. Dunnwuhf). This substitution pattern for bromination is different from that of porphyrin, for which regioselective substitution at the methine bridge leads to the formation of 5-bromoporphyrin [H.

Telefax: Int. + 2151188-7703 rechtfertigt, sie als Porphyrinoide zu bezeichnen, da sie alle aus einer gemeinsamen Biosynthesevorstufe, dem Uroporphyrinogen I11 3, hervorgehen (Schema l)L5-']. CO, H CO, H 1 2 Porphyrin Porphyrinogen COaH 3 Uroporphyrinogen 111 Schema 1. Strnktur der Porphyrinoide 1-3. Fur die Bedurfnisse der Organismen entwickelte die Natur eine Bioproduktion von Porphyrinoiden, deren Dimensionen abgeschatzt werden konnen. Beginnen wir mit dem Porphyrinoid Vitamin B,, , dessen Mange1 perniciose Anamie verursacht. Der Mensch benotigt nur die auI3erordentlich geringe Menge von taglich 0.001 mg Vitamin BIZ; das ergibt fur die gesamte Erdbevolkerung einen Jahresbedarf von etwa 2000 kg. Der zur

In addition to the well known alkaloids, ergot contains two groups of yellow to red pigments, between which there is a close and novel biogenetic relation. The pigments are anthraquinonecarboxylic acids and dimeric hydroxanthone derivatives (ergochromes), the structures of which, including the absolute configurations at 80 centers of chirality, have been completely determined. The intermediates involved in the biosynthesis have been largely established by feeding with labeled precursors, and its course by model experiments.

Aus Roggenmutterkorn wurden drei hellgelbe Farbstoffe, die Secalonsauren A, B und C isoliert. Sie haben die Summenformel C32HJOO14 und sind diastereomer. In Verbindung mit fruheren Ergebnissenlo) wurden durch Ozonabbau, Massen-und NMR-Spektren sowie Rotationsdispersion die vollstandigen Strukturen der drei Farbstoffe einschliefilich der absoluten Konfigurationen an ihren sechs Asymmetriezentren zu 4, 5 und 7 festgelegt. Systematik der Mutterkorn-FarbstoffeDer auf Roggenahren wuchernde Mutterkornpilz Claviceps purpurea bildet hellgelbe Farbstoffe, deren Strukturen einen neuartigen Biosyntheseweg vermuten lassen. Diese Farbstoffe enthalten das Grundgeriist 3, welches sich formal vom Anthrachinon (1) durch oxydative Ringoffnung (2) und anschlieoenden Xanthon-RingschluB ableitet und somit ein Seco-anthrachinon (3) darstellt. Es ist moglich, daB auch dessen Biosynthese auf diesem Wege aus einem Anthrachinon oder einer ahnlichen Biosynthesevorstufe erfolgt (1 -3). Hierfur sprechen neuere biogenetische Erkenntnisse4) und das Auftreten der Anthrachinon-carbonsauren Endocrocins) und Clavorubin 5.6) im Mutterkorn.AuBer dem von WhuI/ey u. a. 7) aufgekliirten Ergoflavin (6) isolierten wir aus Mutterkorn verschiedener Herkunft erstmalig die drei diastereomeren Hauptfarbstoffe Secalonsaure A, B und CS99,1-3), die diastereomeren Ergochrysine A und B1-3), 1' IX.

No abstract

Uroporphyrinogen 111 plays a key role in the biosynthesis of heme, the red pigment of blood. In uiuo studies with specifically I4C-and 3H-labeled precursors have revealed that the formation of uroporphyrinogen I11 in the organism follows several primary and subsidiary pathways. Model experiments on the pattern of biosynthesis have led to simple and effective methods of synthesizing uroporphyrin analogs and have shown that their production is strongly favored thermodynamically. The biologically important porphyrins thus available permit a mechanistic explanation of the light-induced dermatoses in porphyria diseases and suggest promising medical applications in diagnosis and therapy.