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 \ .
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
Novel [26]porphyrinogen~ [~I 24-28 were conveniently prepared in few steps from the pyrrole building blocks 19-23. The selectivity of the cyclization is explained by a conformational helical effect due to steric congestion of the pyrrole psubstituents. The aromaticity of the [26]porphyrins[*I 30-33, obtained e y dehydrogenation of the porphyrinogens, is evi-dent from the 'H-NMR spectra displaying 25-ppm shift differences for the inner and outer protons of the porphyrins. These pigments belong to the most intensive chromophores known so far, showing VIS absorptions at 544-550 nm with lg E values up to 5.9. Present addresses: I+] Bayer AG, D-47829 Krefeld; I++] Boehringer Ingelheim KG, D-55216 Ingelheim; I+++] Solvay Deutschland GmbH, D-30173 Hannover. pared to the formation of [ 18lporphyrinogens. A computeraided inspection[l0] of three-dimensional conformations of P-substituted vinylogous tetrapyrroles revealed an increasing support of the helical conformation B (Scheme 2) with the size of the P-substituents. Scheme 1. Porphobilinogen (1) and the biomimetic transformation of its derivative 2 to [26]porphyrinogen 4 and [26]porphyrin 3 Et Et t CH2OH Et 2 Et E t a E t NCH, H , C N~ Br, Et a E t NCH, HSCN Et \@I / / / Et Et / \ \ Et E t Et Et E t 3 4 2 Bre t / / NCH, H, CN \ NCH, H, CN \ The pyrroles 10-13 (Scheme 3) were chosen as suitable precursors to investigate steric effects on the biomimetic synthesis of [26]porphyrinogens. Three of them were syn-Novel Porphyrinoids, 15 505 Scheme 5. Preparation of the pyrrole building blocks 20-23 and the transformation of 19-23 to the [26]porphyrinogens 24-28 12 10 13 11 KOH/DMSO, CH, I 1 7 5 z 187 % 176 % 180 Z CH, 19 20 21 22 23
Selective Bromination of Eugenol -(2 refs.). -(JOUVE-NOBEL, I.; DESMURS, J. R.; NONN, A.; CHENAL, T.; 3 (1991) 1, 69-73; Cent. Rech. Carrieres, Rhone-Poulenc Rech., 69192 Saint-Fons, Fr.; EN)
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.