摘要:

AbstractThe 2,7‐diazapyrenium group (DAP2+) combines the features of pyrene, of methylviologen, and of nucleicacid intercalators and may thus present a variety of interesting properties. The cations1and2and the bis‐diazapyrenium species3have been synthesized and shown to bind molecular anions like aromatic polycarboxylates, giving rise to pronounced shifts of1H‐NMR signals, modifications of UV/VIS absorption spectra, and quenching of fluorescence. The complexes formed probably have a face‐to‐face structure, and their stability constants are remarkably high, in particular for the bis‐diazapyrenium cation3which is susceptible to form intercalative chelate complexes such as9(logKs≈ 3 for1, up toca. 7 or more for3a). Neutral molecules like adenine are also bound, but much less strongly. Visible‐light irradiation of Me2DAP2+(1) in presence of various electron donors, such as EDTA, gives the reduced species Me2DAP+wich has been characterized by UV/VIS and ESR spectroscopy. The results indicate that Me2DAP2+(1) functions as amethylviologen analogue, photoactive in visible light. Thus 2,7‐diazapyrenium cations are attractive subunits for incorporation into macropolycyclic structures to give photo‐ and electroactive

ISSN:0018-019X    

DOI:10.1002/hlca.19870700102

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Novel Cyclosporins fromTolypocladium inflatum. The Cyclosporins K–ZThe fungusT. inflatumproduces a plethora of oligopeptides, the cyclosporins, which exhibit remarkable biological activities. Cyclosporin A, the main metabolite, represents a potent immunosuppressant which opened new ways in the immunotherapy of bone marrow and organ transplantations. In addition to the already described cyclosporins A–I, we report now the isolation of the cyclosporins K–Z. The structural assignments of these novel congeners are based on chemical degradation, correlation reactions, mass spectra, and extensive analysis of1H‐ and13C‐NMR spectra. All cyclosporins are cyclic undecapeptides differing from each other by minor variations in the amino‐acid sequence. Comparison of the immunosuppressive and antifungal effects furnished new information concerning structure‐activity

ISSN:0018-019X    

DOI:10.1002/hlca.19870700103

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe thermolysis of the steroidal 5α,8β‐peroxide1, under acidic conditions afforded in addition to the expected 5,10:8,9‐diseco derivative2, the rearranged 5α,8β‐epoxide3, the structure of which was determined by NMR spectroscopy and X‐r

ISSN:0018-019X    

DOI:10.1002/hlca.19870700104

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractTwo CH3groups at C(6) of 2‐exo‐ (10a) and 2‐endo‐norbornylp‐toluenesulfonate11alower their solvolysis rates in 80% EtOH by factors of 28 and 16, respectively. A spirocyclopropyl group including C(6), as in21aand22a, reduces the rate ofexo‐ andendo‐ionization by factors of 250 and 8, respectively. The geminally dimethyl‐substituted tosylates10aand11ayield the 2‐exo‐alcohol10b, whereas the spirocyclopropyl‐substituted tosylates21aand22afurnish rearranged 3‐brendanol23. These findings are readily rationalized by the inductive model, according to which norbornyl cation formation is controlled by the inductive effect

ISSN:0018-019X    

DOI:10.1002/hlca.19870700105

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Nonapentafulvalene(1) has been prepared by oxidative coupling of sodium cyclopentadienide (6) and sodium cyclononatetraenide (7) with CuCl2in THF, two‐fold deprotonation of cyclopentadienyl‐cyclononatetraene8to give dianion16, and oxidative treatment of16with CuCl2(Schemes 2and3). Compound1is a highly reactive and thermally instable molecule, since valence isomerisation1→17proceeds easily even at low temperature (the half‐life of1isca.30 min at −15° in CDCl3). NMR investigations show that nonapentafulvalene is an olefinic molecule with strongly alternating bond lengths, its nine‐membered ring deviating strongly from planarity. Comparison of the NMR data of1with those of a series of sterically similar pentafulvenes18and nonafulvenes19(Tables 1and2) demonstrates that (a) with regard to the pentafulvene unit of1, the cyclononatetraene ring acts as very weak electron‐donating group, while (b) with regard to the nonafulvene unit of1, the cyclopentadiene ring acts as weak electron‐accepting group. So nonapentafulvalene may be regarded as a ‘nonafulvene of inver

ISSN:0018-019X    

DOI:10.1002/hlca.19870700106

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractHeptamolybdate‐ion(HM)‐catalyzed C(2) epimerization of D‐glucose and racemization of D‐glyceraldehyde proceed with comparable rates and activation parameters; HM catalyzes the isomerization of glucal and galactal triacetates as well. For all of the above transformations, a common, new mechanism is proposed that invokes stabilization of 3‐oxa‐allylic cation species by the central

ISSN:0018-019X    

DOI:10.1002/hlca.19870700107

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe alcyonaceanAlcyonium( =Parerythropodium)coralloides(PALLAS1766) is the first Mediterranean organism shown to contain cembranoids. These are of unusual type like coralloidolide A ( = (−)‐(1R*, 2R*, 3R*, 12S*, 5Z, 7Z, 9Z)‐1, 2:7, 10‐diepoxy‐12‐isopropenyl‐5, 9‐dimethylcyclotetradeca‐5, 7, 9‐triene‐1, 3‐carbolactone; (−)‐6) and coralloidolide B ( =(−)‐(1R*,2S*,3R*,7S*,10S*,12S*,5Z,8Z,)‐2, 7:7, 10‐diepoxy‐1, 10‐dihydroxy‐12‐isopropenyl‐5, 9‐dimethylcyclotetradeca‐5,8‐diene‐1,3‐carbolactone; (−)‐8). Structural assignments are mainly b

ISSN:0018-019X    

DOI:10.1002/hlca.19870700108

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe stereoselective synthesis of the major oxygenated metabolites oftrans‐sobrerol (1) in optically active and/or racemic form is describe

ISSN:0018-019X    

DOI:10.1002/hlca.19870700109

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe radical anion of 1,2:9,10‐dibenzo[2.2]paracyclophane (3) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck‐benzene rings, and of the four inner and four outer protons in the side‐benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2‐dimethoxyethane; counterion: K+). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane (1) points to similar nodal properties of the singly occupied orbitals in\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}. Notwithstanding this similarity,\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}seems to associate less readily than\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}with alkali metal counterions, since tight ion pairs of\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}with K+are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane‐1,9‐diene (2), are not apparent for\documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative4which has a CH3substituent in one of the side‐benz

ISSN:0018-019X    

DOI:10.1002/hlca.19870700110

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

New Iridoid Glycosides and a Monoterpene Glycoside fromSambucus ebulusL. (Caprifloiaceae)From the roots ofSambucus ebulusL., two novel valeriana‐type ester iridoid glycosides, 6′‐O‐apiosylebuloside (1) and 7,7‐O‐dihydroebuloside (3), along with the open‐chain monoterpene glycoside5were isolated. Their structure elucidation is based mainly on one‐ and two‐dimensional NMR methods.1H,1H‐COSY experiments permitted complete assignment of signals arising from the disaccharide unit in1. Biogenetically,3seems to represent the equivalent of loganin in the valeriana‐type series

ISSN:0018-019X    

DOI:10.1002/hlca.19870700111

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY