摘要:

Macrocyclic Benzolactones by Ring Enlargement of 2‐NitrocycloalkanonesReaction of 2‐nitroalkanones with 1,4‐benzoquinone in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐en gave (hydroxybenzo)nitrolactones of general formula6(Scheme 1). The transformation involves aMichaelreaction, aromatization, and ring enlargementviaa five‐membered intermediate. The (hydroxybenzo)nitrolactones were converted to the already known (acetoxybenzo)oxolactones15–17. The characteristic mass spectral behavior of the ring‐enlarged prod

ISSN:0018-019X    

DOI:10.1002/hlca.19860690112

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractFour new halogenated chamigrenes have been isolated from the sea hare, the (E)‐ and (Z)‐9‐(bromomethylidene)‐1,2,5‐trimethylspiro[5.5]undeca‐1,7‐dien‐3‐ones (11and10, resp.) the structures of which were deduced by NMR spectroscopy and by comparison with a known relative, the (8R,9R)‐8‐bromo‐9‐chloro‐5,5,9‐trimethyl‐1‐methylidenespiro[5,5]undec‐3‐en‐2‐one (12), and its (11R)‐11‐acetoxy‐substituted derivative13. Their structures and absolute configurations were determined and deduced by X‐ray using the absolute‐structure parameter. The configurations were remarkable in being enantiomeric to those of the tertiary chlorochamigrenes isolated so far. Consequently, a more general

ISSN:0018-019X    

DOI:10.1002/hlca.19860690113

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Optically Active Lycopene Epoxides and Lycopene Glycols: Synthesis and Chiroptical PropertiesWe present extensive spectral and chiroptical data on the pure and crystalline lycopene diepoxides1–3and glycols4–9. A first synthetic approach to1–9with (+)‐malic acid as starting material afforded30as a complex mixture of isomers (Scheme 1). Pure stereoisomers1–9were obtained using the enantiomerically pure epoxygeraniol31as starting material (Scheme 2). Differentiation of the (5Z)‐from the (all‐E)‐isomers by1H‐NMR and UV/VIS alone

ISSN:0018-019X    

DOI:10.1002/hlca.19860690114

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Abstract1H‐ and13C‐NMR spectra of a series of nonafulvenes1have been investigated. Most nonafulvenes are olefinic molecules with alternating bond lengths, their nine‐membered ring deviating strongly from planarity. The 10‐monosubstituted nonafulvenes contain 2 sterically different ring segments with a nearly planar (E)‐diene system consisting of C(7), C(8), C(9), C(10), and R. Substituents R are influencing C(9)>C(7)>C(5). In symmetrically substituted nonafulvenes a fast process equilibrating olefinic conformers is operating so that pairs of ring protons and ring C‐atoms are equivalent and only average substituent effects are observed for C(9)>C(7,2).1H‐ and13C‐NMR chemical shifts are not significantly influenced by changes of solvent or temperature. On the other hand, new13C‐ and1H‐NMR experiments completing previous investigations byHafnerandTappeconfirm that NMR spectra of 10,10‐bis (dialkylamino)nonafulvenes are strongly dependent on solvent polarity and temperature. At ambient temperature and in unpolar solvents, nonplanar conformers are predominant, their spectral data fitting into the series of other nonafulvenes. At low temperature and/or in polar solvents, dipolar conformers are favoured which are characterised by charge separation and a planarised (but not necessarily completely planar) nine‐membered ring with negative excess charge. The spectroscopic behaviour of nonafulvenes is reasonably explained by a qualitative scheme (Fig. 7) which is based on a model proposed byBo

ISSN:0018-019X    

DOI:10.1002/hlca.19860690115

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractThe15N‐NMR spectra ofcis‐ andtrans‐2,3‐dialkyl‐substituted triaziridines are reported. The assignment of the15N‐NMR resonances is described, and the chemical‐shift and coupling data are compared with those of aziridines and diaziridines. The1J(N,H) coupling constants allow one to deduce the relative configuration of the involved N‐atom. In CDCl3, a1J(N,H) value of 58.1 ± 0.5 Hz is assigned to an NH bondcisto two lone‐pairs of electrons at neighboring N‐atoms,i.e.to thecis,trans‐triaziridinesThe first stereodescriptor denotes the relative configuration of the two equal alkyl substituents, the second the relative configuration of one alkyl substituent and the H‐atom., and a value of 51.7 ± 0.5 Hz is assigned to a NH bondcisto only one lone‐pair of electron

ISSN:0018-019X    

DOI:10.1002/hlca.19860690116

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractHyperfine data andgfactors are reported for the radical cations of tetrathiafulvalene (TTF;1) and of its derivatives2–13. From the intense satellite spectra of1+–13+not only the coupling constants of the33S isotopes in the TTF moiety could be determined, but also, in favourable cases, those of the13C isotopes in the central double bond. The former values range from 0.370 (8+) to 0.470 mT (4+) and the latter from 0.255 (8+) to 0.360 mT (4+) in the radical cations of bis(ethylenedithio)‐TTF (8+) and tetracyano‐TTF (4+). The radical cation of TTF (1+) exhibits intermediate values, 0.425 for the33S and 0.285 mT for the13C isotopes. The spin population in1+–13+resides, to a large extent, in the central S2C  CS2part of the π‐system. It tends to increase (decrease) by substitution with electron‐accepting (donating) groups in the 2,3,6,7

ISSN:0018-019X    

DOI:10.1002/hlca.19860690117

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractReactions carried out on benzoyl (2) and hydroxybenzyl (10) derivatives ofL‐phenylalanine‐cycloanhydride1lead to the conclusion that the structure3, previously proposed for picroroccellin (a metabolite from the lichenRoccella fuciformis), should be revised to6, While the FeCl3‐catalyzed photo‐oxidation of1gives2, theN,N′‐dimethyl derivative7leads toN,N′‐dimethyl‐2‐benzylpiperazine‐3,5,6‐trione (9).N,N′ ‐diacetyl‐L‐phenylalanine‐cycloanhydride11remains unchanged. It is established thatN,N′ ‐substitutions of 2,5‐dibenzylpiperazines‐3,6‐diones considerably influence their pho

ISSN:0018-019X    

DOI:10.1002/hlca.19860690118

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

A Novel Ester Iridoid Glucoside fromSambucus ebulusL. (Caprifoliaceae)A novel ester iridoid glucoside, ebuloside (1,), which shows structure elements of the rare 7‐Dehydrologanin derivatives combined with those of theValerianaceaeiridoids, was isolated from the roots ofSambucus ebulusL. Its structure was determined by MS, NMR, and CD spectroscopy as 7‐oxo‐8‐deoxyvalero

ISSN:0018-019X    

DOI:10.1002/hlca.19860690119

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractConformational factors have been found responsible for the dramatic change in odor between (−)‐deoxyambreinolide (12) and its (+)‐epi derivative13. The presumably molecular event during the receptor interaction has been simulated by the diastereoisomeric 11‐methyl‐ambroxderivatives3and5as model

ISSN:0018-019X    

DOI:10.1002/hlca.19860690120

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

Addition Reaction of 1,3‐Thiazole‐5(4H)‐thiones and Ynamines; Formation of Thioamides and ThioketonesYnamines and 1,3‐thiazole‐5(4H)‐thiones of type1undergo an addition reaction on heating in toluene yielding mainly α,β‐unsaturated 2‐(4,5‐dihydro‐1,3‐thiazol‐5‐yliden)thioamides of type7(Scheme 2andTable). In some cases, 1‐diethylamino‐1‐(4,5‐dihydro‐1,3‐thiazol‐5‐yliden)‐2‐alkanethiones8have been isolated as minor products. In analogy to other reactions of ynamines with CO and CS bonds, a [2 + 2] cycloaddition to thiete intermediates, followed by an electrocyc

ISSN:0018-019X    

DOI:10.1002/hlca.19860690121

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY