Showing papers on "Bicyclic molecule published in 1970"

Carbon-13 chemical shifts of bicyclic compounds

Abstract: 13C NMR absorption spectra of 50 bicyclic hydrocarbons, alcohols and ketones have been measured, in addition to some terpenes. The 13C chemical shifts are approximately additive for similar compounds and can be used for the determination of molecular structure; they differ for endo- and exo-isomers, just as in proton spectra. These quite regular and predictable 13C shift differences are much larger and are caused by the 1,4-nonbonded interaction between atoms heavier than hydrogen, not by magnetic anisotropy effects.

Additions to bicyclic olefins. III. Stereochemistry of the epoxidation of norbornene, 7,7-dimethylnorbornene, and related bicyclic olefins. Steric effects in the 7,7-dimethylnorbornyl system

Abstract: A systematic study of addition reactions of norbornene, 7,7-dimethylnorbornene, and related bicyclic olefins has been undertaken in order to define more precisely the role of steric effects in controlling the stereo- chemistry of the additions and the nature of the intermediates in such addition reactions. The addition of borane to norbornene proceeds almost exclusively exo (99.573, whereas the corresponding addition to 7,7-dimethylnor- bornene proceeds preferentially endu (78%). Similarly, hydroboration of 2methylenenorbornane gives pref- erentially exo (85%), whereas 2-methylene-7,7-dimethylnorbornane gives preferentially (85%) endo product. Similar results were realized with 1-methylnorbornene, 2-methylnorbornene, bornene, and 2,7,7-trimethylnorbor- nene. Consequently, hydroboration of norbornene, 1- and 2-methylnorbornene, and 2-methylenenorbornane goes predominantly exo, evidently reflecting the greater steric availability of the exu position in this bicyclic system. However, the presence of 7,7-dimethyl substituents causes the addition to proceed preferentially from the endu direction. Consequently, in hydroboration the 7,7-dimethyl substituents alter the normal direction of addition to olefins of the norbornane structure, irrespective of whether the double bond is endocyclic, directly under the 7,7- substituents, or exocyclic, located to the side of the substituents. major argument for the u-bridged norbornyl cation A is the almost exclusive exo substitution realized in the solvolysis of 7,7-dimethylnorbornyl derivatives. 334

S,S'-Bis-cyclo-gylcyl-L-hemicystyl-glycyl-glycyl-L-prolyl, ein künstliches, bicyclisches Peptid mit Kationenspezifität.15. Mitteilung über homodet cyclische Polypeptide†

Abstract: Using only amino acids occurring in proteins it should, in principle, be possible to synthetize peptide molecules capable of complexing metal cations. The approach described in this contribution is to build cages of oxygen atoms that could contain A-cations of specific diameter (in a manner similar to nigericin, nonactin, valinomycin, and other antibiotics) by binding together face-to-face and in the correct distance from one another two homodetic cyclic peptide rings. Using a link that may be formed and broken in a reversible manner (for example oxidativeformationon the outside of the cell membrane and reductive cleavage on the inside), one should even be in a position to construct a model for active, energy-coupled transport of cations across the cell membrane. An example of this type of synthetic products is the bicyclic peptide S, S′-bis-cyclo-glycyl-L-hemicystyl-glycyl-glycyl-L-prolyl. This compound, the first to contain two homodetic peptide rings bound together, was prepared by stepwise synthesis from the C-terminal of the S-protected pentapeptide active ester, glycyl-(S-diphenylmethyl)-L-cysteyl-glycyl-glycyl-L-proline-p-nitro-phenyl ester, using active esters of protected amino acids, followed by cyclization of this inter-mediate, cleavage of the diphenylmethyl protecting group, and final oxidation of the thiol group to the disulfide function. EMF.-Measurements on membranes by Simon and Pioda according to the method of Stefanac & Simon [4] revealed cation specificity in the order: K+ > Na+ > Li+ > Ca++. Optical rotatory dispersion shows that there is a conformational transition during complexation. Circular dichroism points to a 75–90° dihedral angle and right-handed helicity of the disulfide bond. On this basis the models shown in Fig. 6 were constructed as hypothetical representations of the potassium complexes with cages of eight or of ten oxygen atoms.

Über eine ungewöhnliche Cyclisationsreaktion bei der Umsetzung von (+)‐Epoxy‐α‐dihydrojonon mit Hydrazinhydrat

Abstract: (+)-Epoxy-α-dihydroionone (2) is formed completely stereospecifically from (+)-α-ionone (1) Under the conditions of the Wharton reaction this epoxide gives the expected isomeric allyl alcohols 4 and 5 and, surprisingly, the bicyclic allyl alcohol 3 The structure and absolute configuration of the reaction products have been established A common intermediate for the formation of compounds 3, 4 and 5 is probably the vinyl anion C

Valenzisomerisierung von cis‐Dienonen, II. 5‐Phenylpenta‐2, 4‐dienaldehyde [1]

Abstract: The 5-Phenylpenta-2,4-dienaldehydes 4, and 7, show an uncatalized cis-trans-isomerization of the 4,5-double bond above 70 °C. The negative value of the activation entropy for these reactions points to the formation of the bicyclic valence isomeric 2H-Pyrans 5 and 8 respectively in the rate determining step. Intermediate 5 can be trapped as its tetracyanoethylene cycloadduct 11. The cis-trans isomeric 1,6-diphenyl-hexa-1,3,5-trienes 12a and 12b undergo above 150° a disrotatory ring closure to the bicyclic dienes 13 and 14 respectively.

Photoelectron Spectra of Bicyclic and Exocyclic Olefins

Abstract: The construction and operational characteristics of a newly built photoelectron spectrometer are described. The photoelectron spectra of some bicyclic and exocyclic olefins and related saturated hydrocarbons have been recorded and their ionization potentials reported. The lowest ionization potentials are examined and discussed in terms of substitutional and ring strain effects. Ionization potential changes accompanying substitution in these molecules are explained by using empirically generalized substitution rules for saturated and unsaturated hydrocarbons. There appear to be no significant ring strain effects upon the lowest ionization potentials of four‐, five‐, or six‐membered ring exocyclic olefins or for the bicyclic molecules norbornane, norbornene, and norbornadiene. From a comparison of the ionization potential changes between 1, 3‐ and 1,4‐dienes, it is estimated that the two double bonds in norbornadiene are directionally coupled across the ring by an interaction energy of about 0.3 eV. From an...

Dimer acid structures: Cyclic structures of clay catalyzed dimers of normal linoleic acid, 9-cis, 12-cis-Octadecadienoic acid

Abstract: The clay catalyzed dimer of linoleic acid has been examined by mass spectrometry of the unhydrogenated, the partially hydrogenated and completely hydrogenated dimer The results show that monocyclic, bicyclic and tricyclic structures are present Monocyclic structures predominate, bicyclic structures are also prominent, and tricyclic structures are relatively minor The monocyclic structure is believed to arise from a Diels-Alder type addition reaction The bicyclic structure may result from a free radical coupling followed by intramolecular ring closure The monocyclic structure in the unhydrogenated dimer appears to be mostly a benzene ring with saturated and unsaturated side-chains It probably is formed by hydrogen transfer from the Diels-Alder cyclohexene structure first formed Little, if any, of the Diels-Alder dimer structure as such is present The catalytic linoleate dimer has a higher ratio of monocyclic to bicyclic dimer than does the noncatalytic (thermal) dimer made from normal (nonconjugated) linoleate, while the thermal dimer of a conjugatedtrans-trans linoleate is exclusively monocyclic It is suggested that the clay catalyzes conjugation and hence favors the Diels-Alder reaction, and then catalyzes hydrogen transfer to aromatize the cyclohexene ring

Mass spectra of the substituted quinuclidines

Abstract: The mass spectra of the quinuclidine-2 (and -3)-ones and other functional derivatives of quinuclidine as well as 2-azaquinuclidine and benzoquinuclidine have been investigated The fragmentation through the open form of the molecular ion and the applicability of Bredt's rule to amine fragmentation of the bridgehead nitrogen bicyclic systems are discussed

Gas-phase stabilities of bicyclic cations

Abstract: Gas phase stabilites of bicyclic cations, establishing heats of formation limits by ion- molecule reactions identification

Flexional Effects in Bridged Bicyclic Molecules Progressive Flattening of Chair Cyclohexane

Abstract: Measures of the progressive flattening of the chair conformation in a series of constrained cyclohexanols are obtained and compared by proton NMR. coupling constants and by molecular mechanics.

Studies on Structure-Activity Relationship of Analgetics. X. Syntheses of 11-Amino-2, 3-benzobicyclo [3. 3. 1] nonane and 3-Phenyl-9-amino-bicyclo [3. 3. 1] nonane Derivatives.

Abstract: Some derivatives of 11-amino-2, 3-benzobicyclo [3. 3. 1] nonane and 3-phenyl-9-amino-bicyclo [3. 3. 1] nonane were synthesized from β-tetralon and 4-phenylcyclohexanone, respectively, through an enamine cyclization. Configuration and conformation of these bicyclic compounds were elucidated by nuclear magnetic resonance spectral analysis. A peculiar property, resembling to Sommelet reaction, of the amino group attached to bridged methylene in bicyclic system is presented. The mass spectra of the amino derivatives of bicyclo [3. 3. 1] nonane system are discussed.