Ethylamine, conformation

The classical histamine receptor antagonists are stmcturaHy very similar, all being substituted ethylamines (2). Table 1 presents a member of each stmctural subclass. Presumably, the ethylamine core is needed to accomplish nonfmitfiil binding to the high affinity conformation of the receptor. 

The NMR measurements for the Schiff bases being derivatives of (R)-l-(9-anthryl)-ethylamine and 2-(2 -pyridyl or quinolyl)acetophenone [23] have revealed the presence of the rigid conformation of the enamine form.56... 

Ethylamine. All force fields (save Tripos 5.2) predict the wrong (gauche) global minimum for this molecule. However, both the experimental and calculated energy differences between the anti and gauche conformers are small. 

The conformational restrictions imposed on the indole-3-ethylamine moiety permitted retention of affinity for the 5-HT receptor but it diminished affinity for the 5-HT receptor by a factor of 1000. In two functional assays, (29) exhibited potency equal to or marginally greater than that of serotonin. Com-... 

L.A.E. BAPTISTA DE CARVALHO and J.J. TEIXEIRA DIAS, Conformational analysis of dimethylethylamine an ab initio m.o. study and comparison with ethylamine and ethylmethylamine. J. Molec. Struct. (Theochem), 282,... 

Figure 4 illustrates the "standard" model generated by CAMSEQ/M. This structure may be saved for later use, and/or be used as an input structure for a conformational study. The structure may later be used as a substructure for studying other congeners, by modifying its substituents. For example, amphetamine may easily be constructed by adding the alpha-methyl group to the ethylamine sidechain. The stereochemistry of the molecule is determined by the order of input of the substituents. 

In the case of catecholamines, the functional groups of particular interest include the nitrogen atom, the C-2 oxygen atom, the aromatic ring and the aromatic oxygen substituents (see Figures 2 and 7). For compounds I-VIII, the interatomic distances are tabulated in Table VI. These may readily be compared to the corresponding values from x-ray studies of three representative conformationally mobile phenyl-ethylamines, norepinephrine hydrochloride (IX), amphetamine sulfate (X) and mescaline hydrobromide (XI). 

When the conformation of the ethylamine side-chain with respect to the aromatic nucleus is considered as the starting-point, the dopamine molecule may exist either in a trans (extended) conformation, or in a cis (gauche) conformation. Single crystal x-ray analysis of dopamine hydrochloride indicates that the ethylamine chain is in a nearly completely extended conformation which resides on a plane almost perpendicular to the plane of the catechol ring.93... 

Studies performed by Carriedo et al. indicated that the spirocyclic phosphazene polymer 37 can adopt a helical conformation in solution.146 Yashima et al. subsequently investigated the chiroptical response of 38 (Chart 7) upon complexation with (/v)-a-phenyl-ethylamine in DMSO.147 The resulting optical rotation and its response to changes in temperature... 

The very weak agonist properties of 2-methyl-5HT (4) suggested an unfavorable Ai,3 strain interaction between the 2-methyl group and the ethylamine side chain in the conformation(s) required for 5-HT4 agonism. Such Ai 3 strain would predominate in conformers wherein Tau 1 = 180°. Figure 1 illustrates this set of conformers, wherein the side chain amino group may be positioned at rotamer sites A, B, and C [13]. 

A very large amount of NMR spectroscopic data has been collected during the year under review. The presentation of data in addition to data is now almost routine. NMR spectroscopic studies have now been presented for phosphonocarboxylic acids and their esters,some new phosphinic amides, and for Lawesson s reagent (solid and solution data). A spectroscopic study of the dimer of the nitrile oxide (401) suggested the structure (402). 1-(1-Naphthalenyl)ethylamine and ephedrine are recommended for the NMR spectroscopic determination of the enantiomeric composition of (1-aminoalkyl)-phosphonates, but of quinine and rert-butylphenylphosphinothioic acid, only the former was effective for the chiral resolution of the diethyl esters in the determination of e.e.s of (2-hydroxyalkyl)phosphonates. Conformational analyses, based on NMR spectroscopic data, have been carried out for dialkyl (2-hydroxyalkyl)phosphonates. ... 

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