G. G. Trigo

Synthesis and structural study of N-ethylnortropane-3-spiro-5′-oxazolidine-2′,4′-dione and its hydrochloride

Abstract N (8)-Ethylnortropane-3-spiro-5′-oxazolidine-2′-4′-dione hydrochloride has been synthesized and its crystal and molecular structures determined by X-ray diffraction. IR, Raman, 1 H NMR and 13 C NMR methods. It is found that the crystalline structure is maintained in D 2 O solution. In D 2 O solution a protonation equilibrium takes place and the percentages of the two isomers are calculated. In order to correlate the results, analogous spectroscopic measurements have also been made for the N -ethylnortropane-3-spiro-5′-oxazolidine-2′,4′-dione, for which a zwitterionic structure is deduced.

Structural and conformational study of ortopramides derived of the tropane system

Abstract Several 3(substituted benzamido)N-substituted-nortropane compounds have been synthesized and their molecular structures determined by IR, 1 H NMR and 13 C NMR methods. From the IR data a molecular association was deduced for these compounds in the solid state. From the 1 H NMR and 13 C NMR, the following general features were deduced: All compounds studied adopt a slightly flattened chair conformation in CDCl 3 or DMSO solution. In all cases, only the epimer with the amido group in the exo position was isolated.

3-Aminotropane-3-carboxylic acids. Preparation and properties

The two isomers of 3-aminotropane-3-carboxylic acid have been prepared by hydrolysis of the two α- and β-tropane-3-spiro-5′-hydantoins whose configurations were determined by X-ray crystallography and 13C nmr. The values of these amino acids and the hydrolysis rates of their N-formyl derivatives have been determined to study the influence of the amino group in an axial or equatorial position. The biological transport – inhibitory action of the two tropane amino acids has also been compared.

N-substituted granatanine-3-spiro-5′-hydantoins as zwitterions. Potentiometric determination of the pK1 and pK2 values for the conjugate acids

Remarkable pK1, and pK2 values for N-substituted granataninespirohydantoins which have the zwitterion structure (II) have been found by potentiometry. Previously proposed conformations for the conjugate acids (H2Z+) and the zwitterion forms (HZ+–) may explain these values.

Infrared and 1H NMR structural study of 3-tropane, 3-granatane and 3-bicyclo(3.2.1)octane epimeric amino acids

Abstract Five amino acids with known configuration: α- and β-3-amino-tropane- and 3-amino-bicyclo(3.2.1)octane-3-carboxylic acids and α -3-amino-granatane-3-carboxylic acid have been studied by i.r. and 1 H NMR spectroscopy. Both α- and γ-zwitterion structures have been found for tropane and granatane amino acids. Equatorial and axial ammonium groups in α-zwitterions can be distinguished by the number and frequencies of the ammonium deformation modes. A chair—boat conformation has been deduced for α-3-amino-granatane-3-carboxylic acid.