Aromatic acids methyl esters, mass spectra

In Table IV some physical data and spectral characteristics of 6,7-secoberbines are listed. Only methyl corydalate (55) is optically active. Formula 55 presents the spatial structure of this compound, deduced by Nonaka et al. (65) and confirmed by Cushman et al. by both correlation with (+)-mesotetrahydrocorysamine (72) (<5S) and total synthesis (69). It is difficult to find common characteristic features in both the mass and H-NMR spectra of these alkaloids because they differ significantly from each other in their structures. On one hand, corydalic acid methyl ester (55) incorporates a saturated nitrogen heterocycle, while the three aromatic bases (56-58) differ in the character of the side chain nitrogen. For example, in mass fragmentation, ions of the following structures may be ascribed to the most intensive bands in the spectrum of 55 ... 

Sanchez and Brown have obtained a new harman derivative from Aspi-dosperma exalatum Monachino (121). The alkaloid was obtained from a butanol extract, and in the IR spectrum it showed principal absorptions at 1925 cm-1 for an immonium ion, at 1610 cm-1 for a carboxylate anion, and at 748 cm-1 for a disubstituted benzene. In the mass spectrum a molecular ion was observed at m/e 226 and a base peak at m/e 182 (M+ —44). An aromatic methyl group and five aromatic protons were observed in the PMR spectrum. Consideration of this data together with the UV spectrum led to deduction of the structure of the alkaloid as 268, harman carboxylic acid. The ethyl ester (269) was also isolated but it was probably an artifact. 

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