The identification of new bifunctional esters in the essential oil of Anthemis nobilis L., the so-called Roman Chamomile oil, was recently described by two groups of Swiss research chemists. A novel structural type of naturally occurring substances derived from 3-hydroxy 2-methylene butyric acid could be ascertained in the case of compounds A to C (figure 1). The same acid is part of a goyazensanolide derivative recently described by Bohlmann et al.
The angelate D derives from a bifunctional isoprene unit whereas the esters E to G are derivatives of C4-diols exhibiting an angelic and an isobutyric acid moiety. These acids are very typical also for a large number of mono-esters already known to occur in Roman Chamomile oil.
French authors recently presented their analytical findings on the oil using the negative chemical ionization technique in mass spectrometry. They tracked the GLC profile of the complete oil with the mass numbers of the quasi-molecular ions [M-H]- in combination with the carboxylate anion RCOO-. Thereby inter alia the presence of five esters derived from methacrylic or crotonic acid was reported, however, without giving definite structural assignments for the individual components. The same holds for eight esters of the angelate or tiglate type, respectively. We have worked in a more traditional way and wish here to present the results concerning some of these methacrylates, crotonates, angelates and tiglates. All esters mentioned by us have proved by comparison with authentic synthetically prepared samples.
