Malbrancheamide B, a novel compound from the fungus Malbranchea aurantiaca1

¹Taken in part from the PhD thesis of M. Figueroa.

Abstract

A new indole alkaloid, namely malbrancheamide B (2), was isolated from the culture medium and mycelia of the ascomycete Malbranchea aurantiaca along with malbrancheamide (1). Structural elucidation of 2 was carried out by a combination of mass spectrometry (MS) and ¹H and ¹³C NMR spectroscopy analyses, as well as by comparison of the NMR data with those of 1. According to the conformational studies using molecular mechanics analyses, compound 2 exists in one preferred conformation, which was optimised by density functional theory (DFT) calculations. Compound 2 is the second chlorinated indole alkaloid possessing a bicyclo [2.2.2] ring with an unusual relative configuration at C12a in the bicyclo [2.2.2] diazaoctane ring system. So far, these structural features seem to be unique for the alkaloids biosynthesised by the fungus M. aurantiaca.

¹Taken in part from the PhD thesis of M. Figueroa.

Keywords:

• Malbranchea aurantiaca
• Malbrancheamide
• Malbrancheamide B

Acknowledgements

This work was supported by grants of Facultad de Química and CONACyT 45814-Q. We are also grateful to the following people: Rosa Isela del Villar, Marisela Gutierrez, and Georgina Duarte for recording NMR, UV, IR, and mass spectra; and Isabel Rivero-Cruz and Laura Acevedo for technical assistance.

Notes

¹Taken in part from the PhD thesis of M. Figueroa.