Subscribe to RSS
The first enantiomeric discorhabdin alkaloids and determination of absolute configuration using TDDFT calculations of electronic circular dichroism data
The discorhabdins are a class of pyrido[2,3-h]pyrrolo[4,3,2-de]quinoline tetracyclic skeleton-containing cytotoxic alkaloids isolated from marine sponges of the families Latrunculiidae and Acarnidae . While the absolute configuration of prianosins A – D have been established, the configuration of the remaining thirty-odd alkaloids in this family are undefined. As part of a survey of New Zealand Latrunculia spp. sponges, we have isolated the first examples of enantiomeric pairs of discorhabdins B, G*/I, L and W. The absolute configuration of all four compounds has been secured by comparison of observed experimental data with the results of time dependent density functional theory (TDDFT) calculations of electronic circular dichroism spectra. The absolute stereochemistry of a number of related discorhabdins and new natural products has been established upon comparison with the calculated spectra. The results of this study provide a baseline dataset that should enable the definition of absolute configuration of any thioether-containing discorhabdin alkaloid.
Acknowledgements: We thank Dr V. Webb (NIWA, NZ) for supply of sponge specimens.
References: 1. Antunes, E. M. et al. (2005) Nat. Prod. Rep. 22:62–72.