The Cylindrospermopsin Alkaloids - Literature review Example

The cylindrospermopsin alkaloids of cylindrospermopsin (1), 7-deoxy-cylindrospermopsin (2), and 7-epi-cylindrospermopsin (3). II. Isolation and Characterization Cylindrospermopsin (1), was extracted in 1992 from the cyanobacterium Cylindrospermopsis raciborskii and characterized by Moore and co-workers.

The characterization was done using a combination of NMR and mass spectroscopy. (Ohtani, Moore and Runnegar, 1992) In 1999 during routine purification of cylindrospermopsin using HPLC 7-deoxy-cylindrospermopsin (2) was discovered and characterized (Norris, et al., 1999). It was also believed that the newly discovered cylindrospermopsin derivative could exist in the form of two tautomers. The conclusion was drawn from the fact that the vinylic proton of the uracil ring was not detected using the 1H NMR technique (Figure two).

However, the presence of the uracil group in (4) was proven by investigating the absorbance maximum (?max) that was observed for every sample of 7-deoxy-cylindrospermopsin (2). It was obvious that the natural material existed as a mixture of compounds but it was not possible to estimate the quantity of (2) (Looper, et al., 2005). Figure two. Proposed tautomeric forms of 7-deoxy-cylindrospermopsin (2). Discovered in 2000, 7-epi-cylindrospermopsin (3) initially was found to be synthesized by Aphanizomenon ovalisporum (Banker, et al., 2000). Taking into account the unusual tautomer enol existence of the uracil D ring, estimation of the relative stereochemistry of cylindrospermopsin (1) was made.

The uracil D ring was intramolecularly hydrogen attached to a nitrogen terminus of the guanidine group as described in structure 6. The produced configuration was in correlation with the NMR evidence which led the research group to structure 7 as the most likely description of cylindrospermopsin (1) (Figure three) (Heintzelman, et al., 2001). The correct stricture for cylindrospermopsin (1) and its epimer, 7-epi-cylindrospermopsin (2), was deduced by thinking about these alkaloids as uracil tautomers (Figure one).