Musca-aurin

Of particular interest was the discovery of the fost two pigments. Musca-aurin I, containing a residue derived from ibotenic acid, was found to be absent in the edible Amanita caesarea, which is also devoid of this hallucinogenic amino acid although it contains all of the remaining pig-... 

Fig. 4. Structures of musca-aurins, where R is a betalamic acid residue. The musca-aurin of which the pigment is composed is specified in parentheses.

The structure of all musca-aurins has been confirmed by a partial synthesis using an appropriate amino acid and betalamic acid derived in situ from betanine in the presence of aqueous ammonia (Scheme 20). The transi-mination equilibrium was displaced toward the desired product by using a 5- to 10-fold excess of the amino acid. The progress of the reaction was monitored spectroscopically, following the change of absorption intensity at 540 and 475 nm (69). 

The isolation and identification of the light, acid, and base sensitive musca-aurins posed considerable separation problems which were overcome by careful, repeated chromatography on Sephadex 188, 192). Hydrolysis of the individual musca-aurins gave betalamic acid (174) together with the constituent amino acids which were detected by electrophoresis and paper chromatography and identified by linked gas chromatography-mass spectrometry of their 7V-trifluoroacetyl methyl esters 189,192). 

Musca-aurin Amino Acid Component Name of Betalaine... 

Musca-aurin-V Glutamine Asparagine Leucine Valine Vulgaxanthin-II 529)... 

Musca-aurins-III and -IV also contain a novel dehydroglutamic acid component. 

The composition of each of the musca-aurin betalaines was confirmed by partial synthesis from the appropriate amino acid and beta-lamic acid derived in situ from betanin (178), a pigment of the red beet, Beta vulgaris. The equilibrium depicted in Scheme 32 was monitored spectrophotometrically and the musca-aurins thus produced were purified by Sephadex chromatography 189). 

Dopp, H., S. Maurer, A.N. Sasaki, and H. Musso Fliegenpilzfarbstoffe VIII. Die Konstitution der Musca-aurine. Liebigs Ann. Chem. 1982, 254. 

---