Gymnochromes

The deepwater stalked crinoid Gymnocrinus richeri contained the gymnochromes C (659) and D (660) and isogymnochrome D (661). These compounds have a helical chirality and chiral atoms in the sidechains give rise to isomers [524]. 

Fig. 26. The gymnochromes, phenanthroperylenequinone pigments from the crinoid Gymnochrinus richeri.

When the major gymnochrome B (275) was heated in pyridine at 160°C, it was partially converted into a diastereomer which exhibited a CD curve opposite in sign to that of 275. This implies that the two compounds are both configurational helixes (the configurations of the side-chain chiral centres cannot be modified by the thermal isomerization). The inversion of helicity is accompanied by a... 

The green colour of the animals suggests that the pigments are present as phenoxide salts, probably in the form of Zn complexes, while the yellow colour of the live animals suggests that the phenanthroperylenequinone system of the gymnochrome might have been formed, at least in part, by oxidation and exposure to sunlight of structurally related bianthrones or other dimeric precursors. 

At least, two other species of stalked crinoids Diplocrinus altemicirrus and Proisocrinus ruherrimus have been discovered off Tahiti and Okinawa between 1000 and 1800 m depths (Roux, 1980 Wolkenstein et al, 2009). Interestingly, Proisocrinus ruherrimus led to proisocrinins A-F, a series of brominated and sulfated anthraquinone pigments closely related to the half part of gymnochromes (Wolkenstein et al, 2009). 

De Riccardis, F., lorizzi, M., Minale, L, Ricdo, R., Richer de Forges, B., and Debitus, C. (1991a) nie gymnochromes novel marine brominated phenanihroperylene quinone pigments from the stalked crinoid Gymnocrinus richeri.J. Org. Chem., 56, 6781—6787. 

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