ON THE NOVEL FREE PORPHYRINS CORALLISTIN-B, CORALLISTIN-C, CORALLISTIN-D, AND CORALLISTIN-E - ISOLATION FROM THE DEMOSPONGE CORALLISTES-SP OF THE CORAL SEA AND REACTIVITY OF THEIR NICKEL(II) COMPLEXES TOWARD FORMYLATING REAGENTS

Reported here are the novel free porphyrins corallistin B, C, D, and E , isolated as methyl esters 2a, 3a, 4&, and 5a, respectively, from the sponge Corallistes sp. (Lithistida) collected at the basis of the sou th New Caledonian coral reef. A protocol is also established for formy lation of their Ni(II) complexes, which show a different reactivity pa ttern toward DMF/POCl3 from metal complexes of deuteroporphyrins. Toge ther with corallistin A, previously isolated as the methyl ester 1a, a nd the known deuteroporphyrin IX (isolated as 6a) also present in the sponge, the new corallistins, which may be thought to derive from prot oporphyrin via heme, account for an amazing 60 % of the EtOH extract f rom the sponge.