Tolytoxin and new scytophycins from three species of Scytonema.

Tolytoxin [1], the major cytotoxin associated with Scytonema mirabile strain BY-8-1, Scytonema burmanicum strain DO-4-1 and Scytonema ocellatum strains DD-8-1, FF-65-1, and FF-66-3, has been shown to be 6-hydroxy-7-O-methylscytophycin B. Minor amounts of three other new cytotoxic scytophycins, 6-hydroxyscytophycin B [2], 19-O-demethylscytophycin C [3], and 6-hydroxy-7-O-methylscytophycin E [4], have also been isolated from these cyanophytes. The gross structures and stereochemistry are based on nmr and cd analysis and on comparison with scytophycins A-E.