Pyrrolizidine triols

Eight esters of crotanecine (17) have been characterised (Table 3 S) by CuLVENOR et al. (22,93). The similarity of the n. m. r. and mass spectra of 

As part of their extensive chemotaxonomic studies on the Compositae, Bohlmann etal (39—45) have recently discovered several new types of pyrrolizidine alkaloids with a dihydropyrrolizine nucleus in Senecio species. These are all neutral compounds. The senampelines, which occur as isomeric mixtures that have not yet been separated, contain the triol (19) of unidentified stereochemistry (Table 3T). Another series of compounds contains the related oxidised dihydropyrrolizinone (20) which occurs naturally with either 7 a or 713 stereochemistry as part of the macrocyclic diester system (Table 3U). 

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