Natural Product Studies on the Hamigerans
This study describes the NMR-directed isolation and structural elucidation of several new and semi-synthesised compounds. Carrying on from the previous examinations on the sponge Hamigera tarangaensis undertaken at VUW resulted in the isolation of an additional seven congeners to the hamigeran family. These included three debrominated analogues (37, 60, 62), an alternative methyl ester analogue (63) and a 4-brominated analogue (64). Two structures with novel functionality were also isolated, which were found in fractions previously not investigated, the nitrile containing hamigeran R (61) and the dimer hamigeran S (65). The isolation of these novel compounds led to the proposal of a biosynthesis from a reaction with hamigeran G (40) and ammonia, similar to the previous nitrogenous hamigerans biosynthesis with amino acids. Semi-synthesis was undertaken to probe the biosynthesis of these and the other nitrogenous compounds. The results of this produced four new compounds: two imine intermediates, hamigeran G imine (66) and hamigeran B imine (70), a glycine derived hamigeran (68) and the hamigeran D epimer (69).