Latrunculins: NMR study,two new toxins and a synthetic approach

A complete ¹H and ¹³C NMR assignment of one of the latrunculins (B) was accomplished with the aid of 2D NMR COSY and CH shift-correlation experiments. The various H-H Coupling constants have been datermined and a conformation of the macrolide and the tetrahydropyran (THP) ring suggested on basis of the J-values and measured NOE's. The absolute configuration of latrunculin-A($\text{1}$) was determined on the grounds of its earlier X-Ray analysis, and a chemical degradation to a known compound. Two novel latrunculins, -C($\text{3}$) and -D($\text{4}$), were isolated from the Red Sea sponge $\text{L. magnifica}$ and their structures elucidated. Starting with L-cysteine a synthon for the latrunculins has been synthesized.