Isolation and Total Synthesis of PM170453, a New Cyclic Depsipeptide Isolated from sp.

In our continuing search for biologically active new chemical entities from marine organisms, we have isolated a new cyclic depsipeptide, PM170453 (), from a cyanobacterium of the genus sp., collected in the Indo-Pacific Ocean. Structure elucidation of the isolated compound was determined by spectroscopic methods including MS, H, C and 2D-NMR. To solve the supply problem for and progress pharmaceutical development, the total synthesis of that involves a total of 20 chemical steps in a convergent process was carried out. Its in vitro cytotoxic activity against four human tumor cell lines, as well as the inhibition of the interaction between the programmed cell death protein 1 PD-1 and its ligand PD-L1 were also evaluated.