Total Synthesis of Tosyl-Samroiyotmycin A and Its Biological Profiling.

A total synthesis of the enantiopure syn,syn-tosyl-samroiyotmycin A, a C-symmetric 20-membered antimalarial macrodiolide with syn,syn-configuration of the 8,24-dihydroxy-9,25-dimethyl units and it's enantiopure anti,anti-derivative is described. The synthesis was accomplished utilizing a linear approach in 7 steps and 3 % overall yield via a sequence of diastereoselective methylation of SuperQuat oxazolidinone auxiliary, cross metathesis and Yamaguchi macrolactonization of fully functionalized seco-acids. By a similar approach we gained access to several samroiyotmycin analogues and precursors. Antimalarial activity was tested on multi-resistant (K1) and sensitive (Nf54) P. falciparum strains providing insight into structure activity relationships. Both tosyl-oxazol unit as well as the syn-configuration of the two contiguous stereogenic centers turned out to be beneficial for antiplasmodial activity. For instance, syn,syn-tosyl-samroiyotmycin A showed 3.4 times higher activities than the "tosyl-free" natural product.