Total synthesis of somamide A, an Ahp (3-amino-6-hydroxy-2-piperidone)-containing cyclic depsipeptide

The first total synthesis of somamide A (1), an Ahp (3-amino-6-hydroxy-2-piperidone)-containing cyclic depsipeptide, from the marine cyanobacterium Lyngbya majuscula is described. The efficient and stereospecific dehydration of the N-acyl threonine ester using Martinʹs sulfurane provided the (Z)-2-amino-2-butenoic acid residue. The macrolactamization using FDPP(Ph2P(O)OC6F5), the final installation of the Ahp moiety by oxidation with 1-hydroxy-1,2-benziodoxol-3(1H)-one 1-oxide, and cyclization of the norvaline derivative to the cyclic hemiaminal afforded somamide A (1).