Studies will be carried out to synthesize depsipeptide lactone model compounds related to the depsipeptide portion of the quinoxaline antibiotics. The tridepsipeptide, N-carbobenzoxy-L-seryl-O-(N-t-bytyloxycarbonyl-L-valyl)-L-alanine 4-(methylthio)phyenyl ester has been prepared and will serve as a key intermediate in the preparation of related depsipeptide models. Following methods developed in the above model studies, efforts to effect the total synthesis of the quinoxaline antibiotic, triostin A, will be pursued. Studies also will be made to prepare dithiane amino acids, which comprise a structural moiety in the above antibiotics, via dehydroalanine and alpha-mercaptoalanine derivatives as synthetic precursors.