Part I deals with the structure determination of five organic compounds by X-ray diffraction methods: the diacetate of the sesquiterpene voleneol, which in spite of having five chiral centers, was isolated from a plant as the racemate; two 1,4-dithiin 1,1,4,4-tetroxides, one an herbicide and the other a microbiocide; bouvardin, a bicyclic hexapeptide with anti-tumor activity; and a tripeptide that is an intermediate in a synthesis of the anti-tumor agent deoxybouvardin and which contains a novel hydrogen bond. Part II details efforts to synthesize deoxybouvardin. Compounds synthesized include the corresponding monocyclic hexapeptide (which shows no anti-tumor activity) and various precursors to the 14-membered ring of deoxybouvardin.