Polysulfides typically react readily with thiols, thus, reactions of endogenous cellular thiols with the polysulfide linkage in naturally-occuring pentathiepin cytotoxins are likely to be an important aspect of their biological chemistry. Here, it is reported that the reaction of thiols with the pentathiepin ring system initially produces a complex mixture of polysulfides that further decomposes in the presence of excess thiol to yield the corresponding 1, 2- ...