Several new compounds were isolated from the organic extract of the cyanobacterium Microcoleus lyngbyaceus, and their structures were determined by spectroscopic means. Polychlorinated acetamidoalkynes and alkanes were the major metabolites. 6-Acetamido-1,1,1-trichloroundecane, a positional isomer of the naturally occurring 5-acetamido-1,1,1-trichloroundecane, was synthesized in six steps from delta-decanolactone.