Nostocyclophanes A-D are the cytotoxins associated with the blue-green alga Nostoc linckia (Roth) Bomet ex Bornet & Flahault (UTEX B1932). The gross structures of these [7,7]paracyclophanes have been elucidated by mass and NMR spectral analyses and the relative and absolute stereochemistry of nostmyclophe D determhed by X-ray crystallography. Since the CD spectra of the four compounds are essentially identical, noetocyclophanea A-D are proposed to have the same stereochemistry. The sugar unit in noetocyclophanes A and B has been shown to be D-glucose by semisynthesis of nostocyclophane B 9-O-(2,3,4,6-tetra-O-acetyl)-β-D-glucopyranoside from nostocyclophanes B and D. Rates of the hydrolysis of m-(2-imidazolylazo)phenyl p-toluenesulfonate (1) were measured in the presence of Cu(II) ion. Saturation behavior was observed for the dependence on [Cu(II)] of the absorbance (Abs) of 1 or that of the pseudo-first-order rate constant (ko). The formation constant measured from the dependence on [Cu(II)] of ko was much smaller than that of Abs. The binding constant reflected in the Abs data indicates the formation of a 1:1-type complex. The binding constant estimated with the ko values may be related to the formation of a 2:1-type complex. This possibility, however, is excluded on the basis of the dependence of the binding constanta on pH and the dependence of Abs on [Cu(II)]. Instead, the saturation kinetic behavior agrees with the shift of the rate-determining step between the formation and the breakdown proce%see of an intermediate upon increase in [Cu(II)]. On the basis of the kinetic data, it is shown that the 1:1-type complex is hydrated to form an addition intermediate, which is subsequently converted into the hydrolysis producta, and that hydroxocopper(II) ion participates as a general-base catalyst in the rate-controlling proton-transfer process.