Potassium lespedezate (1) is the leaf-opening substance of a nyctinastic plant, Lespedeza cuneata G. Don. We have synthesized two sugar-derivatives of 1, potassium galactolespedezate (4) and mannolespedezate (6). Both 4 and 6 were quite effective for the leaf-opening of Cassia. mimosoides at 8 x 10-7 M, as strong as 1. However, 1 kept the leaf open only for a few days; on the other hand, 4 and 6 kept the leaf open after a week at that concentration. Additionally, remarkable difference was observed in the rate of enzymatic hydrolysis of natural and artificial leaf-opening sustance by using commercially available β-glucosidase. Therefore, 4 and 6 would not be hydrolized in the plant body, and are potentially useful molecular probes for the studies of the control of the nyctinastic leaf-movement by a biological clock.
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