Sugar-derivatives of potassium lespedezate, artificial leaf-opening substances of Lespedeza cuneata G. Don, designed for the bioorganic studies of nyctinasty

Potassium lespedezate (1) is the leaf-opening substance of a nyctinastic plant, Lespedeza cuneata G. Don. We synthesized two sugar-derivatives of 1, potassium galactolespedezate (2) and mannoisolespedezate (3). Both 2 and 3 were quite effective for the leaf-opening of L. cuneata, at 8 x 10^-7 M, as strong as 1. However, 1 kept the leaf open only for a few days; on the other band, 2 and 3 kept the leaf open after a week at that concentration. Thus, it is assumed that 2 and 3 could not be hydrolyzed by α-glucosidase in the plant body, and are therefore potentially useful molecular probes for the studies of the control of the nyctinastic leaf-movement by a biological clock.