Sphingolipids and Glycerolipids. IV. Syntheses and Ionophoretic Activities of Several Analogues of Soya-cerebroside II, a Calcium Ionophoretic Sphingoglycolipid Isolated from Soybean.

Abstract

For examination of the structure-activity relationship five analogues [(2'R)-2'-hydroxypalmitoyl (3), palmitoyl (4), (2'S)-2'-hydroxypalmitoyl (5), β-D-galactosyl (6), and 8, 9-dihydro (7) relevancies] of soya-cerebroside II (2), which is a calcium ionophoretic sphingoglycolipid isolated from soybean, have been synthesized by using our previously reported synthetic method for sphingoglycolipids. Examinations by using a W-08 (liquid-membrane type) apparatus and by means of the human erythrocyte membrane method, have shown that the (2'R)-2'-hydroxypalmitoyl analogue (3) exhibits higher ion-binding and ion-permeation activities for calcium ion than soya-cerebroside II (2), which contains 3 as the major component. It has also been found that the other analogues(5, 6, 7, 8) do not show those ionophoretic activities.An enantiomer (8) of the (2'R)-2'-hydroxypalmitoyl analogue (3) has been synthesized and its calcium ionophoretic activity examined. Compound 8 exhibits calcium ion-binding activity equal to that of 3, but 8 lacks the ability to support calcium ion-permeation through human erythrocyte membrane. Thus, human erythrocyte membrane precisely distinguishes the absolute configurations of 3 and 8 as regards calcium ionophoretic activity.