Microtropins A–I: 6′-O-(2″S,3″R)-2″-Ethyl-2″,3″-dihydroxybutyrates of aliphatic alcohol β-d-glucopyranosides from the branches of Microtropis japonica

Abstract

From the branches of Microtropis japonica (Celastraceae), nine aliphatic glucosides, named microtropins A-I, were isolated. The 6-position of glucose was esterified with (2S,3R)-2-ethyl-2,3-dihydroxybutyric acid. Microtropins A-D contained a rare natured product nitrile functional group in their aglycones. The absolute structures of the (2S,3R)-2-ethyl-2,3-dihydroxybutyric acid moiety and aglycone of microtropin A were determined by an X-ray crystallographic method.