A convenient synthesis of lepidimoide from okra mucilage and its growth-promoting activity in hypocotyls

The total synthesis of the unsaturated disaccharide, lepidimoide 4-deoxy-beta-L-threo-hex-4-enopyranuronosyl-(1-->2)-L-rhamnopyranose sodium salt, has been carried out from D-glucose and L-rhamnose (Tetrahedron Lett. 1993, 34, 2653), but the process is very long and complicated. A method for more easily producing this compound and in large quantities is necessary for further research. We have succeeded in conveniently synthesizing lepidimoide from okra (Hibiscus esculentus L.) fruit mucilage. At the same time, the isomer (epi-lepidimoide) was obtained as a byproduct. The structure was determined as the 4-deoxy-beta-L-threo-hex-4-enopyranuronosyl-(1-->2)-6-deoxy-L-glucopyranose sodium salt by spectral analysis. We found that lepidimoide easily epimerized to epi-lepidimoide in alkaline media. Both lepidimoide and epi-lepidimoide exhibited the same high activity in the cockscomb hypocotyls elongation test.