alfalfa-root saponin (compound F) was isolated and its chemical structure determined as 3β-[ O -α- d -glucopyranosyl-(1→4)-β- d -glucopyranosyl]-2β-hydroxy-Δ 12 -oleanene-23,28-dioic acid (3β-medicagenic acid β-maltoside). It was synthesized via a modified Koenigs-Knorr reaction employing light-sensitive esters as protective groups for the aglycon. The saponin has antimycotic activity against some