Convallatoxin synthesis

In their synthesis of convallatoxin, Reichstein and coworkers16 made some minor modifications in the Meystre-Miescher procedure. Because of the low solubility of strophanthidin (2) in benzene, the anhydrous aglycon was dissolved in a small volume of absolute p-dioxitne. Pure, dry silver carbonate was introduced and, under efficient stirring, a solution of the halide in benzene was added over a period of three hours, while distillation was maintained at a rate equal to that of the addition, thus keeping the volume of the solution in the flask at a constant (and small) volume. After addition of the halide was complete, a small volume of absolute benzene was added dropwise over a period of one hour, with distillation maintained as in the foregoing. By this procedure, the yield of tri-O-acetylcopvalla-toxin amounted to 44%. 

Following this work, Reichstein and coworkers15 effected the first partial synthesis of a naturally occurring cardenolide, convallatoxin. Convalla-toxin [3/3-0-(6-deoxy-a-n-mannopyranosyl) strophanthidin (9)] is considered to be the most potent of all the known, naturally occurring cardenolides, and is obtained from the blossoms of the lily-of-the-valley (Convallaria majalis). The coupling of strophanthidin (2) with 2,3,4-tri-0- acetyl-6-deoxy-a- L-mannosyl bromide was performed using silver car-... 

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