p-Toluenesulfonic acid → Pseudomonic acid C

Participants

Reaction Steps

Pseudomonic acid A (500 mgs) was dissolved in 2,2-dimethoxypropane (50 ml) and treated with p-toluene sulphonic acid (few crystals). After 1 hour the solution was diluted with ethyl acetate, washed with brine and dried (MgSO4). The solution was evaporated in vacuo and the residue redissolved in water-methanol (1:1, 20 ml) and potassium bicarbonate (100 mgs, 1 eq) added. The solvents were removed in vacuo and potassium selenocyanate (432 mgs, 3 eq) and iso-hexylalcoholwater (9:1, 15 ml) added and reaction refluxed for 4 days. After filtering, the reaction mixture was diluted with ethyl acetate (20 ml) and extracted with aqueous sodium bicarbonate (3×20 ml). The aqueous extracts were combined and acidified with acetic acid under a layer of ethylacetate (20 ml). After stirring for ca. 1 hour the organic layer was separated and aqueous layer further extracted with ethylacetate (3×20 ml). The combined extracts were washed with brine, dried (MgSO4) and evaporated to an oil. Chromatography of the oil on silica (5 g) gave pure pseudomonic acid C (215 mgs, 45%).

Provenance & Evidence