Реакция #990368

Уравнение реакции

potassium selenocyanate

p-toluene sulphonic acid

Pseudomonic acid A

potassium bicarbonate

→

pseudomonic acid C

Выход 45.0%

Растворители

ethyl acetate

2,2-dimethoxypropane

Условия реакции

Обработка

1. 1
   Промывкаwashed with brine
2. 2
   Сушкаdried (MgSO4)
3. 3
   ДругоеThe solution was evaporated in vacuo
4. 4
   workup.DISSOLUTIONthe residue redissolved in water-methanol (1:1, 20 ml)
5. 5
   workup.ADDITIONadded
6. 6
   Другоеreaction
7. 7
   Температураrefluxed for 4 days
8. 8
   ФильтрацияAfter filtering
9. 9
   workup.ADDITIONthe reaction mixture was diluted with ethyl acetate (20 ml)
10. 10
    Экстракцияextracted with aqueous sodium bicarbonate (3×20 ml)
11. 11
    Другоеwas separated
12. 12
    Экстракцияaqueous layer further extracted with ethylacetate (3×20 ml)
13. 13
    ПромывкаThe combined extracts were washed with brine
14. 14
    Сушкаdried (MgSO4)
15. 15
    Другоеevaporated to an oil

Методика

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%).

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