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A solution of 19.0 g (0.100 mol) of 77 in 300 ml of dry chloroform was refluxed under vigorous stirring with 40 g of P2O5 for 24 h. The mixture was filtered after cooling. The filtrate was evaporated in vacuo leaving a red oil. The precipitate was dissolved in water at 0°-5° C. and the aqueous solution made basic with sodium carbonate. Extraction with 3×200 ml of dichloromethane, drying of the combined organic phases over magnesium sulphate, and removal of the solvent in vacuo gave a red oil which was combined with the above mentioned oil obtained from the chloroform phase. The oil was applied to a silica gel column (eluent; methanol/ether=1/19) giving a colorless oil, 78. Yield: 5.9 g (0.034 mol, 34%).

1. filtrationThe mixture was filtered
2. temperatureafter cooling
3. customThe filtrate was evaporated in vacuo
4. customleaving a red oil
5. extractionExtraction with 3×200 ml of dichloromethane
6. dry with materialdrying of the combined organic phases over magnesium sulphate, and removal of the solvent in vacuo
7. customgave a red oil which
8. customgiving a colorless oil, 78