Dimethylformamide → 3-Aminorifamycin S

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Reaction Conditions

Reaction Steps

540 g of 3-bromo-rifamycin S are dissolved in 1500 ml of N,N-dimethyl formamide at 20° C. A steam of N2 is bubbled through the solution for 20', then 60 g of sodium nitrite are added portionwise allowing the temperature to rise to 39° C. while stirring under nitrogen atmosphere. The temperature is kept at 40° C. with a water bath for 30', then cooled at 20° C.; 10 g of urea are added and 70 ml of acetic acid are added dropwise. The steam of N2 is stopped and 130 g of zinc powder are added portionwise with vigorous stirring and cooling with an ice bath to keep the temperature below 60° C. The reaction mixture is stirred allowing the temperature to decrease to room temperature, and stirring is continued for 5 hours. The reaction mixture is filtered and the solution is diluted with 3000 ml of dichloromethane and washed with water several times. The dichloromethane solution is treated with manganese dioxide in order to oxidize 3-amino-rifamycin SV to 3-amino-rifamycin S. After filtration and evaporation to dryness, raw material such obtained is crystallized from 600 ml of 2-methoxy-ethanol to give 440 g of TLC pure 3-amino-rifamycin S in black crystals. U.V.; I.R. and PMR are identical to an authenic sample prepared according to W. Kump, H. Bickel, Helv. Chem. Acta, 56(7), 2348 (1973).

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