Patent ID: 7432088

Claim:
A process for preparing purified ansamitocins comprising the steps of: 1) culturing an ansamitocin-producing microorganism in a liquid culture medium; 2) solid phase extraction of ansamitocins from the culture medium onto a hydrophobic resin; 3) isocratic or gradient elution of ansamitocins from the resin using an organic solvent or an organic solvent combined with water; 4) concentrating the extracted ansamitocins; and 5) optionally purifying the ansamitocins by any one of a), b), c) and d): a) adsorption chromatography over silica gel or alumina, b) crystallization, c) adsorption chromatography over silica gel or alumina followed by crystallization, and d) crystallization followed by adsorption chromatography over silica gel or alumina; and wherein said ansamitocin has the following structure: wherein R is H, COCH 3 , COCH 2 CH 3 , COCH(CH 3 ) 2 , COCH 2 CH 2 CH 3 , COCH 2 CH(CH 3 ) 2 or COCH 2 CH 2 CH 2 CH 3 .