Thermodynamically stable crystal form of 4'-deoxy-4'(epi)-methylamino avermectin b1a/b1b benzoic acid salt and processes for its preparation

摘要

This invention is concerned with the most stable of four crystalline forms of the benzoic acid salt of 4"-deoxy-4"-epi-methyl-amino avermectin B1a/B1b a known agricultural insecticide, and processes for preparing it. The four crystalline forms that have been identified are designated as forms A, B, C and D, three of which are hydrates (B, C and D). The most thermodynamically stable crystalline form is the hemi-hydrate B. Knowing the most stable crystalline form and devising processes for producing the product in that form is extremely important that it provides bulk material with crystal homogeneity that is not going to transform to another crystal habit on storage.