Patent ID: 8293929

Claim:
A process of producing a compound of comprising purifying a mixture of wherein R 8 is a protecting group and R 9 is C 1 -C 5 alkyl, and purifying includes selectively crystallizing the mixture with an organic solvent, or dynamically crystallizing the mixture wherein: selective crystallization comprises combining the mixture and an organic solvent at or above room temperature and warming the combination with stirring to dissolve the mixture and then cooling the combination; and wherein: dynamically recrystallizing the mixture comprises contacting the mixture with a Lewis acid and a solvent optionally including a protic acid; wherein: the organic solvent is selected from toluene, dioxane, THF, or mixtures thereof; the lewis acid is selected from BF 3 -etherates, metal halides, alkoxides, or mixed halide/alkoxides; the mixed halide alkoxides are selected from Al(Oalkyl) 2 Cl or Al(Oalkyl)Cl 2 ); the alkyl group of the alkyl or alkoxide is a straight or branched chain having one to twelve carbon atoms; the metal is aluminum, titanium, zirconium, magnesium, copper, zinc, iron, tin, boron, ytterbium, lanthanum, or samarium; and the protic acid is selected from HCl, HBr, triflic acid, sulfuric acid, phosphoric acid, or combinations thereof.