[2aR-[2aalpha,4beta,4abeta,6beta,9alpha(2R,3R),10beta,11beta,12alpha,12aalpha,12balpha]]-12b-Acetoxy-12-benzoyloxy-9-[3-(tert-butoxycarbonylamino)-4,4-difluoro-2-hydroxybutyryloxy]-6-(3,3-dimethylbutyryloxy)-4,11-dihydroxy-4a,8,13,13-tetramethyl-2a,3,4,4a