NOVELTY - Preparing difluprednate comprises e.g. adding (2-((10S,11S,13S,17R)-11,17-dihydroxy-10,13-dimethyl-3-oxo-2,4,5,6,7,8,9,11,12,14,15,16-dodecahydro-1H-cyclopenta(a)phenanthren-17-yl)-2-oxo-ethyl) acetate (II), performing dehydrating reaction to generate a (2-((10S,13S,17R)-17-hydroxy-10,13-dimethyl-3-oxo-2,4,5,6,7,8,12,14,15,16-decahydro-1H-cyclopenta(a)phenanthren-17-yl)-2-oxo-ethyl) acetate (III), mixing (III) with butyric acid to obtain ((10S,13S,17R)-17-(2-acetoxyacetyl)-10,13-dimethyl-3-oxo-2,4,5,6,7,8,12,14,15,16-decahydro-1H-cyclopenta(a)phenanthren-17-yl) butanoate.    USE - The method is useful for preparing difluprednate (claimed).    ADVANTAGE - The method economically prepares the difluprednate with high yield and low toxicity in an eco-friendly manner.    DETAILED DESCRIPTION - Preparing difluprednate comprises (a) adding (2-((10S,11S,13S,17R)-11,17-dihydroxy-10,13-dimethyl-3-oxo-2,4,5,6,7,8,9,11,12,14,15,16-dodecahydro-1H-cyclopenta(a)phenanthren-17-yl)-2-oxo-ethyl) acetate (II), performing dehydrating reaction to generate a (2-((10S,13S,17R)-17-hydroxy-10,13-dimethyl-3-oxo-2,4,5,6,7,8,12,14,15,16-decahydro-1H-cyclopenta(a)phenanthren-17-yl)-2-oxo-ethyl) acetate (III), (b) mixing (III) with butyric acid using esterification reaction to obtain a ((10S,13S,17R)-17-(2-acetoxyacetyl)-10,13-dimethyl-3-oxo-2,4,5,6,7,8,12,14,15,16-decahydro-1H-cyclopenta(a)phenanthren-17-yl) butanoate (IV), (c) mixing (IV) with alcohol for esterification reagent to obtain a ((3S,5S,10S,13S,17R)-3-acetoxy-17-(2-acetoxyacetyl)-10,13-dimethyl-1,2,3,4,5,6,7,8,12,14,15,16-dodecahydrocyclopenta(a)phenanthren-17-yl) butanoate (V), (d) mixing (V) with a fluorinating reagent to obtain a butyric acid (6R,10R,13S,17R)-17-(2-acetoxy-acetyl)-6-fluoro-10,13-dimethyl-3-oxo-2,3,6,7,8,10,12,13,14,15,16,17-dodecahydro-1H-cyclopenta(a) phenanthren-17-yl ester (VI), (e) adding (VI) by turning reaction to obtain a butyric acid (6S,10R,13S,17R)-17-(2-acetoxy-acetyl)-6-fluoro-10,13-dimethyl-3-oxo-2,3,6,7,8,10,12,13,14,15,16,17-dodecahydro-1H-cyclopenta(a)phenanthren-17-yl ester (VII), (f) mixing (VII) with N-bromosuccinimide and water to obtain a butyric acid (6S,9R,10S,11S,13S,17R)-17-(2-acetoxy-acetyl)-6,9-difluoro-11-hydroxy-10,13-dimethyl-3-oxo-2 ,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta(a)phenanthren-17-yl ester (VIII), (g) mixing (VIII) with alkaline using epoxidation to obtain a butyric acid (6S,10R,13S,17R)-17-(2-acetoxy-acetyl)-6-fluoro-10,13-dimethyl-3-oxo-2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta(a)phenanthren-17-yl ester (IX), (h) mixing (IX) with fluorinating agent to obtain a butyric acid (6S,9R,10S,11S,13S,17R)-17-(2-acetoxy-acetyl)-6,9-difluoro-11-hydroxy-10,13-dimethyl-3-oxo-2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta(a)phenanthren-17-yl ester (X), and (i) adding (X) by an oxidative dehydrogenation.    An INDEPENDENT CLAIM is also included for synthesizing difluprednate key intermediate compound of formula IV.