In 1862, it was discovered that cholesterol is converted into a new substance named coprostanol by the action of bacteria in the human digestive tract. Make use of the following information to deduce the structure of coprostanol. Identify the structures of unknowns J through M as well. 

(i) Coprostanol, upon treatment with Cr(VI) reagents, gives compound J, UV λ_max(ϵ) = 281(22) nm and IR = 1710 cm^-1. 

(ii) Exposure of cholesterol to H₂ over Pt results in compound K, a stereoisomer of coprostanol. Treatment of K with the Cr(VI) reagent furnishes compound L, which has a UV peak very similar to that of compound J, λ_max(ϵ) = 258(23) nm, and turns out to be a stereoisomer of J. 

(iii) Careful addition of Cr(VI) reagent to cholesterol produces M: UV lmax(e) 5 286(109) nm. Catalytic hydrogenation of M over Pt also gives L.