Method for synthesizing cholesterol by using pregnenolone as raw material

The invention provides a method for synthesizing cholesterol by using pregnenolone as a raw material. The method comprises the following steps: 1) adding potassium acetate into methyl alcohol, and performing a reaction on sulfonate to obtain 6-methoxyl-3,5-cyclo-5alpha-pregn-20-one; 2) performing a reaction on triphenylphosphine and 1-chloro-4-methylpentane in an aprotic solvent to obtain a 4-methylbutyltriphenyl phosphonium chloride solution; 3) adding potassium tert-butoxide into the 4-methylbutyltriphenyl phosphonium chloride solution, and performing a wittig reaction; 4) under the catalysis of a rhodium catalyst, performing an asymmetric hydrogenation reaction to obtain 6-methoxyl-3,5-cyclo-5alpha-cholestane; 5) performing a catalytic hydrolysis deprotection reaction by using sulfuric acid to obtain the cholesterol. The method provided by the invention has the advantages that six-step reactions in the conventional method are simplified into four-step reactions, and a ring-opening reaction in which a great number of hydrochloric acid and a large number of zinc powder are consumed in a route of using saponin as an initial raw material. The synthesizing method is simple in process, the consumption of the raw material and auxiliary materials is low, and the mole yield is high; the method is economical and environmentally friendly, and facilitates industrial implementation.