Synthesis method for high-purity cholesterol

A method for synthesizing cholesterol with plant-derived 21-hydroxy-20-methylpregn-4-en-3-one BA as raw material, wherein, the method uses BA as raw material to synthesize the cholesterol through oxidation, Wittig reaction, acetylation, reduction, hydroxyl protection, selective hydrogenation reduction, deprotection or hydrolysis, specifically comprising the following steps:

• step (a), in the first solvent, the BA shown in formula (1) undergoes oxidation reaction to obtain the compound of formula (2);
• step (b), in the second solvent, the compound of formula (2) undergoes Wittig reaction to obtain the compound of formula (3);
• step (c), in the third solvent, the compound of formula (3) undergoes acetylation reaction to obtain the compound of formula (4);
• step (d), in the fourth solvent, the compound of formula (4) undergoes reduction reaction to obtain the compound of formula (5);
• step (e), in the fifth solvent, the compound of formula (5) undergoes hydroxyl protection reaction to obtain the compound of formula (6);
• step (f), in the sixth solvent, the compound of formula (6) undergoes selective hydrogenation reduction reaction to obtain the compound of formula (7);
• step (g), in the seventh solvent, the compound of formula (7) undergoes deprotection or hydrolysis reaction to obtain cholesterol;
• wherein, the reaction process of the said method is as shown in route (A):
• Route (A)
• wherein, R is selected from ester group, silicon ether group.