Convenient synthesis method of methylprotodioscin

A convenient synthesis method of methylprotodioscin belongs to the organic synthesis technical field. The method comprises the following steps: using the rich and cheap E/F full-ring-opening product of protodioscin, namely 26-choro-3beta,16beta-diacetoxy-22-one-5-cholestene as raw material to perform selective alcoholysis of C3-OAc and protection of C3-OH, then in THF/MeOH mixed solution, using the high selectivity of weak base K2CO3 to close E-ring to form C22-OH, then using methyl iodide to perform methylation to C22-OH, and finally performing a substitution reaction and deprotection of C3-OH. The synthesis of methylprotodioscin is realized in a concise and atom economy manner. The raw material and reagents used in the invention are cheap, the operation is simple, the reaction conditions are mild, the product is easy to separate and purify, the yield is high, especially by using the selective ring-opening reaction and the methylation reaction using the active methylating agent methyl iodide, the constructio