Preparation method of pleuromutilin antibiotic

The invention discloses a synthesis method of a pleuromutilin antibiotic, and the synthesis method comprises the following steps: (1) reacting p-toluenesulfonyl chloride with pleuromutilin to obtain p-toluene sulfonyl pleuromutilin; (2) reacting tropanol with hydrogen bromide to obtain bromo-tropane; (3) reacting Na2S2 with bromo-tropane to obtain dithio-tropane; (4) heating and refluxing dithio-tropane and a strong base for disulfide bond cleavage to obtain a product namely mercapto-tropane; and (5) reacting p-toluene sulfonyl pleuromutilin with mercapto-tropane to obtain the pleuromutilin antibiotic (retapamulin) shown in formula (I), which is shown in the specification. The preparation method of retapamulin disclosed by the invention has the advantages of inexpensive raw materials, lowcorrosion of reaction liquid to equipment during production process, low production cost, and great economic and social benefits, and meets the requirements of green ecology and sustainable development, wherein the yield of retapamulin is high and the purity of the prepared retapamulin is high.