A process of making entecavir comprising converting a compound of formula (M5) to entecavir, wherein the two PGs on the formula (M5) are taken together to form an optionally substituted six- or seven-member cyclic ring.本發明係關於一種製備恩替卡韋(entecavir)之方法,其包含將式(M5)化合物轉化成恩替卡韋,其中該式(M5)上之兩個PG一起形成視情況經取代之6員或7員環狀環。