The invention discloses a compound represented by a general formula 1 and a preparation method thereof. In the structural formula, X=Y=O, or X=S, Y=O, or X=Y=S; and R represents phenyl, benzyl or isopropyl. The invention also discloses a method for synthesizing a compound represented by a general formula 3, and a method for synthesizing chiral dorzolamide hydrochloride, which are formed by carrying out one step reaction and multi-step reaction on the compound represented by the general formula 1. The compound synthesizes the chiral dorzolamide hydrochloride used for treating glaucoma by adopting a classical chiral prosthetic group induction method, and has the advantages of good yield, no racemization and high optical purity.