TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Processes: Acylation reaction is performed by adding iodine catalyst to D-maltose acetic anhydride solution at room temperature, stirring to react until solution turns into reddish brown, stopping reaction, pouring reaction liquid in sodium thiosulfate ice water solution, edge-pouring, edge-stirring, separating out flocculent precipitate during stirring process, adding organic solvent to dissolve flocculent precipitate, and post-processing to obtain octa-O-acetyl- alpha -D-maltose. Post-processing to obtain octa-O-acetyl- alpha -D-maltose is performed by extracting using organic solvent, collecting oil layer, and vacuum-distilling to remove solvent to obtain oily product. Bromination reaction is performed by dissolving octa-O-acetyl- alpha -D-maltose in methane chloride, adding hydrogen bromide acetic acid solution under ice bath condition, stirring reaction for 20-30 minutes, stirring reaction for 2-4 hours at room temperature, pouring reaction liquid in beaker filled with ice water and methane chloride, edge-pouring, edge-stirring, and post-processing to obtain hepta-O-acetyl- alpha -D-bromo-maltose. Post-processing to obtain hepta-O-acetyl- alpha -D-bromo-maltose is performed by extracting reaction mixture using separatory funnel, washing aqueous layer using organic solvent, collecting oil layer, washing using ice water, regulating pH at 7-8, separating oil layer, washing using saturated salt water, drying, and vacuum-distilling to remove organic solvent to obtain pale yellow solid. Reaction after adding thiourea is performed by dissolving hepta-O-acetyl- alpha -D-bromo-maltose in acetone, adding thiourea while stirring in which molar ratio thiourea:hepta-O-acetyl- alpha -D-bromo-maltose is 1:1-3:1, raising temperature to 50-80 degrees C, refluxing for 4-8 hours, and vacuum-distilling to remove acetone in reaction mixture. Hydrolysis reaction is performed by adding methane chloride in hepta-O-acetyl- beta -D-maltose isothiourea hydrobromide aqueous solution in which volume ratio aqueous solution:methane chloride is 1:1-1:5, adding sodium pyrosulfite while stirring to obtain reaction mixture in which molar ratio sodium pyrosulfite:hepta-O-acetyl- beta -D-maltose isothiourea hydrobromide 1:1-3:1, heating to 50 degrees C, refluxing for 3-8 hours at 50 degrees C, and post-processing to obtain hepta-O-acetyl-1-mercapto- beta -D-maltose. Post-processing to obtain hepta-O-acetyl-1-mercapto- beta -D-maltose is performed by extracting reaction mixture using separatory funnel, washing aqueous layer using organic solvent, collecting oil layer, washing using saturated salt water, drying oil layer over anhydrous sodium sulfate, vacuum-distilling to remove organic solvent to obtain white solid, re-crystallizing obtained white solid using isopropyl alcohol, and drying. Preferred Compositions: Hydrogen bromide acetic acid solution concentration is 37-45 wt.%. Volume ratio water:organic solvent in water and organic solvent mixture is 1:1-3:1.