Compounds 1–5 (1–2 mg) were dissolved in 1 N HCl (1 mL) and heated at 80 °C under condition of reflux for 3 h. The solution was neutralized with Ag2CO3 and evaporated under N2 gas. The residue was dissolved in H2O and partitioned with CH2Cl2. The aqueous layer was concentrated and the H2O was thoroughly removed using N2 gas. The residue was dissolved in pyridine (200 μL), and then l-cysteine methyl ester hydrochloride in pyridine (0.06 M, 200 μL) was added to the solution. The reaction mixture was incubated at 60 °C for 2 h, and trimethylsilylimidazole (200 μL) was added followed by heating at 60 °C for 1.5 h. After drying the mixture, the residue was partitioned with n-hexane and H2O (0.1 mL, each) and the n-hexane layer was subjected to GC under the following conditions; column BPX50 (0.25 mm × 30 m); carrier gas He; column temperature 210 °C; injector temperature 270 °C; detector temperature 300 °C. Under the above conditions, authentic d-glucose, l-rhamnose gave GC peaks at tR 11.87 and 9.21 min, respectively, and the tR of the sugars of the isolates obtained by acid hydrolysis gave similar results as those of standard sugars.