To a solution of N-(2-amino-6-methylpyridin-3-ylmethyl)-N-{2-[2-[(2-amino-6-methyl-pyridin-3-ylmethyl)formylamino]-1-(2-hydroxyethyl)-propenyldisulfanyl]-4-hydroxy-1-methylbut-1-enyl}formamide (250 mg, 0.45 mmol) and propyl disulfide (0.21 mL, 1.34 mmol) in methanol (3 ml) was added 1 molar aqueous sodium hydroxide (0.089 mL, 0.089 mmol). The resulting solution was stirred at 35-45° C. for 18 hr. The solution was diluted with water (10 mL) and chloroform (10 mL), but the product remained as a milky insoluble layer. Addition of ethyl acetate (10 mL) and methanol (2 mL) resulted in the formation of two clear layers. The product was contained in the lower layer. This layer was washed with brine (10 mL) dried over sodium sulfate, and evaporated. The residual oil was dissolved in chloroform (1 mL) and chromatographed on silica gel (Waters Sep-Pak 5 g column, using 97.5/2.5 chloroform/methanol as eluent, Fraction size 9 mL). Fractions 4-9 were pooled and evaporated to give 130 mg (41%) of the title compound as nearly colorless oil. MS (LCMS): 356.0 (M+H)+. 1H NMR (CDCl3) δ 0.95 (t, 3H), 1.55 (m, 3H), 1.97 (s, 3H), 2.35 (s, 3H), 2.42 (t, 2H), 2.84 (t, 2H) 3.76 (t, 2H), 5.36 (br. s, 1H), 6.35 (d, 1H), 7.02 (d, 1H), 7.96 (s, 1H).
