Reaction Steps
A solution of S-trans, trans-farnesyl-L-cysteine (500 mg, 1.54 mmol) in THF and a first portion of K2CO3 (3 mmol) was cooled to 5° C. with vigorous stirring. To this stirred solution was added maleic anhydride (302 mg, 3.07 mmol) portionwise while maintaining the pH at 9.0-10.0 with another portion of K2CO3 (3 mmol). The mixture was stirred at room temperature for 3 h, HPLC analysis showed completion of the reaction. The pH of the reaction mixture then adjusted to 2.0 by the addition of 2 N HCl solution. The acidic solution was extracted three times with 15 mL of ethyl acetate. The combined organic extract was washed with water, brine and dried over Na2SO4 and then concentrated to afford crude Compound A, which was further purified by preparative HPLC (552 mg, 85%) to yield Compound A. 1H-NMR (500 MHz, CD3OD): δ 1.50(bs, 6H), 1.57(s, 3H), 1.59 (s, 3H), 1.85-2.10 (m, 8H), 2.68 (dd, J=6.5, 14.5, 1H), 2.95 (dd, J=4.5, 14.0 Hz, 1H), 3.07 (dd, J=7.0, 13.0 Hz, 1H), 3.17 (dd, J=8.5, 13.5 Hz, 1H), 4.59 (dd, J=4.5, 8.5), 4.97-5.02 (m, 2H), 5.12 (t, J=7.5, 1H), 6.21 (d, J=13.0 Hz, 1H), 6.47 (d, J=13.0 Hz, 1H). 13C-NMR (125 MHz, CDCl3): δ 16.2, 16.3, 17.8, 25.3, 26.0, 27.4, 27.8, 30.3, 33.3, 40.8, 40.9, 54.0, 121.5, 125.1, 125.5, 132.1, 133.3, 134.4, 136.3, 140.7, 167.7, 168.0, 172.9; ES-MS: mass calcd for Chemical Formula: C22H33NO5S 423.6. Found (M+Na) m/z 446.
