Step 4:Preparation of compound 8
To a solution of 7 (200mg, 0.465mmol, 1.0 eq) in deionized water (3ml,
c=0.15) was added AgCl (133mg, 0.93mmol, 2.0 eq). After addition, the
reaction mixture was stirred at room temperature overnight. The
suspension was then filtered and the filtrate was lyophilized to give
compound 8 (141mg, yield=89.8%) as a solid. HPLC purity: at 220nm;
Mass: M+1=339.4. 1H NMR (300 MHz, D2O): δ 7.117 (m, 3H), 4.056 (dd,
J=8.1 Hz, 1H), 3.712~3.808 (m, 1H), 3.656 (m, J=13.2 Hz,
2H), 3.510~3.582 (m, 1H), 3.344 (m, 2H), 2.117 (s, 6H),
1.984~2.070 (m, 2H), 1.818 (m, 4H), 1.660 (m, 1H), 1.455
(m, 1H), 1.278 (t, J=7.2 Hz, 3H), 1.107 (t, 3H) ppm.