Reaction Steps
To a solution of bisphosphonate 17 (2 g, 3.2 mmol) in 12 ml of anhydrous DMF under nitrogen is added at 0° C. via a cannula a solution of potassium thioacetate (1.1 g, 9.6 mmol) in 15 ml of anhydrous DMF. The mixture is stirred for 1.50 h at 0° C., quenched with water and extracted with EtOAc. The organic layer is dried over Na2SO4, filtered and evaporated. The residue is purified by flash chromatography (silica gel, MeOH:CH2Cl2 /0:100-2:98) to give bisthioacetate 18 (1.38 g, 70%) as a light yellow oil. IR (neat) 2980, 2932, 2230, 1692, 1600 cm-1 ; 1H NMR (CDCl3): δ 1.16 (6H, d, J=6.2 Hz), 1.18 (6H, d, J=6.2 Hz), 1.23 (12H, d, J=6.2 Hz), 2.26 (6H, s), 2.40 (1H, tt, J=24, 6.3 Hz), 3.07 (2H, td, J=16.5, 6.3 Hz), 4.00 (4H, s), 4.67 (4H, m), 6.95 (1H, s), 6.99 (2H, s); 13C NMR (CDCl3): δ 23.72, 23.75, 23.78, 23.84, 23.87, 23.90, 24.14, 30.25, 31.35 (t, J=4.8 Hz), 33.17, 40.59 (t, J=134 Hz), 70.98 (d, J=3 Hz), 71.01 (d, J=3 Hz), 71.15 (d, J=3 Hz), 71.28 (d, J=3 Hz), 127.24, 128.55, 137.62, 140.99 (t, J=7.6 Hz), 194.77; MS (APCI) m/z (relative intensity) 611 (MH+, 100), 569 (63), 527 (58), 485 (37), 453 (31)); MS (FAB) m/z (relative intensity) 611 (MH+, 100); HRMS calcd for C26H45O8P2S2 (MH+) 611.2031, found 611.2029.
