Reaction Steps
Me3SnOH (496 mg, 2.74 mmol) was added to a 0.020 M solution of methyl ester 23 (175 mg, 0.343 mmol) in dichloroethane (17.0 mL). The reaction mixture was heated to 60° C. for 20 h and then concentrated. Column chromatography (100% CH2Cl2 to elute tin containing materials followed by 80:20:1 CH2Cl2:MeOH:NH4OH to elute the product) afforded 150 mg (88%) of 24 as an amorphous solid. The 1H NMR corresponds to a 6:1 mixture of rotamers, with the major isomer reported. [α]D23=−17.4 (c=1.0, MeOH). IR: 1276, 1368, 1471, 1616, 2874, 2961 cm−1. 1H NMR (500 MHz, d6-DMSO): δ 0.70 (m, 3H), 0.75-0.82 (m, 3H), 0.83-0.90 (m, 6H), 1.04-1.16 (m 1H), 1.17-1.28 (m, 2H), 1.37-1.55 (m, 3H), 1.56-1.72 (m, 3H), 1.73-1.91 (m, 3H), 2.00-2.24 (m, 2H), 2.22 (s, 3H), 2.84 (br s, 1H), 2.94-3.00 (m, 1H), 3.04 (s, 3H), 4.16-4.60 (br s, 1H), 4.49 (d, 1H, J=10.5), 4.56 (app t, 1H, J=9.0), 5.93-6.40 (br s, 1H), 8.05 (s, 1H), 8.25 (s, 1H). 13C NMR (125 MHz, d6-DMSO): δ 10.0, 14.7, 19.1, 19.5, 19.6, 21.8, 23.58, 23.62, 28.75, 28.8, 35.2, 36.7, 42.6, 52.3, 54.1, 67.1, 67.5, 126.7, 147.8, 162.2, 170.7, 172.0, 177.6. HRMS (FAB) calcd for C24H41N4O5S (M+H): 497.2798. Found: 497.2793.
