Fig. 5
First total synthesis of rac-xestospongiene. Reagents and conditions: i. ethynyl-magnesium bromide (1.7 equiv.), THF, rt, 12.5 h; ii. NaH (1.0 equiv.), THF, 0 °C, 0.5 h, then rt, 0.5 h; then MeI (1.2 equiv.), 0 °C, 2 min, then rt, 5 h; then HCl (aq., 3.0 M), 0 °C, then rt, 1.5 h; iii. Fe(NO3)3∙9H2O (8 mol%), TEMPO (8 mol%), NaCl (8 mol%), O2 balloon, DCM, 25 °C, 12.5 h; iv. CBr4 (1.5 equiv.), PPh3 (3.0 equiv.), DCM, 0 °C, 0.5 h, then 0 °C ~ rt, 1 h; v. rac-3a (1.5 equiv.), methyl 4-oxobutanoate 2k (1.5 equiv.), CuBr2 (20 mol%), dioxane, 130 °C, 17 h; vi. LiOH∙H2O (1.5 equiv.), EtOH/H2O = 1:1, 90 °C, 1.5 h; vii. AuCl(LB-Phos) (10 mol%), AgOTs (10 mol%), CHCl3, -30 °C, 24 h
