To a 1 L three neck flask fitted with a thermometer, mechanical stirrer, addition funnel, under argon was added the chlorosulfonamide 7 (35 g, 0.082 mol) dissolved in THF (500 mL). The reaction mixture was cooled to −62° C. LDA (Lithium diisopropylamide, 2.0 M in heptanes/THF/ethylbenzene, 193 mL, 0.385 mol) was added drop wise over 90 min. The reaction mixture warmed to −30° C. The cooling bath was turned off and 1M HCl (1 L) was added slowly initially, then the solution was transferred to a reparatory funnel where the remaining HCl was added to pH 2. The layers were separated and the aqueous layer was extracted with ethyl acetate (400 mL). The organic layers were combined and washed with sat. NaHCO3 (250 mL) and brine (250 mL). The organic layer was dried over MgSO4 (10 g) filtered and concentrated under reduced pressure to 37.2 g of an orange oil. The oil was flash chromatographed over flash silica gel (400 g) with anhydrous Na2SO4 (100 g) on top of the column packed with hexanes. Fractions of 500 mL were collected. Fractions 1-17 were eluted with pure hexanes up to 12% ethyl acetate in hexanes, 18-26 with 20% ethyl acetate in hexanes, 27-30 with 50% ethyl acetate in hexanes. Fractions were monitored by TLC (EtOAc:hexanes; 1:1) and HPLC. Fractions 21-29 were combined and concentrated under reduced pressure and further dried submersed in a warm water bath at 50° C. under high vacuum over night to give 18.8 g (59%) of the final product 8 as a viscous honey colored oil. HPLC analysis showed a purity of 95%. 1H NMR (300 MHz, CDCl3) δ 7.3-7.7 (m, 10H), 4.4-4.6 (br s, 1H), 3.6-3.9 (m, 3H), 3.2 (m, 2H), 2.1-2.6 (m, 2H), 1.1 (s, 9H). This batch was sent as lot #07-OC-FP-019.
