Silica ether

To a solution of phenylthio disaccharide 3 (56 mg, 0.11 mmol) in CHjC (2 mL) at —15°C was added DAST (21 pL, 0.16 mmol), followed by Af-bromosuccinimide (25 mg, 0.14 mmol). After stirring at — 15°C for 15 min, the reaction mixture was poured onto saturated aqueous NaHC03 solution (5 mL) and extracted with ether (3 x 10 mL). The organic extracts were combined, washed with brine (5 mL), and dried (MgS04). Evaporation of the solvent followed by flash chromatography (silica, ether-petroleum ether) gave the disaccharide fluoride 4 (40 mg, 85%) with an anomeric ratio of 5 1 (oc/p). 

To a suspension of AgC104 (95 mg, 0.46 mmol), SnCl2 (87 mg, 0.46 mmol), and crushed 4-A molecular sieves (200 mg, dried) in ether (3.5 mL) at —15°C was added alcohol 11 (224 mg, 0.25 mmol) in ether (3.5 mL). After 2 min, tetrasaccharide fluoride 13 (454 mg, 0.25 mmol) in ether (3.5 mL) was added in one portion, and the reaction mixture was allowed to stir at - 15°C for 2 h and at room temperature for 10 h. The reaction mixture was diluted with ether (50 mL) and filtered through Celite. The filtrate was washed with saturated aqueous NaHCOj solution (2 mL) and brine (2 mL), dried (MgS04), and evaporated to give a yellow syrup. Purification by flash chromatography (silica, ether-petroleum ether) afforded hexasaccharide 14 (442 mg, 66%) [a]D +66.50° (c 1.9, CH2C12). 

The mixture was stirred and allowed to warm to room temperature. After stirring I h, the reaction mixture was diluted with ether (10 mL) and poured onto saturated aqueous NaHCOj solution (2 mL). The organic layer was washed with brine, dried (MgS04), concentrated, and purified by flash column chromatography (silica, ether-petroleum ether) to afford disaccharide fluoride 55 (21 mg, 83%) [ ] -23.94° (c 1.42, CHC13). 

Ointment with zinc oxide TLC Shake with ether, Silica Ether-EtOH-AcOH 350 nm JP, p. 1306 identification [7]... 

Bulk TLC Dissolve in methanol-chloroform (1 1) Silica Ether (water sat.) DMAB BP, p. 282 (4]... 

Santonin crystals (250 mg) were crushed between two Pyrex plates and photo-lyzed with a Hanovia 400 W lamp for 3 days. The bright yellow powder was dissolved in 50 mL of ethyl acetate. The reaction mixture was analyzed using GC, IR and NMR. The solvent was removed and the residue was chromatographed over silica (ether hexane = 30 70). 

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