Experiments 15 Flash column chromatography

With the requisite aldehyde 26 in hand, the stage was now set for the key intramolecular aldol cyclization. Thus, treatment of 26 with 4 equivalents of DBU in refluxing benzene gave the cyclized product in a ratio of 14 1, and the major product 27 was isolated in 60% yield by flash column chromatography. The major product in this key reaction was cw-octahydroquinolinone as expected. The stereochemistry of the major product was determined by the NOE experiment shown in Scheme 13. 

Experiment 14. Purification of proteins on DEAE-cellulose Experiment 15. Separation of a mixture of analgesics by flash column chromatography... 

Flash chromatography (FC) is a simple, low cost and rapid column chromatographic technique used principally for the separation and purification of mixtures of organic compounds (Chapter 9, Experiment 15). The technique, first described by Still [1] uses a smaller and narrower range particle size of packing than conventional preparative column chromatography and as such has to be carried out with a slightly increased over-pressure in order to achieve adequate flow-rates. 

You will normally have had experience of flash chromatography before ittempting mplc, and the two are really quite similar except that the relationship between tic polarity and column solvent is slightly different. 

Typical procedure. Methyl (1aS,8R,8aS,8bR)-1,1a,2,8,8a,8b-hexahydro-7-benzYloxY-8-(benzYloxYcarbonyl)oxymethyl-l-tert-butyloxycarbonyl-8-formylazirino[2, 3 3,4] pyrrolo-[1,2a]indole-5-carboxylate 917 [659] CDI (150 mg, 0.925 mmol) was added to a solution of alcohol 916 (385 mg, 0.779 mmol) in acetonitrile (12 mL), and the reaction mixture was stirred for 3.5 h. Benzyl alcohol (600 gL, 5.80 mmol) and DMAP (60.0 mg, 0.491 mmol) were added, and the reaction mixture was heated at 63 °C for 3.0 h. The solvent was then removed, and the residue was submitted to flash chromatography (column prepared with dichloromethane eluent 10-25% EtOAc/ hexanes) to give a pale-yellow foam of 917 containing traces of an impurity (349 mg, 71%). This material was suitable for further experiments. A sample of 917 was purified by radial chromatography (EtOAc/dichloromethane, 3 97) for characterization purposes [a] D = +36.0 (c = 0.540, chloroform). 

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