Chromatography preparation, dipping

Method. The amino acid derivatives are prepared by adding disyl chloride (1 mg/ml in acetone) to an equal volume of a solution of the amino acid (ca. 5 10 4 jumoles/ml in 0.1 M sodium bicarbonate solution). The reaction is allowed to proceed for 3 h at room temperature. The solvent is evaporated and the residue is dissolved in 1 ml of acetone-methanol (1 1) for application to a thin-layer plate of silica gel. A number of solvent systems used for the separation of amino acid derivatives is given in Table 4.14. After chromatography, the plates are dried at 10S °C for S min, cooled to room temperature and dipped in a solution of sodium ethoxide (S g of sodium per 100 ml of 96% ethanol). The plate is observed immediately under UV light at 365 nm. The amino acid derivatives appear yellow-green. 

Treatment of 6.6 equivalents of the corresponding boron enolate of 6, [prepared by treatment of 6 with (+)-B-chlorodiisopinocampheylborane (DIP-Cl), 63, and triethylamine in diethyl ether at 0 °C], followed by aldol addition with cw-a,p-unsaturated aldehyde 8 at -78 °C, led to alcohol 64a in 50-55% yield after chromatography on reverse-phase silica gel, together with its epimer 64b in a ratio of 4 1 (Scheme 10). 

Opiates can be identified by thin-layer chromatography (TLC) with many different combinations of mobile-phase solvent systems and detection reagents. A solvent system prepared with ethyl ace-tate-methanol-ammonium hydroxide (85 10 5) is commonly used to resolve heroin, codeine, acetylco-deine, morphine, and acetylmorphine. After development, opiates can be visualized by spraying or dipping the chromatogram in Dragendorff, iodoplatinate, or Marquis reagent. 

The lower portion of the trap was removed and the inlet tube and dip leg were washed with water into the lower tube. The final volume was adjusted to 2 ml. The aqueous solution was analyzed by gas chromatography for alcohol content. Mixtures containing methanol, ethanol, and isopropanol were readily resolved. Standard solutions of alcohol in water at 5 to 1400 y g/ml were prepared and chromatographed under identical conditions. Peak heights were measured and used to construct a linear calibration curve of peak height vs. alcohol concentration. From this curve, the amount of each alcohol derived from alkoxy present was determined. Percent alkoxy was then calculated using appropriate dilution and weight conversion. 

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