Ethanolamine blocking aldehydes

Figure 1.124 Aldehyde groups may be blocked with Tris or ethanolamine using a reductive amination process.

To block unreacted aldehyde sites, add 20 pi of 3 M ethanolamine (pH adjusted to desired value with HC1) per ml of the conjugation solution volume. React for 15 minutes at room temperature. 

Block unreacted aldehydes by the addition of 50 pi of 1M ethanolamine, pH 7.5, per ml of reaction solution. Block for 30minutes at room temperature with mixing. 

Add to the particle suspension a quenching molecule (such as glycine, ethanolamine, or Tris) to give a final concentration of 0.2 M. The blocking agent will couple to any remaining aldehyde-reactive sites. 

Block unreacted aldehyde sites by addition of 50 pi of 1M ethanolamine, pH 9.6, per ml of conjugation solution. Approximately a 1M ethanolamine solution may be prepared by addition of 300 pi ethanolamine to 5 ml of deionized water. Adjust the pH of the ethanolamine solution by addition of concentrated HC1, while keeping the solution cool on ice. 

Block unreacted aldehyde sites by addition of 50 pi of 1 M ethanolamine, pH... 

Besides the use of stereoselective nitrile-converting enzymes as described above, useful chiral building blocks have also been obtained by stereoselective nitrile-forming enzymes. The main product class of nitrile-forming enzymes are cyanohydrins (a-hydroxynitriles, 1-cyanoalkanols), which are versatile synthons in organic synthesis that are readily convertible to a-hydroxy acids [90], a-hydroxy aldehydes [91], ethanolamines [92], amino alcohols, pyrethroid insecticides [93], imidazoles, and heterocycles [94]. Examples of valuable bioactive products derived from chiral cyanohydrins are (i )-adrenaline, L-ephedrin, and (5)-amphetamines [95]. For the synthesis of chiral cyanohydrins, stereoselective enzymes from both plant and bacterial sources have been used. 

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