Purification of highly polar compounds using Silica gel as solid support and methanol as main eluting agent always creates some complications.All Info About Chemistry, Jul 2008

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Used for the detection of alkaloids in natural products.

Mayer’s reagent is freshly prepared by dissolving a mixture of mercuric chloride (1.36 g) and of potassium iodide (5.00 g) in water (100.0 ml).

Most alkaloids are precipitated from neutral or slightly acidic solution by Mayer’s reagent (potassiomercuric iodide solution) to give a cream coloured precipitate.

Method A: 5.5 mmol of CDI was added to the solution of 5 mmols of N-formyl-L or D-amino acid in 2 ml of DMF. The mixture was stirred for 15 min until the CO2 formation was stopped, and the solution obtained was added to 0.2 mmols of nucleotide (disodium salt) in 2 ml of water. The reaction mixture was stirred for 2.5 hr at room temperature and diluted with 80ml of cold acetone.

After centrifugation the solid residue was washed with cold acetone and dried in vacuo. The precipitate was dissolved in 1-2 ml of deionized water and applied to the silica gel column 25×1.5 cm. Elution was made with System 2 at 4^o , 30 ml / hr. The fractions containing formylamino acod esters of nucleotides were diluted with 2 volumes of ether, and the substances were extracted three times with 0.1 volume of water. The aqous solution was shaken with ether and freeze dried. The yields and certain characteristics of the obtained compound are presented in the original paper.

Method B: N-(N’-formyl)-aminoacyl-imidazole, prepared from 2 mmols of N-formylamino acid in 2 ml of DMF as described above, was added to the nucleotide solution in 3 ml of dry formamide. The reaction mixture was stirred overnight and then diluted with 50 ml of dry acetone and 50 ml of ether, the isolation of the compound was carried out analogously to method A.

Nucleic acid research Volume 4, Number 7, July 1977, 2233-

PNA is nucleic acid (DNA or RNA) mimic. It is called as Peptide Nucleic Acid or Polyamide Nucleic Acid. PNA has a a neutral Peptide-Like backbone to which nucleobases are attached. Speaking more precisely PNAs are the mimics of Nucleic Acids that contain a pseudo-peptide backbone composed of charge neutral and achiral N-(2-aminoethyl) glycine units to which the nucleobases are attached via a methylene carbonyl linker.

The structure of a PNA is similar to a DNA oligomer. However, there is a backbone of amide bonds instead of phosphodiester backbone. Following image from University of Colorado explains the chemical difference in structure between DNA and PNA.

Image courtesy: Colorado University

The Dragendorff’s Reagent is used for the detection of Nitrogenous compounds, alkaloids, antiarrhythmic drugs and surfactants and is also good detector for Phenols.

There are two kinds for preparations, each procedure says preparation of Solution A and Solution B, both are then mixed to use.

1st Method:

Solution A: 1.7 g basic bismuth nitrate in 100 ml water/acetic acid (4:1).

Solution B: 40.0 g potassium iodide in 100 ml of water.

Mix reagents together as follows: 5 ml A + 5 ml B + 20 ml acetic acid + 70 ml water.

Spray plates, orange spots develop. Spots intensify if sprayed later with HCl, or 50% water-phosphoric acid. Good for phenols.

2nd Method:
Solution A: 1.7 g basic bismuth nitrate and 20 g tartaric acid in 80 ml of water.
Solution B: 16 g potassium iodide in 40 ml of water.

Stock solution: (stable several weaks in a refrigerator): mix equal volumes of solutions A and B
Procedure: Spray with a solution of 10 g tartaric acid, 50 ml water & and 5 ml stock solution.