Amino acids, isolation picrate derivatives

The amines are isolated either by liberation from the crystalline amine sulfate, or by steam distillation of the alkalized water extract of the reaction mixture, or by ether extraction of the alkaline solution. In the preparation of amino acids the isolation may be effected by forming an appropriate derivative such as a picrate or phosphotungstate. ... 

No simple salts of 2,1 -benzisothiazole have been described in the literature, other than those of amino-substituted derivatives,101 in which the site of protonation is probably the cyclic nitrogen atom, at least in the 3-substituted compounds. The parent compound does, however, form a simple crystalline nitrate 114 which is not very stable. A number of complex salts with platinum, gold, lead, and mercury salts and with picric acid have been described.96,97,116 The picrate is highly crystalline and stable, and is useful for the isolation and characterization of 2,1-benzisothiazole. Many substituted 2,1-benzisothiazoles form similarly useful picrates.106... 

Amino-5-deoxy-D-xylopyranose (17) has the structure of a cyclic a-amino alcohol and should, accordingly, react with nucleophiles, leading to a-amino alkylation. " These reactions generally proceed under acid catalysis, and are only applicable to 17 if they provide rapid formation of stable products otherwise, rearrangement to 22 results. The condensation of 17 with o-aminobenzaldehyde at pH 5 gives the quinazolinium derivative (36), isolated as a red, crystalline picrate. This reaction serves as a specific chromatographic indicator for 16 17. 

---