restricted amino acids
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Summary During a study on the preparation of the conformationally restricted analogue of tryptophan into 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid1 by a Pictet-Spengler condensation with formaldehyde, two site products were detected:N-hydroxymethyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid2 and a dimer3 of two 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid units linked by a methylene group. Their structures were determined by HPLC-MS and 2D NMR spectroscopy. By changing the isolation procedure, theN-hydroxymethyl compound was removed. Treatment of the mixture with TFA in water converted the dimer into 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid1.
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