PATIC: a conformationally constrained photoisomerizable amino acid

The synthesis of a conformationally constrained photoisomerizable amino aci d, phenylazo-1,2,3,4-tetrahydro-3-isoquinolinecarboxylic acid (PATIC), is d escribed. This amino acid can be incorporated into peptides using standard Fmoc procedures and can be accommodated within a-helical structures albeit with some loss of stability of the structure. PATIC can serve as a useful b uilding block for the synthesis of photoregulated peptides and proteins.