Protected forms of dihydroxyphenylalanine (DOPA) were converted to the corresponding dihydroquinolin-2-ones 13 by nitration and reductive cyclization. Subsequent N-alkylation with 0-halo-7-aminobutryic acid derivatives provided the carbon framework 12 for the chromophore of pseudobactin. Conversion to protected forms of the fluorescent chromophore 5 was accomplished by reaction of 12 with Lawesson's reagent to produce ...
