Stereoselective synthesis of 1,4-benzodiazepines via photoinduced decarboxylation of N-phthaloylanthranilic acid amides

Photochemical decarboxylation of amides derived from N-phthaloylanthranilic acid coupled to a series of alpha -amino acids under basic conditions resulted in 1,4-benzodiazepines (from sarcosine, alanine, valine, leucine, phenylalanine, aspartic and glutamic acid) and several annulated (from 2-azetidine and pipe-colinic acid, proline and 2-azabicyclo[3.3.0]undecanoic acid) 1,4-benzodiazepines 1c-12c in good yields (except for 6c and 7c from acidic amino acids and 9c) and excellent diastereoselectivities. Also quaternary alpha -amino acids could be applied as demonstrated for the alpha -amino isobuyrate derivative 8b. Optically active substrates 9b, 10b, 10e, 12b, and 12e were converted into non-racemic products with a high degree of chirality memory with (inversion of configuration at the stereogenic center) and ee-values of > 79 %. The corresponding 4-chlorinated products 1e-12e were obtained in comparable yields from the 4-chloroanthranilic acid-derived substrates.