Stereoselective Synthesis of 1,4-Benzodiazepines via Photoinduced Decarboxylation of N-Phthaloylanthranilic Acid Amides

Abstract

Photochemical decarboxylation of amides derived from N-phthaloylanthranilic acid coupled to a series of α-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 pipecolinic 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 α-amino acids could be applied as demonstrated for the α-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.

Key words

photochemistry - photodecarboxylation - photoinduced electron transfer - benzodiazepines - pyrrolo[1,4]benzodiazepines - triplet biradicals - radical combination - stereoselectivity - memory of chirality

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Görner, H.; Oelgemöller, M.; Griesbeck, A. G. J. Phys. Chem. A, submitted.