γ‑Turn Mimicry with Benzodiazepinones and Pyrrolobenzodiazepinones Synthesized from a Common Amino Ketone Intermediate

To investigate diazepinone analogues
as γ-turn mimics, seven
1,4-benzodiazepin-2-ones 6 and fourteen pyrrolo­[1,2-d]­[1,4]­benzodiazepin-6-ones 4 and 5 were synthesized from 1-(2-aminophenyl)­pent-4-en-1-one (7). Acylation of aniline 7 with N-Boc-amino
acids, olefin oxidation, Boc removal, and intramolecular Paal–Knorr
condensation gave 4 and 5. Alternatively,
Boc removal prior to oxidation gave benzodiazepinones 6, which were converted to 4 by ozonolysis and cyclization.
Comparison of dihedral angle values for the amino acid component from
X-ray analyses of 4g, 5f, and 6f and related diazepinones has catalogued the manner by which ring
substituents affect the component’s ability to mimic the central
residues of γ-turns.