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