Crystal Structure of N-Acetylkynurenine

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Abstract
The crystal structure of N-acetylkynurenine [o-NH2C6H4COCH2CH(COOH)NHCOCH3] was determined by direct methods. The crystals are monoclinic, a 11.200(2), b 9.708(1), c 11.451(1) .ANG., .beta. 90.16(2).degree., space group P21, with Z4. The structure was refined by least squares to R 0.033 with 1909 unique reflections, collected on an automated 4-circle diffractometer. The structure is similar to the related L-trytophan hydrochloride. The 2 molecules in the asymmetric unit (A,B) are generally similar structurally but differ slightly in the conformation of the N-acetyl chain, which has dihedral angles with the plane of the benzene ring of 78.0.degree. (A) and 81.5.degree. (B). Torsion angles about the C(.alpha.).sbd.C(.BETA.) bond between C(.gamma.) and both the carboxyl and the amino groups make them mutally gauche. There is an extensive H-bonding system between the 2 distinct molecules and between similar molecules either to form a dimer or a linear polymer.

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