title: (2S)-2-(4-Ethyl-2,3-dioxopiperazine-1-carboxamido)-2-(4-hy-droxy-phen-yl)acetic acid.
abstract: There are two mol-ecules in the asymmetric unit of the title compound, C(15)H(17)N(3)O(6). The 2,3-dioxopiperazine ring adopts a half-chair conformation with torsion angles of -7.6 (4) and 35.1 (4)° in one mol-ecule, and 5.3 (4) and 45.4 (4)° in the other mol-ecule. In the crystal structure, the carb-oxy groups are involved in classical inversion-related O-H⋯O hydrogen bonds, which link the mol-ecules into centrosymmetric dimers. These dimers are further linked by inter-molecular O-H⋯O and C-H⋯O hydrogen bonds. Each independent mol-ecule also exhibits an intra-molecular N-H⋯O hydrogen bond. The H atoms of the carb-oxy groups are disordered over two positions, with refined site-occupancy factors of 0.5.
authors: Department of Chemistry, Shandong Normal University, Jinan 250014, People's Republic of China.
authors: Qian
authors: Q
authors: Wang
authors: Ling
authors: L
authors: Hu
authors: Jian-Ping
authors: JP
authors: Ma
authors: Dian-Shun
authors: DS
authors: Guo
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