2-(tert-Butoxycarbonylamino)-6-(1,3-dioxo-1H-2,3-dihydrobenzo[de]isoquinolin-2-yl)hexanoic acid

In the title naphthalimide derivative, C23H26N2O6, the 1,8-naphthalimide system is essentially planar [maximum deviation = 0.0456 (16) Å]. A characteristic pattern of alternating long and short C—C bond lengths is observed in the 1,8-naphthalimide unit. The mean planes through the methyl carbamate and acetic acid groups form dihedral angles of 42.30 (9) and 61.59 (9)°, respectively, with the 1,8-naphthalimide plane. In the crystal structure, intermolecular O—H⋯O and C—H⋯O hydrogen bonds link neighbouring molecules, forming R 2 2(9) hydrogen-bond ring motifs. These rings are further interconnected by intermolecular N—H⋯O and C—H⋯O hydrogen bonds into a three-dimensional supramolecular network.

In the title naphthalimide derivative, C 23 H 26 N 2 O 6 , the 1,8naphthalimide system is essentially planar [maximum deviation = 0.0456 (16) Å ]. A characteristic pattern of alternating long and short C-C bond lengths is observed in the 1,8naphthalimide unit. The mean planes through the methyl carbamate and acetic acid groups form dihedral angles of 42.30 (9) and 61.59 (9) , respectively, with the 1,8-naphthalimide plane. In the crystal structure, intermolecular O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link neighbouring molecules, forming R 2 2 (9) hydrogen-bond ring motifs. These rings are further interconnected by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds into a three-dimensional supramolecular network.
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 (Pogozelski & Tullius, 1998). They have a diversity of reactivity towards biological substrates (Pogozelski & Tullius, 1998). 1,8-Naphthalimide derivatives have attracted significant attention due to not only their participation in photoinduced electron transfer (PET) processes (Le et al., 2000;Abraham et al., 2004), but also to their applications in the fields of biology and medicine (Saito et al., 1995a). Some 1,8-naphthalimide derivatives have been reported to inhibit virulence regulation in Vibrio cholerae by inhibiting the transcriptional regulator ToxT (Hung et al., 2005). Other 1,8-naphthalimide derivatives have also been used in the photosensitized one-electron oxidation of DNA through the PET process (Saito et al., 1995b). In view of the importance of the 1,8-naphthalimide derivatives, the title compound was obtained and this paper reports its crystal structure.

Experimental
The title compound was derived from the reaction between 1,8-naphthalic anhydride and α-N-Boc-L-Lysine in anhydrous dimethylformamide. Removal of the solvent under reduced pressure followed by silica gel chromatography gave the title compound. X-ray quality single crystals of the tile compound were obtained from slow evaporation of a methanol/ether solution (1:2, v:v).

Refinement
Atoms H1N2 and H1O6 were located from difference Fourier map and allowed to refine freely. All other hydrogen atoms were placed in their calculated positions, with C-H = 0.93 -0.97 Å, and refined using a riding model, with U iso = 1.2 or supplementary materials sup-2 1.5 U eq (C). A rotating group model was used for the methyl groups. In the absence of significant anomalous dispersion, 2210 Friedel pairs were merged for the final refinement. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.