tert-Butyl N-[2-(N-isobutyl-4-methoxybenzenesulfonamido)ethyl]carbamate

The title compound, C18H30N2O5S, was synthesized by the reaction of tert-butyl 2-(isobutylamino)ethylcarbamate with p-methoxyphenylsulfonyl chloride. In the molecule, two intramolecular C—H⋯O hydrogen bonds are observed. In the crystal, molecules are linked by N—H⋯O hydrogen bonds involving the imino group N atom and the ester group O atom into chains running parallel to the b axis. The chains are further connected by C—H⋯O hydrogen bonds, forming layers parallel to the bc plane.

The title compound, C 18 H 30 N 2 O 5 S, was synthesized by the reaction of tert-butyl 2-(isobutylamino)ethylcarbamate with pmethoxyphenylsulfonyl chloride. In the molecule, two intramolecular C-HÁ Á ÁO hydrogen bonds are observed. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds involving the imino group N atom and the ester group O atom into chains running parallel to the b axis. The chains are further connected by C-HÁ Á ÁO hydrogen bonds, forming layers parallel to the bc plane.

Comment
As a part of our ongoing project aimed at the development of potential HIV-1 protease inhibitors (Surleraux et al., 2005;Ghosh et al., 2006Ghosh et al., , 2011Guo et al., 2010), we have synthesized the title compound and report its crystal structure herein.
The molecular structure of the title compound is illustrated in Fig. 1. Bond distances and angles are similar to those found in the methoxy analogue (Chatziefthimiou et al., 2006). The molecular conformation is stabilized by two intramolecular C-H···O hydrogen bonds (Table 1). In the crystal, the molecules are linked into chains by intermolecular N-H···O hydrogen bonds (Table 1) parallel to the b axis ( Fig. 2), which are further connected to form layers parallel to the bc plane by C-H···O hydrogen bonds (Table 1).
The yield is 42%. Colourless block crystals suitable for X-ray diffraction were obtained in 3 day by slow evaporation of a petroleum ether/AcOEt (4:1 v/v) solution.

Refinement
All H atoms could be detected in a difference Fourier map. The H atom bonded to N2 was refined freely, all other Hatoms were placed in calculated positions and refined using a riding motion approxmation, with C-H = 0.93-0.97 Å, and with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl H atoms.  The molecular structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.