(S S,2S,3S)-2-(2-Methylpropan-2-sulfinamido)-3-phenylbutyronitrile

The absolute configuration has been determined for the title compound, C14H20N2OS. There are two independent molecules in the asymmetric unit. Intermolecular N—H⋯O hydrogen bonds are observed in the crystal packing, forming infinite chains with the base vectors [100] and [010]. Each chain contains only one of the two independent molecules.

The absolute configuration has been determined for the title compound, C 14 H 20 N 2 OS. There are two independent molecules in the asymmetric unit. Intermolecular N-HÁ Á ÁO hydrogen bonds are observed in the crystal packing, forming infinite chains with the base vectors [100] and [010]. Each chain contains only one of the two independent molecules.

( S S,2S,3S)-2-(2-Methylpropan-2-sulfinamido)-3-phenylbutyronitrile
K. Harms, M. Marsch, M. Oberthür and P. Schüler Comment Chiral sulfinimines have proven to be powerful and versatile precursors for the synthesis of nonproteinogenic amino acids (Ferreira et al., 2008). They allow the stereoselective introduction of cyanide therefore representing an asymmetric modification of the Strecker reaction (Davis et al., 1994); Li et al., 2003). We have synthesized the title compound, (I), that can be hydrolyzed to give (2S,3S)-β-methylphenylalanine which is an amino acid found in the antibiotic families of the bottromycins and the mannopeptimycins (Singh et al., 2003); Kaneda, 1992;and Kaneda, 2002). In this paper we report the crystal structure and absolute configuration of (I).
The molecular structure of (I) is presented in Fig. 1. There are two independent molecules in the asymmetric unit. The structure exhibits intermolecular N-H···O hydrogen bonds resulting in infinite one dimensional chains with the base vectors [1 0 0] and [0 1 0], respectively (details have have been provided in Table 1 and Fig. 2). Each chain contains only one of the two independent molecules.
The crystal structure and absolute configuration of a closely related compound has just been reported (Harms et al., 2009).

Refinement
The amino H atoms were isotropically refined with a restraint (0.85 Å) N-H distance. The other H atoms were positioned geometrically (C-H = 0.95-1.00 Å) and allowed to ride on their parent atoms, with 1.5 U eq (C methyl ) or 1.2 U eq (C).

Special details
Experimental. ν max /cm -1 3232 ( 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.