Crystal structure of (+)-methyl (E)-3-[(2S,4S,5R)-2-amino-5-hydroxymethyl-2-trichloromethyl-1,3-dioxolan-4-yl]-2-methylprop-2-enoate

In the title compound, intramolecular hydrogen bonding between the hydroxy and amino groups forms an S(7) graph-set motif. In the crystal, an intermolecular O—H⋯O hydrogen bond connects molecules into a dimer. The dimers are further linked into a sheet structure.


Chemical context
The 3,3-sigmatropic rearrangement of an allylic trichloroacetimidate (Overman rearrangement;Overman, 1974Overman, , 1976 is one of the most important reactions in organic chemistry. It has been utilized as a quite powerful tool to introduce the nitrogen functional group because this imidate is easily available from an allylic alcohol with trichloroacetonitrile (Cl 3 CC N). In the case of a diol, a cyclic orthoamide (2amino-2-trichloromethyl-1,3-dioxolane) may be afforded by controlling the reaction conditions though bis-imidates are usually produced. We have explored the rearrangement of the cyclic orthoamide prepared from a contiguous diol or triol, and have developed a novel strategy for the total synthesis of certain natural products (Nakayama et al., 2013). As part of our ongoing studies in this area, we now describe the synthesis and structure of the title compound.

Supramolecular features
The crystal packing is stabilized by O-HÁ Á ÁO hydrogen bonding (O12-H12AÁ Á ÁO12 i ; Table 1), connecting molecules related by a twofold rotation axis into a dimer. As the result of this intermolecular linkage, the intramolecular hydrogenbonding pattern is restricted, as shown in Fig. 3 The molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability levels. Only H atoms connected to O, N and chiral C atoms are shown for clarity. Other possible positions of disordered atoms have been omitted.

Figure 3
A pair of molecules showing a correlation between the intra-and intermolecular hydrogen bonds.

Synthesis and crystallization
The title compound was derived from d-erythrose, which was prepared according to the reported procedure (Storz et al., 1999) from d-glucose (Yasushima et al., 2016). Purification was carried out by silica gel column chromatography, and colourless crystals were obtained from a toluene solution by slow evaporation at ambient temperature. M.p. 365-366 K. [] 20 D + 33.8 (c 0.32, CHCl 3 ).
isotropically with U iso (H) = 1.5U eq (O) and the O-H distances restrained. The N-bound hydrogen atoms have three possible positions. They were refined isotropically with U iso (H) = 1.2U eq (N) and the N-H and HÁ Á ÁH distances restrained. The site-occupation factors of the disordered H atoms of the hydroxy group (H12A and H12B) and one of the amino group (H6A) were uniquely assigned to 0.5 each based on the two possible patterns of the hydrogen-bonding linkages related by the twofold axis. The occupation factors of the other N-bound H6B and H6C atoms were assumed to be 0.75 each from a difference map.   program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010) and PLATON (Spek, 2009).