2-(Tricyclo[3.3.1.13,7]dec-2-ylamino)ethanol hemihydrate

The title adamantane derivative, C12H21NO·0.5H2O, was synthesized as part of an investigation into the biological activities of cage amino–alcohol compounds as potential anti-tuberculosis agents. The structure displays intermolecular O—H⋯N, N—H⋯O, O—H⋯O hydrogen bonding and a layered packing structure with distinct hydrophilic and hydrophobic regions. The water molecule lies on a twofold rotation axis.

The title adamantane derivative, C 12 H 21 NOÁ0.5H 2 O, was synthesized as part of an investigation into the biological activities of cage amino-alcohol compounds as potential antituberculosis agents. The structure displays intermolecular O-HÁ Á ÁN, N-HÁ Á ÁO, O-HÁ Á ÁO hydrogen bonding and a layered packing structure with distinct hydrophilic and hydrophobic regions. The water molecule lies on a twofold rotation axis.

Comment
The title compound, an adamantane derivative, was synthesized as part of an ongoing study to evaluate the biological activity of such compounds as potential anti-tuberculosis agents (Bogatcheva et al. (2006), Lee et al. (2003), Tripathi et al. (2006).
Although the compound is known (du Pont de Nemours and Co.; 1969), its crystal structure has not been reported.
The compound contains a polycyclic (lipophilic) hydrocarbon region, polar amine and hydroxyl units, and crystallizes with half a water molecule in the asymmetric unit ( Fig.1)-the water molecule being situated on a crystallographic 2-fold axis at (1, y, 3/4). The title molecule exhibits several C-C bond lengths in the adamantane skeleton that deviate from the expected value of 1.54 Å. This has been observed previously and is typical for these types of compounds.
The structure exhibits intermolecular hydrogen bonding between O1 and N1 of adjacent molecules as well as between O1 and O1W of the water molecule (Fig. 2). There is also a complex network of short contacts between the molecules in structure. These intermolecular interactions result in a layered structure with distinct hydrophilic and hydrophobic regions ( Fig. 3). The adamantane skeleton forms the hydrophobic layer while the polar hydroxyl and amino moeties constitute the hydrophilic region.

Experimental
A mixture of 2-adamantanone (2 g, 13 mmol) and 2-aminoethanol (1 g, 16 mmol) in 20 ml of methanol was stirred under dinitrogen atmosphere at room temperature for 2 h. The mixture was cooled to zero degrees using an external ice bath after with NaBH 4 (1 g, 26 mmol) was added slowly over a 30 minutes. The mixture was stirred for overnight at room temperature after which it was concentrated in vacuo and excess NaBH 4 was quenched by adding 40 ml of 10% HCl and the product was also extracted as its HCl salt in the process. The aqueous solution was washed with 2x20ml of dichloromethane, after which the aqueous layer was basified (pH 12) with NH 4 OH and the product was extracted from the mixture with dichloromethane (2x30ml), the solvent was dried over Na 2 SO 4 and concentrated in vacuo. The product was recrystallized from dichloromethane, thereby affording pure 2-aminoethanol adamantane (2 g, 77% yield).

Refinement
Non-hydrogen atoms were first refined isotropically followed by anisotropic refinement by full matrix least-squares calculations based on F 2 using SHELXTL. With the exception to H1B and H1W, all hydrogen atoms were first located in the difference map then positioned geometrically, and allowed to ride on their respective parent atoms, with bond lengths of 0.99 Å (CH 2 ), 1.00 Å (Methine CH) or 0.84 Å (OH). Isotropic displacement parameters for these atoms were set equal to 1.2 (CH 2 and CH), or 1.5 OH) times U eq of the parent atom. Atoms H1B and H1W were located in the difference map and refined freely.