1-(2-Hydroxy-2-phenylethyl)-3-(4-methoxyphenyl)urea

In the title compound, C16H18N2O3, the dihedral angle between the 4-methoxyphenyl ring and the urea group is 35.6 (2) °. The H atoms of the urea NH groups are positioned syn to each other. In the crystal, intermolecular N—H⋯O and O—H⋯O hydrogen bonds link the molecules into a two-dimensional array in the ac plane; the carbonyl-O atom is trifurcated.

In the title compound, C 16 H 18 N 2 O 3 , the dihedral angle between the 4-methoxyphenyl ring and the urea group is 35.6 (2) . The H atoms of the urea NH groups are positioned syn to each other. In the crystal, intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the molecules into a twodimensional array in the ac plane; the carbonyl-O atom is trifurcated.
We wish to thank the DBIO company for partial support of this work.

Comment
Melanin is one of the most widely distributed pigments and is found in bacteria, fungi, plants and animals. It is a heterogeneous polyphenol-like biopolymer with a complex structure and colour varying from yellow to black (Prota, 1988). Tyrosinase inhibitors are clinically useful for the treatment of some dermatological disorders associated with melanin hyperpigmentation and are also important in the cosmetic industry for whitening and depigmentation after sunburn (Khan et al., 2006). Numerous potential tyrosinase inhibitors have been discovered from natural and synthetic sources, such as ascorbic acid (Kojima et al., 1995), kojic acid (Cabanes et al., 1994), and tropolone (Son et al., 2000;Iida et al., 1995). But some of their individual activities are either not potent enough to be considered of practical use or not compatible with safety regulations for food and cosmetic additives. In our continuing search for tyrosinase inhibitors, we have synthesized the title compound, (I), from the reaction of 2-amino-1-phenylethanol and 4-methoxyphenyl isocyanate under ambient conditions.
Herein, the crystal structure of (I) is described (Fig. 1).
The 4-methoxyphenyl unit is almost planar, with an r.m.s. deviation of 0.031 Å from the least-squares plane defined by the eight constituent atoms. The dihedral angle between the 4-methoxyphenyl ring and the urea plane is 35.6 (2) °. The H atoms of the urea NH groups are positioned syn to each other. The presence of intermolecular N-H···O and O-H···O hydrogen bonds link the molecules into a two-dimensional array in the ac plane ( Fig. 2, Table 1). The urea-O accepts three hydrogen bonds, one from -OH and two from -NH groups.
Experimental 2-Amino-1-phenylethanol and 4-methoxyphenyl isocyanate were purchased from Sigma Chemical Co. All other chemicals and solvents were of analytical grade and were used without further purification. The title compound (I) was prepared from the reaction of 2-amino-1-phenylethanol (0.3 g, 1.2 mmol) with 4-methoxyphenyl isocyanate (0.39 g, 1.0 mmol) in acetonitrile (6 ml) with stirring. The reaction was completed within 1 h at room temperature. The solvents were removed under reduced pressure, collected and washed with dichloromethane. Removal of the solvent gave a white solid (84%; M.pt 468 K). Colourless crystals of (I) were obtained from its ethanolic solution by slow evaporation of the solvent at room temperature.