Abstract
The title compound, C21H25NO3, crystallized as a racemic twin in the Sohnke space group P21. In the mol-ecular structure of the title compound, both enanti-omers show a highly similar conformation with the urethane function and the benzoyl group showing an almost perpendicular arrangement [the dihedral angle is 72.46 (8)° in the S-enanti-omer and 76.21 (8)° in the R-enanti-omer]. In the crystal structure, mol-ecules of both enanti-omers show infinite helical arrangements parallel to the b axis formed by weak C-H⋯O hydrogen bonds between the phenyl ring of the benzoyl group and the carbamate carbonyl group. In case of the R-enanti-omer, this helix is additionally stabilized by a bifurcated hydrogen bond between the carbonyl function of the benzoyl group towards both phenyl groups of the mol-ecule.
Highlights
Phenacyl and desyl compounds may act as photoremovable protecting groups (PPGs) and have been a subject of interest for many years (Givens et al, 2012; Kammari et al, 2007; Klan et al, 2013; Sheehan & Umezawa, 1973)
In the molecular structure of the title compound, both enantiomers show a highly similar conformation with the urethane function and the benzoyl group showing an almost perpendicular arrangement [the dihedral angle is 72.46 (8) in the S-enantiomer and 76.21 (8) in the R-enantiomer]. Molecules of both enantiomers show infinite helical arrangements parallel to the b axis formed by weak C—HÁ Á ÁO hydrogen bonds between the phenyl ring of the benzoyl group and the carbamate carbonyl group
Molecules of both enantiomers show infinite helical arrangements parallel to the b axis formed by weak C—HÁ Á ÁO hydrogen bonds (Desiraju & Steiner, 2001; Figs. 2 and 3) between the phenyl ring of the benzoyl group and the carbamate carbonyl group (S-enantiomer: C12A— H12AÁ Á ÁO3A, R-enantiomer: C14B—H14BÁ Á ÁO3B; Table 1)
Summary
Phenacyl and desyl compounds may act as photoremovable protecting groups (PPGs) and have been a subject of interest for many years (Givens et al, 2012; Kammari et al, 2007; Klan et al, 2013; Sheehan & Umezawa, 1973). We chose a different procedure to synthesize the title compound, according to a synthetic route that has already been reported by Speckmeier et al (2018). In case of the S-enantiomer, the carbamate and the benzoyl planes subtend a dihedral angle of 77.46 (8) whereas for the R-enantiomer an angle of 76.21 (8) is observed (Fig. 1). These angles show a higher deviation from a perpendicular arrangement than was observed for 2-oxo-2phenylethyl diisopropylcarbamate (Martens et al, 2021), most probably caused by the enhanced steric requirements of the phenyl substituent at C2A or C2B, respectively. N1A [1.354 (7) A ], C3A—O2A [1.360 (7) A ], C3B—N1B [1.350 (7) A ] and C3B—O2B [1.363 (6) A ] being slightly shorter than a typical C—O or C—N single bond due to the partial double-bond character of the respective bonds in a carbamate
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