(R)-2-Benzyl-4-methylpentyl (R)-2-methoxy-2-(1-naphthyl)propionate

The relative configuration of the alcohol component in the title ester, C27H32O3, has been assigned as (R) from the known configuration of (R)-(−)-2-methoxy-2-(1-naphthyl)propionic acid [(R)-MαNP acid]. In the crystal structure, the C atom of the methyl group of the MαNP acid lies in the extended plane of the naphthyl ring system [methyl C atom deviates from plane by 0.211 (2) Å; r.m.s. deviation of fitted atoms = 0.0187 Å] and a weak intramolecular C—H⋯O hydrogen bond links the naphthyl ring system and the methoxy group. These structural properties are similar to those of most MαNP acid esters.

The relative configuration of the alcohol component in the title ester, C 27 H 32 O 3 , has been assigned as (R) from the known configuration of (R)-(À)-2-methoxy-2-(1-naphthyl)propionic acid [(R)-MNP acid]. In the crystal structure, the C atom of the methyl group of the MNP acid lies in the extended plane of the naphthyl ring system [methyl C atom deviates from plane by 0.211 (2) Å ; r.m.s. deviation of fitted atoms = 0.0187 Å ] and a weak intramolecular C-HÁ Á ÁO hydrogen bond links the naphthyl ring system and the methoxy group. These structural properties are similar to those of most MNP acid esters.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZS2041).

Comment
In a previous paper, we reported that (S)-2-methoxy-2-(1-naphthyl)propionic acid [(S)-MαNP acid] is an efficient auxiliary for enantioresolution of racemic secondary alcohols and the simultaneous determination of the absolute configuration of the resolved alcohols by the Advanced Mosher Method (Kuwahara et al., 2007). We also reported the determination of the absolute configuration of esters condensed with (S)-MαNP acid using X-ray crystallography, by comparison with the known configuration of the asymmetric quaternary carbon of the acid as an internal standard (Sekiguchi et al., 2008). We will report herein that that (R)-MαNP acid is also a useful auxiliary for the identification of remote asymmetric centers in primary alcohols.
2-Isobutyl-3-phenyl-1-propanol was enantioresolved using (R)-(-)-2-methoxy-2-(1-naphthyl)propionic acid and the absolute configuration of the alcohol component of the second fraction from the HPLC separation, the ester C 27 H 32 O 3 (I) has ( Fig. 1) been assigned as R from the known configuration of (R)-MαNP acid. In the structure of (I) there is a weak intramolecular hydrogen bond linking the naphthyl ring and the methoxy group (C13-H···O1) ( Table 1, Fig. 1) which results in the carbon atom of the methyl group lying in the extended plane of the naphthyl ring of the MαNP acid moiety. These structural properties are similar to those of most MαNP acid esters (Kuwahara et al., 2007).

Experimental
Two diastereomers were obtained from the reaction of (R)-(-)-2-methoxy-2-(1-naphthyl)propionic acid with 2-isobutyl-3phenyl-1-propanol (Kuwahara et al., 2007) and were separated by HPLC, eluting with a mixture of ethyl acetate and hexane (50:1). After removal of most of the solvent, the residual oil was allowed to stand for 6 months, giving single crystals suitable for X-ray diffraction analysis.

Refinement
In the refinement of the title compound, the H atom positions were calculated geometrically and refined as riding, with C-H bond lengths of 0.95-1.00 Å, and with U iso (H) values of 1.2U eq (aromatic C) or 1.5U eq (methyl C).
supplementary materials sup-2 Figures Fig. 1. Molecular configuration and atom numbering scheme for the title compound, with displacement ellipsoids drawn at the 50% probability level.