(5R*)-5-[(2S*,5S*)-1-Methoxy-5-phenylpyrrolidin-2-yl]-3-methylfuran-2(5H)-one

In the title compound, C16H19NO3, the pyrrolidine ring is in a twist conformation. The dihedral angle between the dihydrofuran ring [maximum deviation = 0.0016 (11) Å] and the phenyl ring is 47.22 (8)°. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming helical chains along the b-axis direction. The chains are further linked by C—H⋯π interactions to constitute a three-dimensional architecture.

In the title compound, C 16 H 19 NO 3 , the pyrrolidine ring is in a twist conformation. The dihedral angle between the dihydrofuran ring [maximum deviation = 0.0016 (11) Å ] and the phenyl ring is 47.22 (8) . In the crystal, molecules are linked by weak C-HÁ Á ÁO hydrogen bonds, forming helical chains along the b-axis direction. The chains are further linked by C-HÁ Á Á interactions to constitute a three-dimensional architecture.

Comment
A number of compounds containing oxidized nitrogen functionality have been widely used in organic synthesis. In these substances, the N-alkoxyamines are known as the initiators for the stable free radical polymerization (Hawker et al., 2001), and the N-alkoxyamides are utilized for mild and effective acylating agents (cf. Weinreb amide; Nahm & Weinreb, 1981). We noticed this inert N-O covalent bond, to develop a novel reaction to synthesize the natural alkaloids (Yanagita et al., 2013).

Refinement
C-bound H atoms were positioned geometrically with C-H = 0.95-1.00 Å, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). The Friedel opposites were merged before the final refinement because no significant anomalous dispersion was observed and the Flack parameter was a meaningless value of -1.2 (10) with 1054 Bijvoet pairs. One reflection (7 3 4) has been omitted in the final refinement.

Figure 1
The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.

Figure 2
The crystal packing of the title compound, viewed down the a axis. Dashed lines indicate the intermolecular C5-H···O6 interactions, making helical chains along [010]. Only H atoms involved in hydrogen bonds were shown for clarity.

Crystal data
C 16 H 19 NO 3 M r = 273.32 Orthorhombic, P2 1 2 1 2 1 a = 6.5427 (3)  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.