4-[(tert-Butyldimethylsilyl)oxy]-6-methoxy-7-methyl-5-(oxiran-2-ylmethyl)-2-benzofuran-3(1H)-one

The title compound, C19H28O5Si, was obtained in the reaction of 1,3-dihydro-4-[(tert-butyldimethylsilyl)oxy]-6-methoxy-7-methyl-3-oxo-5-(prop-2-enyl)isobenzofuran with meta-chloroperbenzoic acid. This reaction is one of the stages of the total synthesis of mycophenolic acid, which we attempted to modify. The title compound forms crystals with only weak intermolecular interactions. The strongest stacking interaction is found between the benzene and furan rings of inversion-related molecules with a distance of 3.8773 (13) Å between the ring centroids.

The title compound, C 19 H 28 O 5 Si, was obtained in the reaction of 1,3-dihydro-4-[(tert-butyldimethylsilyl)oxy]-6-methoxy-7methyl-3-oxo-5-(prop-2-enyl)isobenzofuran with meta-chloroperbenzoic acid. This reaction is one of the stages of the total synthesis of mycophenolic acid, which we attempted to modify. The title compound forms crystals with only weak intermolecular interactions. The strongest stacking interaction is found between the benzene and furan rings of inversionrelated molecules with a distance of 3.8773 (13) Å between the ring centroids.

Comment
Presented research is an attempt to modify the known multi-stage total synthesis of mycophenolic acid (Patterson, 1995) by making use of epoxides as intermediates. The synthesis of the desired epoxide was successful and its X-ray structure has been determined.
The crystal lattice is composed of discrete molecules with no strong specific intermolecular interactions. The strongest stacking interaction is found between the benzene and furan rings of molecules related by the inversion at (1/2, 1/2, 1) with a distance of 3.8773 (13) Å between the ring centroids.
The ORTEP view of the title epoxide is given in Fig. 1. Although the oxirane ring is not connected with the aromatic ring directly, the shortest intramolecular contact between the ring and adjacent methoxy substituent is rather short 2.560 (3) Å for O5···H11A. Epoxides are known to be reactive compounds (Padwa et al., 2006), but the investigated oxirane is relatively stable and can be purified on silica gel and stored for several months. We suppose the reactivity of the epoxide ring is decreased by the steric hindrance from the proximate methoxyl and t-BuMe 2 Si substituents.
isobenzofuran, was carried out based on the procedure reported in the chemical literature (Plé et al., 1997).
We applied lower temperature for addition of m-CPBA (-70 °C, instead of -30 °C), and then the reaction was carried out at room temperature (instead of 0 °C).
Single crystals were obtained by vapour diffusion of petroleum ether into a solution of about 30 mg product in 1 mL dichloromethane over 3-4 days (m.p. 96-98 °C).