Chiral 1,3-oxathiane, from -pulegone

CHIRAL 1,3-OXATHIANE FROM (+)-PULEGONE HEXAHYDRO-4,4,7-TRItCTHYL-4H-l, 3-BEN 2DXATHIIN (4H-1,3-Benzoxathiin, hexahydro-4,4,7-trimethyl-)... 

Chiral 1,3-Oxathiane from (+)-Pulegone Hexahydro-4,4,7-Trimethyl-4i/- 1,3-benzoxathiin... 

Solladie-Cavallo s group used Eliel s oxathiane 1 (derived from pulegone) in asymmetric epoxidation (Scheme 1.3) [1]. This sulfide was initially benzylated to form a single diastereomer of the sulfonium salt 2. Epoxidation was then carried out at low temperature with the aid of sodium hydride to furnish diaryl epoxides 3 with high enantioselectivities, and with recovery of the chiral sulfide 1. 

An asymmetric synthesis of mevalolactone in over 87% e.e. employs a 1,3-oxathiane as the chiral auxiliary (81TL2859). The reagent (818), easily prepared from (+)-pulegone (81TL2855), was metallated with u-butyllithium and the anion reacted with acetaldehyde. Oxidation of the diastereomeric mixture of alcohols to the ketone (819) and reaction of... 

A much more readily accessible chiral auxiliary is oxathiane 16, which can be smoothly synthesized from inexpensive (+)-pulegone (14)3S. 

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