Enantioselective synthesis of tri-deuterated (-)-geosmin to be used as internal standard in quantitation assays.

For the accurate and sensitive quantitation of the off-flavor compound geosmin, particularly in complex matrices, a stable isotopologue as internal standard is highly advantageous. In this work, we present a versatile synthetic strategy leading from (4aR)-1,4a-dimethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one to tri-deuterated (-)-geosmin ((4S,4aS,8aR)-4,8a-dimethyl(3,3,4- H )octahydronaphthalen-4a(2H)-ol). The starting material was readily accessible from inexpensive 2-methylcyclohexan-1-one using previously published procedures.