Patent ID: 8344176

Claim:
A process for the preparation of a compound of formula (I) wherein R is hydrogen, a straight or branched C 1 -C 6 alkylcarbonyl group or a phenylcarbonyl group, or a salt thereof, characterized by the steps of a) reacting a compound of formula (II) with a mixture of Mg and a Grignard initiator of the formula R1MgX, wherein R1 represents C 1 -C 12 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, substituted or unsubstituted phenyl or phenyl(C 1 -C 6 )alkyl, and wherein X is selected from bromide, chloride and iodide to form a Grignard reagent, and c) reacting the Grignard reagent with an excess of a carbonate selected from the group of di(C 1 -C 6 alkyl) carbonates and cyclic C 1 -C 6 alkylene carbonates to obtain a compound of formula (III) wherein A is a C 1 -C 6 alkyl group, and then further reacting the compound of formula (III) to obtain a compound of formula (I).