PREPARATION OF CHIRAL 1,2,3,4-TETRAHYDRO-6,7-DIALKOXY-3-ISOQUINOLINECARBOXYLIC ACID AND DERIVATIVES

The present invention relates to a process for the production of (S)-1,2,3,4-tetrahydro--6,7-dialkoxy-3-isoquinolinecarboxylic acid compounds (1) and their derivatives from Levodopa (L-Dopa). The ultimately prepared compounds are used as intermediat es for, but not limited to, the preparation of substituted derivatives of 1,2,3,4-tetrahydro--6,7-dialkoxy-3-isoquinolinecarboxylic acid (see formula 1) wherein R1 is hydrogen, lower alkyl, C2-C12 acyl, or R1O together are methylenedioxy ; R2 is hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl , substituted aryl, aralkyl or substituted aralkyl group; and R3 is hydrogen, C2-C12 acyl group, benzyl, alkoxylcarbonyl group, or aralkox yl carbonyl group.