PREPARATION OF CHIRAL 1,2,3,4-TETRAHYDRO-6,7-DIALKOXY-3-ISOQUINOLINECARBOXYLIC ACID AND DERIVATIVES BY REACTING LEVODOPA WITH FORMALDEHYDE OR FORMALDEHYDE PRECURSORS

摘要

A process for preparation of (S)-1,2,3,4-tetrahydro-6,7-dialkoxy-3-isoquinolinecarboxylic acid compounds and their derivatives of the formula (1) the process compring: (i) reacting Levodopa of formula (2) with formaldehyde or formaldehyde precursors to obtain (S)-1,2,3,4-tetrahydro-6,7-dihydroxy-3-isoquinolinecarboxylic acid of formula (3); (ii) protecting the amino group of formula (3); (iii) alkylating the phenol groups of formula (4) to form compound of formula (5); and (iv) esterifying the carcoxylic acid of formula (5) and optionally removing N-protecting group 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; R3 is hydrogen, C2-C12 acyl group, benzyl, alkoxylcarbonyl group, or aralkoxyl carbonyl group; wherein P is the protecting group selected from alkoxycarbonyl, acyl, alkyl, aryl, siryl, sulfenyl and sulfonyl.