New and convenient synthesis of 2, 3, 9, 10-tetraoxygenated protoberberine alkaloids and their 13-methyl alkaloids through the same intermediates was developed. Acylation of the brominated benzylphenethylamine (13) with α-chloro-α-(methylthio) acetyl chloride, followed by cyclization with stannic chloride, furnished tha key intermediates 4-methylthio-3- phenethylisoquinolin-3-ones (14), which were methylated to provide their methyl ...
