Diverse synthetic methodologies for the synthesis of various isoquinolinic alkaloids

This research work developed a number of synthetic methodologies for the synthesis of various isoquinolinic alkaloids. They all have in common the use of b-aminoalcohols as the source of chirality operating as auxiliaries or as chiral blocks.

Thus, the employment of (S,S)-(+)-pseudoephedrine as chiral auxiliary enables access to enriched enantiomeric arylglycines, precursors of 3-aryltetrahydroisoquinolines, by means of a synthetic methodology applicable to the stereocontrolled synthesis of such derivatives with a substitution in the 7,8 positions of the aromatic ring of the isoquinolinic nucleus. Also, the aminoalcohol, (S)-(+)- phenylglycinol, has proved to be an efficient chiral building block for access to 1,2-diarylethylamines which, by means of cyclation, lead to optically active 6,7-disubstituted 3-aryltetrahydroisoquinolines.

The convenient manipulation of the synthesised 3-aryltetrahydroisoquinolinic derivatives enabled obtaining a series of chiral berbines, amongst others, (R)-tetrahydropalmatine, (R)-synactine and (S)-xylopinine with high enantiomeric excesses.

Finally, the total synthesis was undertaken of natural aporphinic alkaloid (S)-glaucine employing aminoalcohol (S)-(+)-phenylglycinol as a chiral precursor that helped in the obtention of (S)-laudanosine, on which a process of oxidative coupling was carried out.