A New Approach Toward the Stereoselective Synthesis of Novel Quinolyl Glycines: Synthesis of the Enantiomerically Pure Quinolyl-β-Amino Alcohol Precursors

Abstract

A methodology designed toward the stereoselective synthesis of novel quinolyl glycines is presented. This strategy is based on the cyclocondensation reaction between 2-amino thiophenol 4 and chiral acetylenic ketones of type 3 containing a masked α-amino acid functionality. The initially formed benzo[b][1,4]thiazepine derivatives of type 5, readily undergo sulfur extrusion in refluxing toluene to yield the corresponding 2,4-disubstituted quinolines 6. Subsequent oxazolidine ring opening followed by re-protection in situ of the amino group, led to the corresponding quinolyl-β-amino alcohols 8a - d in enantiomerically pure form and good overall yields. These derivatives of type 8 are in principle suitable precursors for the synthesis of novel quinolyl glycines.