(S,E)-Methyl-2-(3-(2-(7-chloroquinolin-2-yl)vinyl)phenyl)-3-(2-(2-hydroxypropan-2-yl)phenyl)propan-1-ol — “Diol Compound”

Known industry-wide simply as the “montelukast diol,” this chiral quinoline-containing intermediate already carries the drug’s chlorostyryl-quinoline and hydroxypropyl-phenyl fragments joined together. It is converted to the corresponding mesylate and coupled with the mercaptoacetic-acid fragment to complete Montelukast Sodium.