Improved synthesis and preparative scale resolution of racemic monastrol

The Yb(OTf)3 catalyzed Biginelli cyclocondensation reaction of 3-hydroxybenzaldehyde, ethyl acetoacetate and thiourea afforded the corresponding dihydropyrimidine-2-thione, called monastrol, in 95% isolated yield. The chiral resolution of racemic monastrol, a mitosis blocker by kinesin Eg5 inhibition, was carried out on a preparative scale (ca. 100 mg) through diastereomeric N-3 ribofuranosyl amides.