Synthesis

Several syntheses of minodronic acid have been reported,a scalable preparation is described in the scheme. Commercially available acid chloride 71 was first reduced with lithium tritertbutoxy aluminum hydride to the aldehyde 72 at 80°C in 61% yield. Next, reaction of aldehyde 72 with TMSCl and triethylamine generated the corresponding silyl enol ether, which was then treated with bromine to give a-bromoaldehyde 73 in 62% yield. Condensation with 2-amino pyridine furnished imidazopyridine 74, which was hydrolyzed with HCl to acid 75 in 58% yield. Reaction with H3PO3 at 120°C to provide minodronic acid hydrate (XII) in 53% yield.