合成路线1

2) The bromination of 3(R)-amino-5-methoxy-3,4-dihydro-2H-1-benzopyran (XV) with Br2 in acetic acid gives the 8-bromo compound (XVI), which is protected with benzyl bromide and K2CO3 in acetonitrile, yielding the dibenzylamino compound (XVII). The reaction of (XVII) with N-fluorobenzenesulfonimide and BuLi in THF provides the corresponding 8-fluoro derivative (XVIII), which is deprotected with H2 over Pd/C in methanol/THF, giving 3(R)-amino-8-fluoro-5-methoxy-3,4-dihydro-2H-1-benzopyran (XIX). The alkylation of (XIX) with cyclobutanone (XII) and sodium cyanoborohydride in methanol gives the dicyclobutylamino compound (XX), which is demethylated by means of boron tribromide in dichloromethane to afford the 5-hydroxy compound (XXI). The triflation of (XXI) with trifluoromethanesulfonic anhydride and collidine in dichloromethane yields the triflate (XXII), which is treated with carbon monoxide, palladium acetate and methanol to give methyl 3(R)-(dicyclobutylamino)-8-fluoro-3,4-dihydro-2H-1-benzopyran-5-carboxylate (XXIII). The hydrolysis of (XXIII) with refluxing 6M aqueous HCl yields the free acid (XXIV), which by reaction with SOCl2 is converted into the acyl chloride (XXV). Finally, this compound is treated with ammonia in dichloromethane to give robalzotan (XIII).