合成路线1

Oxime (VI) was prepared from 4-cyanobenzaldehyde (V) upon treatment with hydroxylamine-HCl and pyridine. The nitrile oxide generated from oxime (VI) and NaOCl underwent a dipolar cycloaddition to methyl butenoate (VII) to produce the racemic isoxazoline (VIII). After conversion of the nitrile group of (VIII) to imidate (IX), reaction with methanolic ammonia yielded amidine (X), which was protected with Boc2O to give (XI). Hydrolysis of the methyl ester of (XI) with LiOH provided carboxylic acid (XII), which was coupled to amine (IV) using TBTU to afford amide (XIII) as a diasteromeric mixture. After Boc group removal by acidic treatment yielding (XIV), its methyl ester group was hydrolyzed with LiOH to afford the corresponding acid. The diastereomeric mixture of carboxylic acids was finally separated by preparative chiral HPLC.