合成路线1

The required chiral auxiliary hydroxyketone (II) was prepared from (S)-alpha-pinene (I) either by dihydroxylation with K2OsO4 and NMO, followed by Swern oxidation of the secondary alcohol, or by direct oxidation using KMnO4 under phase-transfer conditions. Condensation of (II) with 2-(aminomethyl)pyridine (III) in the presence of titanium isopropoxide or thionyl chloride as the dehydrating reagents provided the chiral imine (IV), which was estereoselectively alkylated with cyclohexylmethyl bromide (V) and n-BuLi, yielding (VI). Cleavage of the chiral auxiliary of (VI) was carried out by treatment with hydroxylamine hydrochloride. Enantiomeric enrichment of the resulting (S)-pyridylamine was achieved by recrystallization of the corresponding L-tartrate salt (VII). Finally, the amine was condensed with chlorobenzoxazole (VIII) in the presence of NaOAc and Na2CO3 in refluxing methylcyclohexane.