合成路线1

The asymmetric 1,3-dipolar cycloaddition of the nitrile oxide resulting from 4-bromo-N-hydroxybenzenecarboximidoyl chloride (I) to allyl alcohol (II) in the presence of (R,R)-diisopropyl tartrate and diethylzinc afforded the (R)-5-(hydroxymethyl)isoxazoline (III). After conversion of (III) to the mesylate (IV), treatment with ammonium hydroxide in a sealed vessel provided primary amine (V), which was then acetylated with Ac2O and pyridine to give amide (VI). Further treatment of (VI) with hexamethylditin and dichlorobis(triphenylphosphine) palladium yielded the trimethylstannyl derivative (VII). Reaction of N-Boc-4-piperidone (VIII) with lithium diisopropylamide and N-phenyl-trifluoromethanesulfonimide at low temperature furnished the corresponding vinyl triflate (IX). Subsequent coupling of (IX) with stannyl derivative (VII) in the presence of tris(dibenzylideneacetone)dipalladium and triphenylarsine gave rise to the N-Boc-tetrahydropyridylphenylisoxazole (X). The Boc group of (X) was then deprotected using trifluoroacetic acid, and the deprotected tetrahydropyridine (XI) was condensed with acetoxyacetyl chloride (XII), yielding the acetoxyacetamide (XIII). The acetate ester of (XIII) was finally hydrolyzed by means of K2CO3 in MeOH.