合成路线1

Partial esterification of (1R,3S)-camphoric acid (I) with MeOH and HCl produced mono methyl ester (II). Further esterification of (II) with isobutylene in the presence of H2SO4 yielded the corresponding methyl tert-butyl ester, which was selectively hydrolyzed with LiOH to provide camphoric acid mono tert-butyl ester (III). From this, intermediate (X) was synthesized by two related methods. Fischer esterification of L-4-nitrophenylalanine (IV) afforded nitrophenylalanine methyl ester (V), which was then coupled with camphoric acid derivative (IV) in the presence of benzotriazolyloxy-tris(dimethylamino)-phosphonium hexafluorophosphate (BOP) to yield amide (VI). Then, reduction of the nitro group of (VI) by catalytic hydrogenation gave aniline (X). In an alternative procedure, N-Boc-4-(carbobenzoxyamino)-L-phenylalanine (VII) was deprotected and esterified with MeOH and HCl to provide 4-(carbobenzoxyamino)phenylalanine methyl ester (VIII). Coupling of (VIII) with camphoric acid derivative (III) as above produced amide (IX). Then, hydrogenolytic removal of the carbobenzoxy group of (IX) yielded aniline (X).