合成路线1

The reduction of L-pyroglutamic acid (I) with NaBH4 gives 5(S)-(hydroxymethyl)pyrrolidin-2-one (II), which is cyclized with benzaldehyde (III) by means of p-toluenesulfonic acid yielding the perhydropyrrolooxazolone (IV). The alkylation of (IV) with 2-cyclohexenyl bromide (V) and LDA in THF affords the corresponding cyclohexenyl derivative (VI), which is reduced with LiAlH4 in THF to give 1-benzyl-3(S)-(2-cyclohexenyl)-5(S)-(hydroxymethyl)pyrrolidine (VII). Elimination of the benzyl protecting group of (VII) with H2 over Pd/C yields the pyrrolidine (VIII), which is reprotected with benzyl chloroformate and K2CO3 to afford the carbamate (IX). The oxidation of the carbinol group of (IX) with Jones reagent or oxygen and platinum black gives the protected proline (X), which is finally deprotected with H2 over Pd/C providing the desired intermediate trans-4-cyclohexyl-L-proline (XI).