合成路线1

The cyclization of N-Boc-L-glutamic acid (I) with paraformaldehyde in refluxing DCE gives the oxazolidinone (II), which is benzylated with benzyl bromide and LiHMDS in THF yielding the benzyl derivative (III). The reaction of (II) with CDI in THF affords the activated acid (IV), which is condensed with the protected glutamic acid (V) by means of LiHMDS in THF to provide the adduct (VI). The decarboxylation of the allyloxycarbonyl group of (VI) by means of a Pd catalyst furnishes the compound (VII), which is deprotected and cyclized by hydrogenation with H2 over Pd/C and PtO2 to give the substituted proline (VIII). The lactam cyclization of (VIII) by means of NaOH in methanol, followed by crystallization yields the bicyclic carboxylic acid (IX), which is condensed with the arginine derivative (X) by means of EDC, HOBT and DIEA in THF affording the adduct (XI). The oxidation of the OH group of (XI) with DMP in dichloromethane gives the precursor (XII), which is finally deprotected by a treatment with TFA and PhS-Me. The intermediate arginine derivative (X) has been obtained as follows: The condensation of the fully protected arginine aldehyde derivative (XIII) with benzothiazole (XIV) by means of n-BuLi in ethyl ether gives the adduct (XV), which is then treated with TFA in order to eliminate the Boc protecting groups and furnish the desired arginine derivative intermediate (X).