合成路线1

A new synthesis of FK-156 has been described: The esterification of meso-2,6-bis(benzyloxycarbonylamino)pimelic acid (I) with diazomethane gives the corresponding dimethyl ester (II), which is submitted to selective hydrolysis with a protease from Bacillus licheniformis, yielding the D-monoester (III). The reaction of (III) with PCl5 in dichloromethane affords the carboxyanhydride (IV), which is condensed with glycine 4-nitrobenzyl ester (V) by means of DIEA in dichloromethane to give the dipeptide (VI). The condensation of (VI) with tert-butoxycarbonyl-D-glutamic acid 1-benzyl ester (VII) by means of BOP and DIEA in dichloromethane-DMF affords the protected tripeptide (VIII), which is selectively deprotected with trifluoroacetic acid to the tripeptide (IX) with a free NH2 group. The condensation of (IX) with O-acetyl-D-lactyl-L-alanine (X) by means of BOP and DIEA as before yields the protected final peptide (XI), which is finally deprotected by hydrogenation with H2 over Pd/C in ethanol-formic acid and saponified with 1N NaOH. O-Acetyl-D-lactyl-L-alanine (X) is prepared as follows: The reaction of D-alanine (XII) with NaNO2 and acetic acid gives O-acetyl-D-lactic acid (XIII), which is condensed with L-alanine benzyl ester (XIV) with BOP and DIEA as before, yielding O-acetyl-D-lactyl-L-alanine benzyl ester (XV), which is finally debenzylated by hydrogenation with H2 over Pd/C in ethanol-formic acid to (X).