合成路线1

Condensation of N-Boc-L-phenylalaninal (I) with 4-biphenylcarbonyl chloride (II) and KCN in the presence of N-benzylcinchoninium chloride (NBC) afforded alpha-acyloxynitrile (III) as a 4:1 mixture of (2R,3S) and (2S,3S) isomers. Hydrogenation of (III) in the presence of Raney Nickel and tert-butyl carbazate, followed by crystallization of the major isomer from acetonitrile provided hydrazone (IV). Subsequent reduction of (IV) to hydrazine using NaBH3CN and p-toluenesulfonic acid, with concomitant rearrangement of the biphenylcarbonyl group furnished hydrazide (V), which was reduced to the benzyl hydrazine (VI) by means of either BH3 or DIBAL-H. Deprotection of both Boc groups of (VI) with HCl gave diamino compound (VII). Finally, coupling of N-methoxycarbonyl-L-tert-leucine (IX), (prepared by reaction of tert-leucine (VIII) with methyl chloroformate), with diamine (VII) employing O-(1,2-dihydro-2-oxo-1-pyridyl)-N,N,N',N'-tetramethyluronium tetra-fluoroborate (TPTU) provided the target bisamide.