合成路线1

The reductive alkylation of 3-chloroaniline (I) with L-S-trityl-N-Boc-cysteinal (II) in the presence of sodium triacetoxyborohydride produced amine (III). Chloroacetylation of (III) followed by cesium carbonate-induced cyclization of the resulting chloroacetamide (IV) furnished the protected piperazinone (V). The S-trityl group of (V) was deprotected by treatment with silver nitrate and pyridine, yielding thiol (VI), which was subsequently alkylated with ethyl iodide to give thioether (VII). Sulfur oxidation by means of magnesium monoperoxyphthalate in methanol afforded sulfone (VIII). Then, acid deprotection of the Boc protecting group of (VIII) provided the intermediate piperazinone (IX).