The Mitogenic Principle of Escherichia coli Lipoprotein: Synthesis, Spectroscopic Characterization, and Mitogenicity of N‐Palmitoyl‐S‐[(2R,)‐2,3‐dipalmitoyloxypropyl]‐(R)‐cysteine Methyl Ester

The lipophilic N‐terminal part of the lipoprotein from the outer membrane of Escherichia coli, N‐palmitoyl‐S‐[(2R,S)‐2,3‐dipalmitoyloxypropyl]‐(R)‐cystine, was synthesized via diacylation of L‐cystine dimethyl ester, reduction to N‐palmitoyl‐L‐cysteine methyl ester (7), and alkylation with (2R,S)‐1‐bromo‐2,3‐dipalmitoyloxypropane (8). Alternatively, 3‐bromo‐1,2‐propanediol was reacted with N‐palmitoyl‐L‐cysteine methyl ester (7) and subsequently esterified. As an analogue N‐palmitoyl‐L‐glutamic acid α‐methyl ester (5) was prepared. All products were analyzed by 13C NMR and mass spectrometry. N‐Palmitoyl‐S‐[(2R,S)‐2,3‐dipalmitoyloxypropyl]‐(R)‐ cysteine methyl ester (9) exhibits mitogenic activity towards mouse spleen cells as measured by [3H]thymidine incorporation into DNA. Thus, former investigations having shown the mitogenic principle of the lipoprotein molecule residing in its N‐terminal fatty acid‐containing part are confirmed.