Enantioselective synthesis of (L)-Fmoc-α-Me-Lys(Boc)-OH via diastereoselective alkylation of oxazinone as a chiral auxiliary |
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Authors: | Satendra S Chauhan |
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Institution: | aBachem Bioscience Inc., 3700 Horizon Drive, King of Prussia, PA 19406, USA |
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Abstract: | Benzyl (2R,3S)-(−)-6-oxo-2,3-diphenyl-4-morpholinecarboxylate (4) was successively alkylated with methyl iodide and 1,4-diiodobutane using a base. In each alkylation step anti-alkylated product formed exclusively. The iodo group was displaced with azide, which served as a precursor for the side-chain amino function. Catalytic hydrogenation with concomitant cleavage of the chiral auxiliary afforded (L)-α-Me-Lys-OH (9) in a total of four steps in good yield. (L)-Fmoc-α-Me-Lys(Boc)-OH (16) was obtained from 9 via regioselective benzyloxycarbonylation. Alternately, (L)-Fmoc-α-Me-Lys(Boc)-OH (16) was obtained via Staudinger reduction of azide (8) in a total of six steps in good yield. |
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Keywords: | Amino acids Asymmetric synthesis Diastereoselective alkylation Chiral auxiliary Regioselective protection |
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