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Synthesis 1989; 1989(11): 832-835
DOI: 10.1055/s-1989-27404
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Total Synthesis of the Didemnins; III. - Synthesis of Protected (2R,3S)-Alloisoleucine and (3S,4R,5S)-Isostatine Derivatives - Amino Acids from Hydroxy Acids

Ulrich Schmidt* , Matthias Kroner, Helmut Griesser
  • *Institut für organische Chemie, Biochemie und Isotopenforschung der Universität Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80, Federal Republic of Germany
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Publication Date:
02 May 2002 (online)

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(2S,3S)-2-Acetoxy-3-methylvaleric acid (3) is prepared from L-isoleucine (2) with 96% retention of configuration. Compound 3 is converted to optically pure methyl D-alloisoleucinate (7) as its hydrochloride salt, via the methanesulfonate 5 and the azide 6 with 76% yield and 99.9% inversion. Subsequent protection-saponification-activation of 7, followed by reaction with the lithium enolate of methyl trimethylsilyl malonate and reduction, yields (3S,4R,5S)-N-(9-fluorenylmethoxycarbonyl) isostatine (12). (3S.4R,5S)-Isostatine is a characteristic unit of the didemnines 1.