- Total Synthesis of the Didemnins; III. - Synthesis of Protected (2R,3S)-Alloisoleucine and (3S,4R,5S)-Isostatine Derivatives - Amino Acids from Hydroxy Acids
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(2S,3S)-2-Acetoxy-3-methylvaleric acid (3) is prepared from L-isoleucine (2) with 96percent 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 76percent yield and 99.9percent 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.
- Schmidt, Ulrich,Kroner, Matthias,Griesser, Helmut
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p. 832 - 835
(2007/10/02)
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- TOTAL SYNTHESIS OF THE DIDEMNINS - 1. SYNTHESIS OF THE PEPTOLIDE RING
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The 23-membered peptolide ring of the didemnins is formed in a two phase cyclization of a linear ω-amino-pentafluorophenyl ester in 70percent yield without high dilution. (2RS,4S)-2,5-dimethyl-4-hydroxy-3-oxohexanoic acid (Hip) and (3S,4R,5S)-isostatine are synthesized by acylations of trimethylsilyl malonates.
- Schmidt, U.,Kroner, M.,Griesser, H.
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p. 3057 - 3060
(2007/10/02)
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